My boat, Fan-C-Dory (25ft. C-Dory) has a honda 150 four stroke for a main engine. The engine is a 2006 model and it has a stainless prop. I am the third owner of the boat and have had it for two years now. She ran WOT at approx. 25kts./ approx. 5300rpm. 11.5 gph // 12kts./approx. 3800rpm 5.0 gph. I'll admit we have added a little weight to her with galley stores/v berth bedding/PFD/roof mounted 4man life raft/ additional electronics / plus about 180lbs. lead weight on portside for counter weight. Sooo, maybe a total of 600 to 700 additional lbs. On sea trial (just me onboard) after a bottom cleaning and a 200 hour MAJOR engine service, my boat at WOT only goes 13.5 kts./ approx. 5300rpm/ burns 11.5 gph// only 8.5 kts./ approx 3800rpm/ 5.0 gph/ is it engine timing? spun hub (not experiencing rpm racing)? prop? (not damaged in anyway)? throttle linkage? the tach. is one of those honda mechanical cages (erratic at times) my boat speed is determined by gps/ also relative speeds with radar targets tracked by MARPA and AIS. I have talked with the honda outboard dealer and will have to take it to him to have the codes pulled, however that will be next week and he is about 90 miles away. Meantime, any ideas?? You folks are great, thanks in advance.
Honda 150 four stroke problems???
- Thread starter triton1
- Start date
This is very perplexing in that the engine is developing full rpm, fuel burn is what you recorded in the past, but your indicated speed is lower. If you were dragging something then it would reflect in a lower engine rpm. If the prop was spun, you would probably be over reving the engine and seeing the rev limiter kick in somewhere above 6000 rpm. Not being on the scene, my first inclination is to say the gps was wrong or you were running in a pretty steep current/tide or a combination of both. Did it really look like you were going that slow?
Tom
Tom
13.5 knots is 15.5 mph, and even for a CD 25, a 150 HP Honda should make that boat fly when the engine is running over 5,000 RPM.
I don't think it is a spun prop. Something like that happened to Dave (C-Voyager) in his Marinaut a couple of years ago, but he limped home at slow speed.
It could be that you have too much weight in the stern. Can you get the bow down? If you have too much weight in the stern, it will create drag. Does your boat have trim tabs? If the trim tabs are not working -- are stuck in a down position, that could kick up the bow and create your situation, too. Also, there are some experts on this site that may have something to say about prop pitch from the standpoint that the increase in boat weight may require more pitch.
What bothers me is your statement about all the weight you added from the standpoint that it is my personal feeling that every captain should roughly know how much their boat weighs when fully loaded. In fact, as the captain of a boat, it is that person's responsibility in order to operate a boat safely. So my recommendation is to get the boat in its current configuration weighed, add in the weight of passengers, fuel and water, and see if you are exceeding safe limits. When I had a CD 16 Cruiser with two large adults sitting in the stern, and me in the cabin, it was incredibly difficult and slow (it took several minutes) to bring that boat up on plane at WOT (5600 rpm.) Too much weight was at the stern, and the boat felt unsafe. Never again did I repeat that mistake.
rich
I don't think it is a spun prop. Something like that happened to Dave (C-Voyager) in his Marinaut a couple of years ago, but he limped home at slow speed.
It could be that you have too much weight in the stern. Can you get the bow down? If you have too much weight in the stern, it will create drag. Does your boat have trim tabs? If the trim tabs are not working -- are stuck in a down position, that could kick up the bow and create your situation, too. Also, there are some experts on this site that may have something to say about prop pitch from the standpoint that the increase in boat weight may require more pitch.
What bothers me is your statement about all the weight you added from the standpoint that it is my personal feeling that every captain should roughly know how much their boat weighs when fully loaded. In fact, as the captain of a boat, it is that person's responsibility in order to operate a boat safely. So my recommendation is to get the boat in its current configuration weighed, add in the weight of passengers, fuel and water, and see if you are exceeding safe limits. When I had a CD 16 Cruiser with two large adults sitting in the stern, and me in the cabin, it was incredibly difficult and slow (it took several minutes) to bring that boat up on plane at WOT (5600 rpm.) Too much weight was at the stern, and the boat felt unsafe. Never again did I repeat that mistake.
rich
Speed over water and rpm are generally directly related. If the speed drops so does the rpm for a given propeller, boat, engine, and loading configuration. If you add more weight the speed goes down as does the rpm. The only way for the speed to drop while the rpm stays the same is for the slip in the prop to go way up. In other words, the prop is not advancing through the water as far for each revolution as it was in the beginning. I have encountered that once on a Honda 90 with a Permatrim. When moving up from a 15 pitch prop to a 17 pitch prop. I was generating the same rpm but less speed with the higher pitch prop. At a minimum the rpm should have dropped. My guess in that circumstance was that the turbulence introduced by the Permatrim resulted in water flow problems over the higher pitch prop increasing slip. Unless something changed in the mounting height of the motor, in the prop, or on the motor itself I am at a loss to explain it.
triton 1-
" my boat at WOT only goes 13.5 kts./ approx. 5300rpm/ burns 11.5 gph"
It's developing full/nearly full rpm, but very slow.
You must have enormous drag or weight distribution issues.
At 13.5 knots, it either planing or trying to badly with a big wake.
Sounds like the classic joke condition of the poor fellow who forgot to unstrap his trailer, which was still strapped under the boat. (!)
Could the rubber hub be slipping? Usually the boat will be limited to displacement speed (6-8 mph), if the hub slips freely.
How about motor trim angle? Have you tried to vary that? If the drive unit is tilted too far forward (up under the boat), the bow can be forcefully depressed, making the boat into a displacement type boat plowing through the water, nose down.
Any chance you've flooded a floatation chamber with tons of water? Bow tank? Under floor? Other?
Good Luck, and keep us posted!
JOE. :teeth :thup
" my boat at WOT only goes 13.5 kts./ approx. 5300rpm/ burns 11.5 gph"
It's developing full/nearly full rpm, but very slow.
You must have enormous drag or weight distribution issues.
At 13.5 knots, it either planing or trying to badly with a big wake.
Sounds like the classic joke condition of the poor fellow who forgot to unstrap his trailer, which was still strapped under the boat. (!)
Could the rubber hub be slipping? Usually the boat will be limited to displacement speed (6-8 mph), if the hub slips freely.
How about motor trim angle? Have you tried to vary that? If the drive unit is tilted too far forward (up under the boat), the bow can be forcefully depressed, making the boat into a displacement type boat plowing through the water, nose down.
Any chance you've flooded a floatation chamber with tons of water? Bow tank? Under floor? Other?
Good Luck, and keep us posted!
JOE. :teeth :thup
potter water
New member
Doesn't sound like and engine problem because you get the same RPM and fuel burn rate. You've gotten a lot heavier AND are out of trim to boot. Weighing the boat is a good idea. Or, unstrap the trailer next time you launch
The simplest answer is usually the right answer. You've increased the load!
The simplest answer is usually the right answer. You've increased the load!
Okay, Okay, I'll unstrap the trailer next time and see if that makes a difference. Meantime I have varied the engine trim, played with the trim tabs and have checked the aft bilge for water(none found). I recall getting 23 kts WOT with ALL the extra items I have on it today, plus I had myself and a passenger onboard. I am a hard headed Irishman and I will get to the bottom of this! I'll let you know how the trailer unstrapping turns out. Thanks for all your thoughts................
Sunbeam,
I agree, if the load goes up the RPM generally goes down.
And Joe, it's not the trailer. A boat going that slow burning that much fuel will need to be dragging a tanker, submerged of course.
The solution to this one will be interesting.
I think the first step would be just swap the prop for fun and see if you get a different result. If the prop is slipping in the hub, you would expect the rpm to jump way up. It might be someone playing a joke by changing the gear ratio in the lower end making the motor go fast and prop go slow, but I can think of cheaper ways to have fun.
Tom
I agree, if the load goes up the RPM generally goes down.
And Joe, it's not the trailer. A boat going that slow burning that much fuel will need to be dragging a tanker, submerged of course.
The solution to this one will be interesting.
I think the first step would be just swap the prop for fun and see if you get a different result. If the prop is slipping in the hub, you would expect the rpm to jump way up. It might be someone playing a joke by changing the gear ratio in the lower end making the motor go fast and prop go slow, but I can think of cheaper ways to have fun.
Tom
Les Lampman
New member
Hi Triton1,
I'm going to ask you to suspend belief in your instrumentation for a few minutes.
The first thing I'd like to point out is that your BF150 is NOT developing full rpm at all. It should be propped to turn 5,800 to 6,000 with a normal (your normal) load aboard. Your WOT rpm of 5,300 is way too low for the BF150.
The BF150 has V-TEC, which is variable valve timing. It kicks in at 4,500 rpm and when it does the horsepower curve goes from that point right to the upper right hand corner of the graph. It never falls off like a traditional engine. Rated horsepower (150) occurs at 5,500 rpm but MAX horsepower (160) occurs at 6,000 rpm. In a sense by limiting the rpm to 5,300 rpm you're not even getting the horsepower you paid for; you're certainly not able to take advantage of the V-TEC to reach maximum horsepower.
I am not saying that I think changing props is "the" answer (unless the hub is slipping) to the current issue. I am saying that your boat is "over-propped" and that in and of itself will keep the boat from attaining the performance it should with the BF150 on the transom. In the over-propped condition you don't have a stable base line to work from and it very well might be contributing to what you're experiencing now.
Back the suspension of beliefs (at least those surrounding the instrumentation)...
What you describe isn't possible (this is why I'm asking you not to say "but I saw that" for a moment). It's just physics as applied to boats and propellers and it just comes down to math. The pitch of the prop is the distance the boat will move with one revolution of the prop with no slip of the propeller (and no slip never happens really). We have a mechanical connection between the engine and the propeller via the drive shaft, the pinion gear (in the lower unit) and the prop shaft. Unless one of those things breaks (in which case no power transmission occurs) we always get the same prop shaft rpm for a given engine rpm. That's a given and not subject to interpretation. The prop will also turn the same rpm as the prop shaft as long as the hub in the prop is intact and not slipping.
In order for the boat to achieve 25 kts at 5,300 rpm and later 13.5 kts at 5,300 rpm the prop would have to be slipping a great deal. While that's not impossible it would be highly unusual for it to be repeatable and linear and it wouldn't take long for the hub to completely break free and provide anything more than trolling speed.
It's also not possible to add 600 or 700 pounds to the boat and have it nearly halve the speed and maintain the same rpm and fuel burn. Adding weight increases the load on the engine (meaning it requires more horsepower); for the same speed the rpm will increase, or for the same rpm the speed will drop. And more horsepower always equates to more fuel burned (in the same engine).
It's also way out of the range of "normal" for the CD25/BF150 combo to return the speeds you're talking about even with a great deal of weight aboard. That's not "fact" but given the number of CD25s with Honda BF150s on the transom we know what is typical for that combo and 13.5 kts at 5,300 rpm isn't it.
I'm open for almost anything because strange things can and do happen but I'd say in this case that either something in the drive train has literally broken (and for the life of me I can't think of what that would be) or there's a problem in the instrumentation.
The variables (as I see them at this point, so subject to change) are the tachometer and the prop. You can eliminate the tach by pushing the throttle to the stop and getting your GPS speed (ignoring the tach as you can't over-rev the engine and hurt it). If, with the throttle at the stop (regardless of the rpm), you're getting 13.5 kts then the issue almost certainly has to be with the propeller; either it's slipping in a very strange way or because you're over-propped it's pushed you into a "behind the power curve" situation (the available hp just can't swing the prop).
You can now resume your observations and beliefs! I'm not questioning what you're seeing at all. That said engines, boats, and props behave in certain ways and a behavior that falls outside that norm is suspect. That's the case here. So I'm coming at this from a technician's logic standpoint looking at the mechanical aspects and setting aside the "strangeness" of it which may make me sound skeptical, which I'm not.
It's hard to know what to recommend. Certainly checking the engine with the Honda HDS software will not hurt but I can't think of anything that would result in the situation you describe. Nothing in the EFI system is going to let the engine turn 5,300 rpm (where it always develops the same amount of horsepower) but let the speed drop by almost half.
Given that BF150 is always putting out the same horsepower at a given rpm and that relatively simple math will tell us how much horsepower is required to drive the boat at a specified speed that doesn't leave much for variables. I still suspect you're getting bad data in some way; this in no way implies that you're not seeing what you're seeing, only that something about the data is very suspect (like the tach is set to the wrong pole setting or has gone wonky, or some setting in the gps has changed, etc). Basically, the engine itself isn't going to up and give you half the speed for the same rpm so whatever is happening is happening somewhere other than in the engine itself. It could (remotely) be the prop (slipping or sizing) but it's more likely a data issue.
See if you can grab a Garmin Nuvi or a Tom Tom or a handheld GPS unit and verify that the speeds you're seeing show up on a independent unit. Also check the WOT speed with no regard to the tach reading. I'd also change to a prop that gives you the correct rpm for the engine with your heavier load (should be 5,800 to 6,000 rpm). That should be about a 14 x 15 prop on the BF150 on the transom of a CD25; there are several choices so the numbers can vary but in my experience the BF150 will not swing a 17" prop on a CD25 (especially not a loaded one).
Sorry for the wall of text. Hope it helps at least somewhat.
I'm going to ask you to suspend belief in your instrumentation for a few minutes.
The first thing I'd like to point out is that your BF150 is NOT developing full rpm at all. It should be propped to turn 5,800 to 6,000 with a normal (your normal) load aboard. Your WOT rpm of 5,300 is way too low for the BF150.
The BF150 has V-TEC, which is variable valve timing. It kicks in at 4,500 rpm and when it does the horsepower curve goes from that point right to the upper right hand corner of the graph. It never falls off like a traditional engine. Rated horsepower (150) occurs at 5,500 rpm but MAX horsepower (160) occurs at 6,000 rpm. In a sense by limiting the rpm to 5,300 rpm you're not even getting the horsepower you paid for; you're certainly not able to take advantage of the V-TEC to reach maximum horsepower.
I am not saying that I think changing props is "the" answer (unless the hub is slipping) to the current issue. I am saying that your boat is "over-propped" and that in and of itself will keep the boat from attaining the performance it should with the BF150 on the transom. In the over-propped condition you don't have a stable base line to work from and it very well might be contributing to what you're experiencing now.
Back the suspension of beliefs (at least those surrounding the instrumentation)...
What you describe isn't possible (this is why I'm asking you not to say "but I saw that" for a moment). It's just physics as applied to boats and propellers and it just comes down to math. The pitch of the prop is the distance the boat will move with one revolution of the prop with no slip of the propeller (and no slip never happens really). We have a mechanical connection between the engine and the propeller via the drive shaft, the pinion gear (in the lower unit) and the prop shaft. Unless one of those things breaks (in which case no power transmission occurs) we always get the same prop shaft rpm for a given engine rpm. That's a given and not subject to interpretation. The prop will also turn the same rpm as the prop shaft as long as the hub in the prop is intact and not slipping.
In order for the boat to achieve 25 kts at 5,300 rpm and later 13.5 kts at 5,300 rpm the prop would have to be slipping a great deal. While that's not impossible it would be highly unusual for it to be repeatable and linear and it wouldn't take long for the hub to completely break free and provide anything more than trolling speed.
It's also not possible to add 600 or 700 pounds to the boat and have it nearly halve the speed and maintain the same rpm and fuel burn. Adding weight increases the load on the engine (meaning it requires more horsepower); for the same speed the rpm will increase, or for the same rpm the speed will drop. And more horsepower always equates to more fuel burned (in the same engine).
It's also way out of the range of "normal" for the CD25/BF150 combo to return the speeds you're talking about even with a great deal of weight aboard. That's not "fact" but given the number of CD25s with Honda BF150s on the transom we know what is typical for that combo and 13.5 kts at 5,300 rpm isn't it.
I'm open for almost anything because strange things can and do happen but I'd say in this case that either something in the drive train has literally broken (and for the life of me I can't think of what that would be) or there's a problem in the instrumentation.
The variables (as I see them at this point, so subject to change) are the tachometer and the prop. You can eliminate the tach by pushing the throttle to the stop and getting your GPS speed (ignoring the tach as you can't over-rev the engine and hurt it). If, with the throttle at the stop (regardless of the rpm), you're getting 13.5 kts then the issue almost certainly has to be with the propeller; either it's slipping in a very strange way or because you're over-propped it's pushed you into a "behind the power curve" situation (the available hp just can't swing the prop).
You can now resume your observations and beliefs!
I'm not questioning what you're seeing at all. That said engines, boats, and props behave in certain ways and a behavior that falls outside that norm is suspect. That's the case here. So I'm coming at this from a technician's logic standpoint looking at the mechanical aspects and setting aside the "strangeness" of it which may make me sound skeptical, which I'm not.It's hard to know what to recommend. Certainly checking the engine with the Honda HDS software will not hurt but I can't think of anything that would result in the situation you describe. Nothing in the EFI system is going to let the engine turn 5,300 rpm (where it always develops the same amount of horsepower) but let the speed drop by almost half.
Given that BF150 is always putting out the same horsepower at a given rpm and that relatively simple math will tell us how much horsepower is required to drive the boat at a specified speed that doesn't leave much for variables. I still suspect you're getting bad data in some way; this in no way implies that you're not seeing what you're seeing, only that something about the data is very suspect (like the tach is set to the wrong pole setting or has gone wonky, or some setting in the gps has changed, etc). Basically, the engine itself isn't going to up and give you half the speed for the same rpm so whatever is happening is happening somewhere other than in the engine itself. It could (remotely) be the prop (slipping or sizing) but it's more likely a data issue.
See if you can grab a Garmin Nuvi or a Tom Tom or a handheld GPS unit and verify that the speeds you're seeing show up on a independent unit. Also check the WOT speed with no regard to the tach reading. I'd also change to a prop that gives you the correct rpm for the engine with your heavier load (should be 5,800 to 6,000 rpm). That should be about a 14 x 15 prop on the BF150 on the transom of a CD25; there are several choices so the numbers can vary but in my experience the BF150 will not swing a 17" prop on a CD25 (especially not a loaded one).
Sorry for the wall of text. Hope it helps at least somewhat.
Les Lampman
New member
And more...
If your nav unit also has a sounder incorporated make sure you're seeing Speed Over Ground (SOG) or GPS Speed (Garmin) rather than speed through the water (on some units just called "speed"). Speed through the water is picked up from a paddle wheel that can be slowed, stopped, or just act weird. In several nav units the paddle wheel speed can be offset by a very large percentage to make it match SOG in no-wind, no-current situations, if that setting has been messed with (or it's done strange things) the Speed reading on the GPS could be way off.
Les
If your nav unit also has a sounder incorporated make sure you're seeing Speed Over Ground (SOG) or GPS Speed (Garmin) rather than speed through the water (on some units just called "speed"). Speed through the water is picked up from a paddle wheel that can be slowed, stopped, or just act weird. In several nav units the paddle wheel speed can be offset by a very large percentage to make it match SOG in no-wind, no-current situations, if that setting has been messed with (or it's done strange things) the Speed reading on the GPS could be way off.
Les
potter water
New member
However, if your bodily senses tell you that the boat is traveling almost 35% slower, then you know that the GPS speed is good and that the boat is in fact moving across the water much slower than before. You are talking about a major change in over the water speed. I'm sure you have the experience to be able to sense that the boat is traveling such a major amount slower than before. So I don't think dinking around with other GPS's is going to help you out. Unless you are totally numb to the feeling of the boat through your feet and your senses. On the other hand if your senses tell you the boat is traveling the same speed as before the "problem" then you do have a screwed up instrumentation/GPS thing going.
I can easily tell the difference in feel of STILL CRAZY with 100 or so rpm or even less increase. The boat feels entirely different in the way it moves through the water. In your case, the difference between 13 and 20 is huge. Trust the feel of the boat and if the boat is actually slower, you already know it. I suspect you'll find the GPS speed is fine and that for some reason the boat is just simply slower.
I agree that a slipping prop is going to be a non turning prop in a few minutes at any speed. So that is likely not the problem.
Hope your resolve the mystery and let us know.
I can easily tell the difference in feel of STILL CRAZY with 100 or so rpm or even less increase. The boat feels entirely different in the way it moves through the water. In your case, the difference between 13 and 20 is huge. Trust the feel of the boat and if the boat is actually slower, you already know it. I suspect you'll find the GPS speed is fine and that for some reason the boat is just simply slower.
I agree that a slipping prop is going to be a non turning prop in a few minutes at any speed. So that is likely not the problem.
Hope your resolve the mystery and let us know.
starcrafttom
Active member
This summer I had trouble with my Honda 225. I lost power and speed. I could almost get to full rpm but not the speed. Fuel burn was high. Long story short I had lost a plug. It was dead. The honda runs so smooth that at idle I could not tell that it was missing. I had to unplug each wire one at a time while laying over the motor to feel it missing and could only really feel the miss when I had two plug wires off the motor. Its a long shot but take a look at that.
Les Lampman":3u4d72is said:Hi Triton1,
I'm going to ask you to suspend belief in your instrumentation for a few minutes.
The first thing I'd like to point out is that your BF150 is NOT developing full rpm at all. It should be propped to turn 5,800 to 6,000 with a normal (your normal) load aboard. Your WOT rpm of 5,300 is way too low for the BF150.
The BF150 has V-TEC, which is variable valve timing. It kicks in at 4,500 rpm and when it does the horsepower curve goes from that point right to the upper right hand corner of the graph. It never falls off like a traditional engine. Rated horsepower (150) occurs at 5,500 rpm but MAX horsepower (160) occurs at 6,000 rpm. In a sense by limiting the rpm to 5,300 rpm you're not even getting the horsepower you paid for; you're certainly not able to take advantage of the V-TEC to reach maximum horsepower.
I am not saying that I think changing props is "the" answer (unless the hub is slipping) to the current issue. I am saying that your boat is "over-propped" and that in and of itself will keep the boat from attaining the performance it should with the BF150 on the transom. In the over-propped condition you don't have a stable base line to work from and it very well might be contributing to what you're experiencing now.
Back the suspension of beliefs (at least those surrounding the instrumentation)...
What you describe isn't possible (this is why I'm asking you not to say "but I saw that" for a moment). It's just physics as applied to boats and propellers and it just comes down to math. The pitch of the prop is the distance the boat will move with one revolution of the prop with no slip of the propeller (and no slip never happens really). We have a mechanical connection between the engine and the propeller via the drive shaft, the pinion gear (in the lower unit) and the prop shaft. Unless one of those things breaks (in which case no power transmission occurs) we always get the same prop shaft rpm for a given engine rpm. That's a given and not subject to interpretation. The prop will also turn the same rpm as the prop shaft as long as the hub in the prop is intact and not slipping.
In order for the boat to achieve 25 kts at 5,300 rpm and later 13.5 kts at 5,300 rpm the prop would have to be slipping a great deal. While that's not impossible it would be highly unusual for it to be repeatable and linear and it wouldn't take long for the hub to completely break free and provide anything more than trolling speed.
It's also not possible to add 600 or 700 pounds to the boat and have it nearly halve the speed and maintain the same rpm and fuel burn. Adding weight increases the load on the engine (meaning it requires more horsepower); for the same speed the rpm will increase, or for the same rpm the speed will drop. And more horsepower always equates to more fuel burned (in the same engine).
It's also way out of the range of "normal" for the CD25/BF150 combo to return the speeds you're talking about even with a great deal of weight aboard. That's not "fact" but given the number of CD25s with Honda BF150s on the transom we know what is typical for that combo and 13.5 kts at 5,300 rpm isn't it.
I'm open for almost anything because strange things can and do happen but I'd say in this case that either something in the drive train has literally broken (and for the life of me I can't think of what that would be) or there's a problem in the instrumentation.
The variables (as I see them at this point, so subject to change) are the tachometer and the prop. You can eliminate the tach by pushing the throttle to the stop and getting your GPS speed (ignoring the tach as you can't over-rev the engine and hurt it). If, with the throttle at the stop (regardless of the rpm), you're getting 13.5 kts then the issue almost certainly has to be with the propeller; either it's slipping in a very strange way or because you're over-propped it's pushed you into a "behind the power curve" situation (the available hp just can't swing the prop).
You can now resume your observations and beliefs!
It's hard to know what to recommend. Certainly checking the engine with the Honda HDS software will not hurt but I can't think of anything that would result in the situation you describe. Nothing in the EFI system is going to let the engine turn 5,300 rpm (where it always develops the same amount of horsepower) but let the speed drop by almost half.
Given that BF150 is always putting out the same horsepower at a given rpm and that relatively simple math will tell us how much horsepower is required to drive the boat at a specified speed that doesn't leave much for variables. I still suspect you're getting bad data in some way; this in no way implies that you're not seeing what you're seeing, only that something about the data is very suspect (like the tach is set to the wrong pole setting or has gone wonky, or some setting in the gps has changed, etc). Basically, the engine itself isn't going to up and give you half the speed for the same rpm so whatever is happening is happening somewhere other than in the engine itself. It could (remotely) be the prop (slipping or sizing) but it's more likely a data issue.
See if you can grab a Garmin Nuvi or a Tom Tom or a handheld GPS unit and verify that the speeds you're seeing show up on a independent unit. Also check the WOT speed with no regard to the tach reading. I'd also change to a prop that gives you the correct rpm for the engine with your heavier load (should be 5,800 to 6,000 rpm). That should be about a 14 x 15 prop on the BF150 on the transom of a CD25; there are several choices so the numbers can vary but in my experience the BF150 will not swing a 17" prop on a CD25 (especially not a loaded one).
Sorry for the wall of text. Hope it helps at least somewhat.
Les,
Thank you for your technical explanation; very well written and explained! I agree with your physical facts and just maybe getting some erroneous readings from my instrumentation? I dropped Fan-C-Dory off at the Honda dealer today and they will be pulling engine codes tommorrow. He felt it was significant that my fuel totalizer was off by 10 gal. on my last fill-up. It may suggest a fuel injector problem. He feels it is an engine problem and will explore ALL possibilities until he comes up with a solution to my performance problem. He pointed out that he may not get a code indicating the problem, however he has many parts and systems in the shop that he could temporarily exchange, in order to eliminate causes. I told the dealer many c-brats are as curious as I am and will be standing by for the final resolution! As soon as I know, I will pass it on to my fellow c-brats. Les, thanks again for your insights and excellent explanations.
Robert
Captains Cat
New member
Robert, hope you have a good dealer you can trust. Exploring ALL the possibilities, pulling all codes, swapping out parts etc (my Navy Techs used to call that "easter egging") gets very expensive at $85 an hour or whatever he charges. Swapping out parts particularly to me means he has no idea what's wrong but as long as you're paying for his time, he'll spend it. I love timing lights and carbs but those days are gone! :wink: Most, I would hope are good and trustworthy but some Brats have found some who are not.
Now, if you don't have a bunch of expensive computerized analyzers, you can't do it yourself. There are a few folks I would trust, my mechanic is one of them and Les is another, even though I don't live close enough to use EQ Marine.
Good luck, let us know how it turns out.
Charlie
Now, if you don't have a bunch of expensive computerized analyzers, you can't do it yourself. There are a few folks I would trust, my mechanic is one of them and Les is another, even though I don't live close enough to use EQ Marine.
Good luck, let us know how it turns out.
Charlie
journey on
New member
I'll throw in my freebies.
First, there is a direct mechanical drive between the engine and the prop shaft when it's in gear. That gear shift engages a set of dogs in the lower end. So, if the prop isn't slipping the prop is turning its allotted RPM.
So if the boat isn't moving but the prop is, then you're pushing a lot of water. If I try to get Journey On ( a 25) up on plane without using the trim tabs, it's a heck of a fight. I know because sometimes I forget to lower those tabs, but they remind me quickly. So, you can check the operation of the trim tabs with the boat out of the water. Don't forget to check the tab oil reservoir, aft stdb hatch in the cockpit floor.
With Journey On loaded for cruising, I need those tabs to get on plane more than when it's empty. And she goes a lot slower, though better than 13-14 knts. And BTW, I know when I'm going 25 knts, the boat bounces a lot. Doesn't do that at 15 knts.
Also, Ray, 13.5 kliomoters/hr is 8 mph. Remember you multiply kph by 0.6, not divide.
Anyway, good luck,
Boris
First, there is a direct mechanical drive between the engine and the prop shaft when it's in gear. That gear shift engages a set of dogs in the lower end. So, if the prop isn't slipping the prop is turning its allotted RPM.
So if the boat isn't moving but the prop is, then you're pushing a lot of water. If I try to get Journey On ( a 25) up on plane without using the trim tabs, it's a heck of a fight. I know because sometimes I forget to lower those tabs, but they remind me quickly. So, you can check the operation of the trim tabs with the boat out of the water. Don't forget to check the tab oil reservoir, aft stdb hatch in the cockpit floor.
With Journey On loaded for cruising, I need those tabs to get on plane more than when it's empty. And she goes a lot slower, though better than 13-14 knts. And BTW, I know when I'm going 25 knts, the boat bounces a lot. Doesn't do that at 15 knts.
Also, Ray, 13.5 kliomoters/hr is 8 mph. Remember you multiply kph by 0.6, not divide.
Anyway, good luck,
Boris