low power C-Dory/ Marinaut

M

marco422

New member
I have been thinking about my future retirement boat and really like the looks of Toland's new design (if it comes to fruition). I am also mindful of the general upward trend in oil prices, despite the current low price. I am wondering how a low-power engine on one of these boats, or a comparable 22 C-Dory, would perform. What I'm thinking is the minimum motor that would get it up on plane with a normal load under normal sea conditions, without the requirement to move really fast. Maybe, 12-15 knots at 4500 rpm.

Has anyone ever tried a 40 or 50 on these boats? Obviously it would do fine at hull speed, but would it be able to get up? What would the disadvantages of "underpowering" the boat be?
 
Most of us with twin 40s will tell you that it's very difficult to 'get up' (if not impossible) with a single 40. I think a 70 would be the minimum single. Having said that I would never consider less than I have (twin 40s).
 
The disadvantages of an under powered boat are many. My last boat was underpowered and it was frustrating. There were some conditions (rougher seas/heavier load) when I could *barely* get up on plane and only with everyone moving as far forward as possible. The engine will work harder (i.e. lugging) and this will shorten it's life. The resale value is also decreased. Depending upon the engines in question, there may be a significant difference in amperage produced for running systems and charging batteries.

There could be situations in rougher seas when insufficient power could prove dangerous, such as an erratic following sea. I have been in situations when I needed to stay ahead of a following wave until it dissipated.

Owners never regret too much power but often regret too little. I don't think you need to install quads on that puppy (he he) but the difference in price for a smaller engine may not be worth the aggravation and other pitfalls.
 
matt_unique":2o3qem3i said:
Owners never regret too much power but often regret too little.
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This along with the rest of matt_unique post is right on. That being said when I was in C-dory search mode I ran across a CD22 for sale with a single 50 Honda. It did get the job done and used little fuel. I may be totally wrong in my memory but I think I remember way back when the factory web site even listed the performance numbers with a single 50. I'm sure someone will correct me if I'm wrong. I had a 75hp on the CD19 and it did well.

Roger
 
I've seen it many times on this forum and by highly respected (by me also) participants that it is very difficult if not impossible to get a CD-22 on plane with a 40 Hp outboard. I have a 2001 CD-22 with two 2002 Honda 40 Hp outboards and my normal load is not light considering all the "stuff" I carry. I've never had trouble getting on plane with one motor in and the other out of the water. 14 mph (gps) at WOT of 4500 rpm The difference I have may be my props which were Solas 4 blade x 12" pitch x 10.8 dia. With both engines in use I got 28 mph WOT 5200 rpm. Last season I re-proped with Solas 4x11x11.1 and top speed stayed about the same (I need to recheck that) but rpm's went up to 5900. Sorry, I don't know how the new props perform with one outboard but I'll check it next season(sometime in May). Since I changed props in mid-season, mileage figures aren't as accurate but the 12" prop got me an average of 4.5 mpg over a whole season and the new 11" prop reduced it to about 4 mpg; next season will be a better test. The reason I went to the new prop is I always do a family trip and upon departure with a heavy load WOT was 4700 rpm with the 12" prop.

Getting back on topic, I think a single 40 Hp would do fine with the right prop if it's made. I think Solas only goes down to a 9 or 10" prop but I would think that would get WOT above 5000rpm which is within Honda's specs. Yes, you don't have lots of power but lots more compared to any displacement boat of similar size. Know where you are going, what you have, what to expect, and think - and you'll do just fine. I would look closely at the Marinaut's weight and deadrise when comparing to CD-22 for Hp performance.

Jay
 
The Evinrude ETEC motors might be a good candidate for saving fuel. They are lighter than 4-strokes and at low speeds they get better mileage due to their lean burn injection.

Another choice for better economy would be a 8-10hp high thrust kicker motor. Red Fox reported about 6 MPG on a heavy 22 Classic using a Yamaha 8hp high thrust kicker. The kicker can be linked to the main for steerage so you have economy at low speeds and still carry the large motor for safety of higher speeds.
 
I have the new Honda90 and a 9.9 kicker. Twin 40's or 45's are also a good choice. The fuel economy with these newer outboards is very good and the place C-dory's fills is all about fuel economy and versatility. Dropping from a 90 or twins down to a 70 or 50hp would make the boat very hard to sell in addition to creating the issues mentioned above.

Now it is true that I tend to zoom around, but some rarely run above the low 4000rpms and others watch their fuel consumption gauges. I would bet these c-dory owners get as good or better MPG, on average, than you would with an underpowered boat.
 
12 to 15 knots (13.8 to 17.3) is a good cruising speed for the C Dory 22--and any boat with more dead rise will not plane at a lower speed. I run my C Dory 25 mostly at 17 knots. You will need a decent size engine to carry these sustained speeds.

I am sure that some boats will get up to 14 miles per hour (incidently one of the problems with GPS speed is that you may have a current with or against you) but if you are running that engine WOT at 4500, you will be lugging the engine, which will not be good for longivity.

Sure you can use a 40 or 50, but the fuel economy will not be any better at a given speed as a 75, and the resale will not be good. If you want to use an 8 hp--that would work at displacement speeds.
 
Chuckpacific":15rxdo97 said:
Most of us with twin 40s will tell you that it's very difficult to 'get up' (if not impossible) with a single 40. I think a 70 would be the minimum single. Having said that I would never consider less than I have (twin 40s).
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There must be several factors that affect the performance of a single twin. An extra 250 pounds hanging off the stern, drag from the unused motor skeg, inefficiency of a motor mounted off-center, etc.

As far as twin 40's or a single 75 being the minimum, I can see that being a good match for the design, but partly that perception is driven by current conditions. If fuel was to syyrocket, our priorities would surely change. I am trying to establish what minimum motor would plane the boat. If you're never planing, you might as well use a displacement hull form which has other advantages.

It seems like a couple of posts here have suggested that a properly propped 40 could do the job. Someone has suggested that a 40/50 working hard will use the same amount of fuel as a 75 taking it easy. Is that true?
 
Fuel consumption is dictated by the amount of HP used at that specific time. For gas engines it is close to 14 hp per gallon of gas per hour. It makes little difference if this HP comes from a 40 hp engine or a 75 hp engine. (there is a little friction with the very large motors, but many times larger motors actually test slightly better at these low planing speeds.

To get a boat on a plane, it requires that the boat has to "climb" over its bow wave--that takes xx amount of HP and is basically the limiting factor here. Shifting weight (human and fixed) can put a bow down, and get the stern up--and get a boat on plane faster. Those of us who grew up waterskiing behind low HP outboards had to do that to get the boats on a plane. We used a 30 hp on a 13 foot boat and slalom skiied. But it required weight shifted foreward, going up on two skiis (more planing surface) and then dropping the extra ski.

Yes, not having the extra weight of the other 40 on the boat would make a difference. Any weight makes a difference, as well as weight distribution. But do you want to cruise with no ice chest, minimal fuel, limited supplies and gear?

Then you have to take into account head winds, (increased resistance), wave patterns, as well as currents etc.

Yes, a round bottom boat, with narrow beam will be more effecient at displacement speeds--but then it will not plane--so no comparisoin.

Give it a try and see how you like it--then report back--you can always hang an extra engine on the stern. But like I said in another post--the cost of fuel is not the greatest cost of owning a boat. For example--storage may be $200 a month--that is $2400 a year--or at $2.00 a gallon for fuel--it is 1200 gallons x 4 miles a gallon--or 4800 miles on the water. There are very few C Dories who go 4800 miles a year on the water! Lets say that you spend $50,000 for a new C Dory. 6% interest (which you used to get on your investment conservatively--would be $3,000 a year-again 1500 gallons of fuel--you get the picture!

Don't give yourself a subprime boating experience because you feel that saving a few bucks on fuel will make a difference!
 
thataway":15cuztig said:
Fuel consumption is dictated by the amount of HP used at that specific time. For gas engines it is close to 14 hp per gallon of gas per hour. It makes little difference if this HP comes from a 40 hp engine or a 75 hp engine. (there is a little friction with the very large motors, but many times larger motors actually test slightly better at these low planing speeds.
Click to expand...

I have always thought that the enrichment of the air/fuel mixture is about the same in any outboard so your fuel use will be related to displacement x rpm. I guess that is saying more or less the same thing, as the horsepower extracted from the fuel is equivalent. But a larger motor running at low rpm is going to be less efficient than a motor running at design optimum-- 75-80% rpm. Not so?
 
I will give you my 2 cents. Sounds like everyone has given logical answers to this one.
I ran a single 50H.P. Honda on my 22 ft. Classic for 2 years here in Alaska. The only good thing about it was the fuel consumption or the lack of. I spent most of my time on the inside sheltered bays and passes where the engine was fine. If the wind and tide were right and I hoisted the mainsail I could get it on plane(I can think of 1 time).
When I decided to fish in the open waters of the Gulf of Alaska things changed. The boat was seriously underpowered and quite frankly scary. In a following sea I could not even get out of my own way. Running the boat at 12 to 14 knots the boat did not have enough power to get off the backside of the swell-it would slow the boat to 6 or 8 knots and make it really squirlly.
The boat was very very lightly loaded and always had 1 person onboard.
I recently upgraded to a 90H.P Yamaha and all these problems disappeared.My fuel consumption went up just a little but it nice to have the power in those situations above.
In short- if you are going to sight see and not in a hurry the 50 will do but for safety reasons go bigger. You will still be able to go slow and monitor fuel with a 90. But when you want to get somewhere just get her up on plane. It is a whole new boating experiance for me-almost like I am in a whole different boat. Sorry for the long post-GO BIG
 
Nice post T-Lats. I'm in total agreement. I've told this story before but will tell it again. When we bought C-Dancer new, we knew nothing about boats and I hadn't discovered this most valuable website of which I could have learned something in advance. So we were persuaded to rig our new boat with a Suzuki 70hp. It made sense, Honda owners choose between the 75hp and 90hp, right? Except what I didn't realize was that the Honda engines were the same, the 75 being the detuned version. With the Suzukis, the 70hp was a smaller engine than the 90 hp. Long story short, we felt very underpowered the first season, mostly because we were overpropped but also because of the smaller engine size. After feeling vulnerable the first season to various conditions, we decided to repower to the Suzuki 90hp and have never looked back. It's nice to know we have the power in reserve when we need it. After finally installing the correct prop on the 70, it did feel much better and would have been adequate but by then we wanted more. It seems as though we made the right choice, especially after seeing a few of those unsold Suzuki 70's for sale at the factory party a couple of years ago.
 
When I bought the Duck 22 cruiser she had a 50 honda on it . We took the boat out through one of the Gulf 's inlets with 3 men on board .Top speed was 16 mph ,She would plane at about 12-14 mph I dont think I saved any fuel because the Honda was screeming at 12-14 mph (5000rpm) or highter . I repowered witha Suzuki 90 got the 6 yr warranty and had pleasant experiences with that eng for 3 yrs then I sold the boat and the reason the couple bought the Duck was the 6 yr warranty and 90 hp . Get the 75honda or the new 70-90 Suzuki motors and be happy
 
Some performance feedback: with our 22 Angler (lighter than the cruiser but same basic hull), lightly loaded and on calm water I was able to hit 17MPH with one Honda 40 at WOT and the other out of the water. I had Permatrims. The boat was definitely lugging the engine at that point and it's nothing I would recommend doing on a regular or long-term basis. I do think a single 70 with a low pitch prop would be OK as long as you went slower and kept it in a reasonable rpm range. Hard to imagine being able to re-sell a CD22 with a single 50 very easily. The single 50 would be fine if you were content withdisplacement speeds and an infrequent emergency burst of speed. Overall, I'd advise against it. Mike.
 
I'll add my two cents to this discussion. I have a 1999 CD-22 with twin Honda 40's (which I love). Lightly and evenly loaded and with Permatrims, I can get up on plane at 11 mph and hold plane at 9 mph. One engine will do this easily.

However, cruising the Erie Canal (where the speed limit is 10 mph), I find that running both motors makes for a much more pleasant ride: the rpms are much lower than with one motor and it seems quieter.

I have tried to ascertain the difference in gas mileage: it seems imperceptible. Either running one motor or two, I get 6+ mpg at 10 mph.
 
Lots of information here. My conclusion is that a 40 or 50 will plane the boat fairly easily when properly propped, but with very little reserve power. It seems like a 70 is a sensible minimum. It also seems that the difference in gas mileage will be negligible: that any engine is going to require about the same amount of fuel to deliver the required minimum horsepower. That would be if the required horsepower is delivered within the efficient operating range of the motor (say at 1500-4500 rpm, higher than idle but less than 80%). Plus, the big increase in output from the alternator is a bonus (triple on the Honda). Oh yes-- and resale value is a big issue...

Thanks for all the input!
 
Over 6 miles a gallon at 10 miles per hour (8.7 knots) is very impressive-- how is that fuel consumption measured? Has anyone else achieved this economy? This means that you are using 1.7 gallons an hour and only using about 24 hp at 2.4 x sq root LWL...
 
thataway":2k88kax9 said:
Fuel consumption is dictated by the amount of HP used at that specific time. For gas engines it is close to 14 hp per gallon of gas per hour. It makes little difference if this HP comes from a 40 hp engine or a 75 hp engine. (there is a little friction with the very large motors, but many times larger motors actually test slightly better at these low planing speeds.
Click to expand...

This reminds me of a question that I've been trying ,with out success , to get an answered. Has anyone ever seen the performance chart for the Suzuki 115. I'm talking about a graft/chart that shows hp and fuel burn at rpm.

Roger
 
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