Twins on a C-25

matt_unique

New member
This may be stupid question...Based on a typical installation, is it possible to trim one engine out of the water while the other is still down? I use twins on a commercial passenger boat, but it's the only twin installation I've ever used. In our commercial boats the installation would not enable one engine out with one still down.

Is it possible to get up on plane using one 90 if the other was not working for example? Would the stress on the transom be damaging if running one engine with the other off whether trimmed up (if even possible) or all the way down?

Thanks

--Matt
 
My impression is that there would be no damage to the transom. I suspect that you could plane the 25 on one 90 hp engine, because the boat will plane at a fairly low speed. However, I suspect that you would be pushing the engine by lugging it. The problem is that you would prop a dual engine set up with a higher pitch prop. The single engine would be over propped. If you were to change out the prop, then it is quite possiable that you could push the boat at a low plane safely.

It would depend on the steering system and the liquid tie bar vs a solid tie bar. I suspect that there is a bit of stress on the Sea Star hyraulic steering by running with one engine all of the way up. I don't trim the idle engine all of the way up in the Tom Cat when running on a single, but I only run at up to 7 knots.
 
Just to experiment, I've run my boat up on only one engine with the other tilted out of the water. I can get up to about 16-18 knots at WOT. But like Bob says, the prop is too high pitched to run as a single, I believe I was at or slightly below the bottom recommended rpms, not positive though. At below planing speed, like 6-7 knots, should work fine with no problems.

BTW, I routinely tilt up one engine while running if I get seaweed on one of them (temperature alarm sounds), just shut it down, tilt it up, seaweed clears, tilt it back down, start and go. Very sweet!
 
My intent is to get a sense of the true advantages of twins. If I could not run planed off, what would be the advantage of twins vs. single with a kicker?

I'm a fan of twins for the idea of redundancy and some handling advantages. (Even with the engines close together as on the C-25, there are still handling advantages). In my commercial capacity, we run in high current (but of course not planed off) and if we lost and engine, the other would easily push the boat. For my recreational purposes I would need to be able to run on plane for the twins to have an advantage.

Thanks
 
Ah, the endless debate, moved up to the CD25! We had twin Honda BF40s on our CD22, and decided on a single BF150 on our CD25, which took Daydream from Washington State to Alaska and back - we have recently added a BF15 kicker for the redundancy factor. Honestly, either way is great. We could not plane the CD22 on a single 40. I suspect what everyone is telling you about a single 90 is probably correct.

matt_unique":3bnseufq said:
For my recreational purposes I would need to be able to run on plane for the twins to have an advantage.

Thanks
 
matt_unique":2o3ov11y said:
My intent is to get a sense of the true advantages of twins. If I could not run planed off, what would be the advantage of twins vs. single with a kicker?

I'm a fan of twins for the idea of redundancy and some handling advantages. (Even with the engines close together as on the C-25, there are still handling advantages). In my commercial capacity, we run in high current (but of course not planed off) and if we lost and engine, the other would easily push the boat. For my recreational purposes I would need to be able to run on plane for the twins to have an advantage.

Thanks

Ah, that first sentence only applies, if in fact, there is an advantage to twin eninges and I believe at best it's arguable and situational.

If you ask a person who is an avid hiker how you should outfit youself you're likely to get a list long enough to preclude carrying it without some conditioning. If you ask and audiophile what you should purchase for a sound system it would likely scare your wallet to death. The gist of this is the more time one spends exposed to a particular pursuit the more one is exposed to specific situations; if you solve the immediate one you're off to solve the next.

My point is that someone who's been boating for a long time will have 100 different reasons for choosing a specific setup in order to respond to problems or observations of the past. Someone just starting might have a couple of reasons based on what they've read, heard, or studied.

Twin engines only offer an advantage to those folks for whom they seem to offer advatages. In other words, it's situational to some degree and a personal choice to a large degree based on experiences of the past (good or bad).

To respond to your question regarding the ability to run at planing speed on one engine...it generally isn't vital. If it is in your particluar operation (and I can think of valid situations) get twin 135/150's (not a good choice on the CD25 however). The arguement for twins versus a single in this situation isn't that one of the twin engines can run home at normal cruising speeds but rather you can run at a much higher speed than on a kicker (after all you do have 90hp available versus perhaps 15hp) but more importantly, in my opinion, because of the reserve horsepower you're able to deal with much stronger currents, inclement weather (say lots of wind), and waves. I can say with certainty that there are many times when a CD25 on a 15hp kicker can not make headway due to headwinds, headseas, or contrary currents. This would ordinarily never be the case running on a single 90. You're also likely to run about twice as fast on a single 90 versus a kicker which halves the travel time if you're going to find technical assistance.

Now the real question is...how much this all means if where you boat you're seldom 15 or 20 miles from any safe haven? Especially given, with today's modern engines, that it's highly unlikely that one will fail you in the first place.

And then there's the question of money. The CD25 runs perfectly fine and quite nicely on a single 135hp or 150hp engine. A typical 150 will cost in the neighborhood of $12,500 (this will vary a lot depending on what the dealer includes in the price; mostly this number is just here as a relative indicator). Since, to the best of my knowledge, no manufacturer is making a 25" (extra long) 75hp engine the next logical choice for twins is a pair of 90s. With this setup you're going to chew up the better part of $20,000. There's a high likelihood that you'd add a kicker to the single and that would add in the neighborhood of $3000 to bring the single/kicker total to $15,500. Still, a $4,500 difference which is a bit more than what an installed C-80 system with radar runs. So, given that the single main engine will never likely suffer a breakdown (it's certainly possible, just not probable), that you do have a kicker if you need it, and that the difference in the price of the twin versus single/kicker setup would pay for the charplotter/gps/depth sounder/radar setup which would you rather have if you don't boat miles and miles and miles from the nearest place of safety or technical assistance?

What changes the flavor of the whole debate is location and perception. If you're boating offshore or in places like southeast Alaska where you have to be self-sufficient then I believe there's an awfully good arguement for twins. It's a bit like a belt and suspenders and that's where perception comes in. Unless you're getting paid for it I assume you're out in the boat for pleasure. If that's the case you want to have fun and that includes (at least in my household) keeping the family happy too. Therefore, if you feel better (happier, more comfortable, etc) with twins hanging on the stern that's the better choice if for no other reason. If you think they just look great and cost difference isn't a factor that's as good a reason as any (they are for fun after all). They may make docking and handling in tight areas easier but that depends as much on the operator as the fact that there are one or two engines on the stern.

If you fish a lot (and slow troll as we do in the Pacific Northwest) there's a pretty good arguement for a single and a kicker, especially if you like to be in the cockpit and set up a rear station to control just the kicker (the steering at the second station controls the main engine which is tied to the kicker for trolling but the shift & throttle, key switch, etc controls only the kicker in this scenario).

Bottom line...if you have a situation based on operating location or strong personal preference you already know the answer for you is going to be twins. If you're not sure it's a pretty sure bet you don't need them. You may still choose to go that way if the money difference isn't an issue, if you like the idea of it, if you like the looks, etc but it's hard to make the arguement that they're really as important as they might be for, say, offshore or remote area operations. Really, there is no right or wrong and truthfully not much in the way of a techincal reason for choosing twins versus singles since the boat operates well either way (though from a very technical standpoint the single engine is better for the reduced weight on the transom).

Underscoring the bottom line...make sure it makes you smile. I see absolutely no reason to spend the kind of money it takes to purchase a boat these days if it doesn't bring a smile to your face everytime you see it. Get what makes the most sense for you and your family. All a talking head like myself can do is add color commentary. :lol:
 
As Pat and many others will conclude, it's really more of a personal decision. You can do a search on this site and you'll find many discussions on the pros/cons of each. My boating is 95% offshore, 20-50 miles generally. This is my first boat with twins and I love them, maintenance of 2 vs 1 is a very small chore compared to the value I get from them.

I find handling with the twins in close quarters is great notwithstanding the engine spacing. Seems to work just fine, can turn on a dime even in wind, takes a bit of practice to make it look good though -- I'm still learning. I value the twins in big seas when the weather and everything seemly turns bad. I've shut down one engine purposely to check maneuvering and headway ability in 6-8 ft seas with a 2 ft chop. Handled beautifully, the wind and chop are your biggest enemies to making course. Gas mileage is very close to a large single, slightly less I'd say, I get 2.5 nmpg average, but really depends on boat loading and conditions.

I've had to come back with a kicker once (15 hp on a 19 ft boat) in mild seas (2-3 ft, 12-15 knot winds). I could not make headway upwind, but fortunately the marina I was heading for was mostly downwind. I didn't like this feeling of quasi-control of the boat.

So, like I said, it's a personal choice. I'd tend to go twins if you're doing a lot of offshore boating well away from safe havens like I do, otherwise a single and kicker should serve you well.
 
I have also spent time reading through the previous twin threads. Sorry I did not search first.

I certainly omitted the fact that a 90 will power the boat through most any conditions, even if not capable of planing, where a 15 may indeed not be able to do that in seas or winds. Now that I am considering the next boat, I will have to try to plane off the commercial boat with one single 90 running - or basically see what happens as a good measure. We practice flame outs in various conditions but not for max speed with both vs. 1 running.

I was double checking the weight numbers. Using Honda as an example, a 200 EFI weighs 599 lbs sans prop, a 15 kicker weighs 116 lbs. Total weight 715 lbs.

Twin 90 EFI's weigh 359 a piece or 718 total. (Note 20 hp reduction).

A single 150 weighs 485, adding the same 15 kicker weighs a total of 601 lbs. (Note the 30 hp reduction compared to twins).

There is no weight advantage to the single 200 with kicker (but 20 hp advantage). Compared to the single 150 with kicker, there is a 117 lb weight advantage over the twins (but with 30 less hp).

Anyway that is interesting....

Now....why can't C-Dory offer a "two seperate 50 G tanks" option for owners who want to run twins to address the fuel issue? Does not seem that it would be much in the way of cost or effort to add a fuel vent/line.

Fuel contamination is a valid argument for sure. However, each engine would have it's own filters and fuel water separators. The fact that one dies does not automatically mean the other will die based on the fact that you now have 4 filters for your "power system" vs. 2 filters with a single engine.

Prop damage is another nemesis for sure. The props have some distance apart, you can certainly hit one prop and not touch the other though I agree in close proximity you may hit both.

I'm usually loaded heavy with dive gear and my farthest site is 23 miles from the mainland (where my trailer would be), and 15 miles from the nearest island. I sometimes cross from the mainland to the island (15 miles) at night. While I have Tow Boat US for insurance, sometimes the weather (or your schedule) is such that you do not want to wait an hour on the hook...assuming you have enough line to anchor in your depths.

Most of my time is spent within 15 miles of my marina.

Thanks for letting me think out loud with you here. It helps with the process.....

--Matt
 
Sorry Les, we were writing at the same time our "letter crossed", I didn't mean to step on anything you said -- and it appears I didn't, thank goodness... :roll: You're thoughts are much more complete than mine on this subject since I haven't driven or spent any time on a CD-25 with a single to compare. Thanks.
 
As always, Les gives wonderful and sound advice. I come from a little different prospective in small motors. I spent many years on a high freeboard 26 foot sailboat with a 5 hp outboard and it always got us there, all be it slowly. I have pushed 62 foot, 30 ton motorsailor with a 4.5 HP outboard (against current) at 2.5 knots, and with a 25 hp outboard at 5.5 knots. So I have been comfortable using small motors as kickers (I used a 3.5 hp as a kicker on the 22 C Dory.) I happen to own a new 15 so I will use it on the CD 25. What matters is time. If you have to get the boat back, then yes, the 90 will push the boat much better against wind and seas. If you have plenty of time, you can seek shelter or run parallel or off from the seas with a smaller motor. Also as Les says, the modern outboard is a very reliable motor--some of the Suzi's have been documented at 7000 hours in commercial service without failure.

As for fuel--a very good idea is to have parallel fuel systems, with diversion valves, so you can change a filter and still run the engine. All of my diesel vessels had this type of system, and it would be easy to put on any C Dory. The chances of one tank being contaminated and the other not is very unlikely, since you will usually fill both tanks from the same source. If fuel is suspect, have a glass jar and put a cup in that before putting any in your tank.

Props: we always carry a spare, and I have been known to change an outboard at sea--not real easy (depending on conditions) but it can be done. I am not sure that the "one orop" damaged and the other not is necessarilly a rule. I have seen a number of vessels bend up two sets at once.

Interesting that various parts of the country use different terms. You use "Plane off". I have always used "come up on a plane". It appears that the "plane off" is more of an eastern term.

But as Les says, it is what makes you happy--and it twins are what you want, then get them!
 
New Hampshire Guy":gk2p2flp said:
Now that you've mentioned diving, maybe the Tomcat would be worth a look...

Hook me up with a $20K discount on the Tomcat and I'm there! :wink:

No doubt, the Tomcat would be the ultimate boat for my purposes....but....$20k more for the boat and need for much larger tow vehicle puts it out of my desired price range.

I need to ride in a C-25 with twins then compare the ride to a single (similarly loaded to see how it feels).

--Matt
 
The Cockpit in a Tom Cat is a bit bigger than the 25, plus a real good dive ladder and the Armstrong bracket makes an excellent dive platform. I am sure that you could dive off the CD 25, but that second engine would intrude on the space in the well where you would step going to the platform with your gear. For diving I would strongly consider a single--plus a custom dive ladder. In your waters you will be wearing bulky gear and it will be more difficult to get around than with only a lycra suit or bathing suit.

I believe Dive Cat is still available (in Calif)--almost a new boat, really loaded and rigged for diving--at far more off than a new boat less 20K--worth shipping or a drive across country. There was also a TC 255 with twin 115 outboards (a bit older motors, and perhaps underpowered with a full load, but still could be a good dive platform, and I believe it was under 90K.

Plus then there is no question about the twins!

Bob Austin
 
My son and I are both divers. I use a 4-step ladder over the side, sit on the gunwale and step outward off the ladder right at water height and slip into the water, works good. When coming back on board, we take off our BC and gear, clip it to our mooring line strung between the rear and forward-center cleat, throw our fins on board and climb aboard on the ladder. Works for us.
 
I used to roll off the side of my boat, then tie off the gear at the surface to climb aboard, then hoist the gear into the boat.

I added a x-mas tree ladder to my small platform and was able to walk out wearing doubles for about 2 seasons. I re-enforced my polymer (plastic) swim platform with multiple ss backing plates, fingerglass, etc. but in fact last time out it broke. I weigh 170, and my doubles rig with drysuit, etc. adds another 150 lbs for a total of 320 lbs. Lesson learned on that...you need a full swim platform across the stern with massive load distribution to handle climbing out with doubles. From now on, and most likely with the next boat, I will resume ditching gear at the surface, climbing out, then lifting the gear in. I would love a Tomcat for sure...but I just struggle with adding $20G added to the C-25 cost plus a new tow vehicle.

Back to the C-25, sorry again for posting with the twins vs. single question. I am very curious about the possibility of planing on a single 90 though. If I read correctly above, one owner can do it.

--Matt
 
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