Boat Handling / twin or single outboard

Yakmandu · Posted: Sat Sep 08, 2018 9:52 pm Post subject:

A couple related questions regarding twin engines...

Does a dual engine setup negate the need for trim tabs?

How does a dual engine setup affect fuel economy compared to a single engine setup?

This is a very informative thread. Thanks for taking the time to share your experience.

ssobol · Posted: Sat Sep 08, 2018 11:59 pm Post subject:

I don't have dual engines, but I don't see how this would negate the need for trim tabs. In fact, it might make trim tabs more important because of the extra weight on the transom. 2 singles have to weigh more than 1 bigger engine.

NORO LIM · Posted: Sun Sep 09, 2018 12:38 am Post subject:

Chester · Posted: Sun Sep 09, 2018 2:07 am Post subject:

Don't know about now but when our 2005 C-Dory was built twin 40/50 Hondas weighed less than a Honda 90+kicker.
I've been told having twin skegs in the water helps in rough weather especially in a following sea.

PaulNBriannaLynn · Posted: Mon Sep 10, 2018 8:24 am Post subject:

I guess that would depend on the kicker. The little 2.5hp Suzuki is just 30 lbs.

The 40/50 hp Hondas have weighed in at 214 lbs each. 428 lbs for both.

The 2005 Honda 90 weighs 384 lbs. The next generation EFI 90 Honda starting in 2007 weighs 359 lbs.

For comparison of other brands:

Suzuki 50 is 229 lbs. vs Suzuki 90 - 352 lbs

Tohatsu 50 is 209 lbs. vs Tohatsu 90 - 359 lbs

Yamaha 50 is 214 lbs vs Yamaha 90 - 353 lbs

Evinrude E-tec 50 is 240 lbs vs E-tec 90 - 320 lbs.

cmetzenberg · Posted: Mon Sep 10, 2018 8:37 am Post subject:

I like twins for maneuvering and redundancy; i've limped home on one before. I still haven't been able to walk the boat sideways.

robhwa

I've got a Honda 90 with a 9.9 kicker. I had always thought it would be nice to have twins for maneuvering, but what about this...

The Anderson Island ambulance boat has twins, but hit a bar on step and lost use of both engines. They had to paddle the big boat back. Thank goodness they didn't have a patient that was time-critical.

I tip my 9.9 up and lock in place above water when I'm cruising, and it woundn't have been damaged in the same accident scenario. If I damaged the 90, I could them put the 9.9 down and move at displacement speed.

Of course, if I only damaged one of the twins, I might still be able to get on step depending on loading, so could potentially move much faster, but I don't like the idea of being able to damage all of my motors with one miss-step.

hardee · Posted: Sun Sep 16, 2018 12:41 pm Post subject:

robhwa

PaulNBriannaLynn · Posted: Mon Sep 17, 2018 11:57 am Post subject:

I'll argue the difference in maneuvering between twin outboards and a single for a 22' c-dory is overstated. Only at slow speed docking in tight quarters have I noticed any difference at all, and it's pretty minor. The push the throttles in opposite directions to "turn on a dime" trick is pretty cool, but not something that is necessary for a boat this small in my opinion. The c-dory is an easily controlled boat, with either engine configuration.

Of all the reasons we've argued about which is better, I haven't seen an argument I really agree with. There's pluses and minuses on both sides. I've now spent a lot of time behind both setups and I'll state the only reason I prefer twin outboards.....

The sound while cruising. The twins have a lower pitch hum that resonate together. I got used to that sound and it just sounded right to me. The single we have now is great. It's fuel injected and efficient. Its run flawlessly so far knock on wood. But it sounds high pitch and tinny. To me it just doesn't sound right. That's my argument for twins. Also there's a coolness factor. The technical justifications don't make any sense, in my opinion.

hardee · Posted: Tue Sep 18, 2018 12:33 am Post subject:

crowleykirk

We're interested in a Venture 23. Leaning single Suzuki 140 with kicker, thanks Steve, C-Sharp:-)

I'm sure this is covered but haven't found it.

Single say 200 verse twin 90's. This is just an example.

Single 200 runs at much lower RPM than twins. Thus the engine will therotically last longer, and also be much more quiet. Higher PRM's wear an engine out more than lower RPM, or at least faster, not necessarily more. I compare this to motorcycle race engines.

Also time to plane and PRM to plane would obviously be different.

Not saying for better or worse. I like the idea and looks of twins. I also like the idea of a larger single to just chug ginghams along.

I guess it would be interesting to hear comments on sound, fuel burns and maintenance. Times to plane etc.

But I also realize this horse is beyond dead. I'll keep searching:-) If anyone can direct me that would be great. I keep searching single verse twin and it's good info but I haven't found this info.

Thanks so much,
Kirk

Knipet

Doolittle · Posted: Wed Jun 10, 2020 1:41 pm Post subject:

I used to fly quite a bit and my aircraft mechanic used to always say the amount of problems with twin engine aircraft is not double, it is exponentially to the power of 2.

Reliable engines well maintained are going to perform well and even with 95% reliability, 0.95 squared is still a very high number. Like it or not, having two engines long enough, the probability of one of them failing is higher than a single engine.

Note, my mechanic also said that a lot of times all that other engine can do by itself is fly the plane to the scene of the crash!

Knipet · Posted: Wed Jun 10, 2020 2:03 pm Post subject: