Ideal HP outboard for 10' RIB?

[Dockhead]

Before changing motors, you might try adding those hydrodynamic anticavitation wings to the motor you have. I did this a few days ago in Jersey and was amazed at the transformation. Previously the motor would strain up to that point before getting on a plane, and then break through it only with great difficulty and maintain it only with the application of a lot of power. Now there is an almost seamless transition to plane, and much less power needed to keep the boat on a plane. As if half the power of the motor was being wasted, and now being turned into thrust thanks to those wings. You might not need a bigger motor.

[Cheechako]

Yamaha 15 on a 10 RIB served me very well. With 4 aboard and a load the 15 is nice and weighs no more than most 10hp in the same brand... so why go 10?

[twistedtree]

I've got an 11' RIB with a Honda 15hp and feel it's over powered. It planes no problem with 420lbs of people in it. Doing it again, I'd get a 9.9hp.

[SV Demeter]

Thanks everyone. Sounds to me like I should be looking for a 15, ideally 2 stroke, and ideally a yamaha. I suspect my search will take a while as there is no way im spending $2,300 on any outboard, I didnt spend 1/2 of that on dink. Would prbly buy a watermaker first if I was going to spend that sort of dough. Plus the last thing I want is a nice shiny new motor begging to be stolen. Will keep trolling the craigslists and ebay I suppose. We do have a ketch rig so we can use the mizzen boom for hoisting although when not on passage i leave the motor on the dink when on the davits. Simpson Lawrence fixed davits, one of the few things the PO did right, well except for the 7x19 wire lifting cables, swappped that for dyneema a few years ago and been much happier.

Thanks again folks.

[Cheechako]

I wouldnt forego a clean 2 stroke late 90's on up...Evinrude/Johnson 15 if you run across one. Quiet and reliable.

[SV Demeter]

Originally Posted by Cheechako

I wouldnt forego a clean 2 stroke late 90's on up...Evinrude/Johnson 15 if you run across one. Quiet and reliable.

Yeah that sounds more my speed. Maybe I can get a few clams for the 7.5 I have now. Runs great just not enough juice.

[ReMetau]

There are trade offs both ways. If you prefer speed and less weight over fuel economy and having to buy 2-stroke oil, then a 2 stroke is for you.

If you want to save money, then look at a Johnson 15 2 stroke which weighs less than most 10 hp 4 strokes on the market today.

My new 4 stroke Tohatsu with 2 good sized men and 2 smaller women would not get up on plane. If just the two of us, it is fine and has great fuel economy.

[Jbaffoh]

I have a 10'2" Mercury air floor, which is harder to get up on a plane than a RIB. My 2001 Tohatsu 9.8 hp 2-stroke planes with 550 lbs of people and gear with no problem--but there's a catch. I installed Lifters (google them), which are like big trim tabs on the transom. These produce less drag than the foils/wings people attach to their outboards.

To correct a couple bits posted earlier:

Tohatsu 8 and 9.8 share the same block, and weigh 58 lbs. The 15 is bigger and heavier.

Yamaha 9.8 and 15 share the same block and weigh 79 lbs.

The Yamaha 15 2-stroke would be my first choice, but my Tohatsu 9.8 2-stroke is easier to get on and off the boat, and planes just fine.

[Vasco]

Originally Posted by ReMetau

There are trade offs both ways. If you prefer speed and less weight over fuel economy and having to buy 2-stroke oil, then a 2 stroke is for you.

If you want to save money, then look at a Johnson 15 2 stroke which weighs less than most 10 hp 4 strokes on the market today.

My new 4 stroke Tohatsu with 2 good sized men and 2 smaller women would not get up on plane. If just the two of us, it is fine and has great fuel economy.

There is one other factor in going with a two stroke, especially if you're cruising and that is service. For the DIY person it's a lot easier and, if you need a mechanic, you can get them serviced nearly anywhere.

[dirkdig]

15 hp on ours 2 stroke plenty of power.
Good thing is if you sink it you can drain it and off you go easy to fix and tough as.

[gts1544]

In the BVI's, we have a Yamaha Enduro 15HP engine with a 6 gal plastic tank which we fill once a month with 3 or 4 gals at 80 / 1 fuel to oil ratio. It is used by 9 different owners each year for a month each and has been bulletproof. It powers an AB 3.25M RIB and will easily plane the boat with a fair load. It has also been used to drag sailboats of 40' and better into their mooring when they have exxperienced engine problems, a use not to be overlooked. It has been a great engine. gts1544

[Hannah on 'Rita T']

We use a Yamaha four stroke on our 11 foot dinghy, first an AB and now a Genesis and feel the gasoline saving easily justifies the extra weight of the engine. We use the mizzen sheet to hoist it to the rail or lower it on to the dink. With the Genesis, the engine weighs just 20 pounds less than the dink but everything works well. Bought the four stroke on Ebay for $1700 new in the box and its been going for a decade.

[SV Demeter]

The OB issue has become slightly more paramount as my 7.5 crapped out on me Tuesday eve. Was runnning well and somehow fuel hose came discnnected from the tank so motor died. I reconnected, pumped up the ball and tried to restart. Would not start. ended up figuring out that I flooded the motor. Now I suspect I have a carb issue. Motor seems to perpetually flood itself so Im thinking something is up with the float. Will pull the carb and have a look but am now looking for decent used 9.9 or 15.

Im really struggling with the 2/4 stroke decision though. We are a ketch so hoisting motor onto stern rail bracket is not so hard but I certainly prefer lighter motor/dink combo when dragging onto a beach. But 4 stroke means not having to mix gas and better fuel economy, quieter too maybe. ahh decisions...

[Roy M]

Jbaffoh, Thanks for the info on the Lifters. They appear to be very interesting, and at the website price, quite affordable. I am going to be checking them out. For anyone interested: MAXI MARINE - Detachable Planing System for Inflatable Sportboats/RIB (Lifters - special trim tabs).

Sometimes you find some real gems on CF. Thanks again!

[Jbaffoh]

Originally Posted by Roy M

Jbaffoh, Thanks for the info on the Lifters. They appear to be very interesting, and at the website price, quite affordable. I am going to be checking them out. For anyone interested: MAXI MARINE - Detachable Planing System for Inflatable Sportboats/RIB (Lifters - special trim tabs).

Sometimes you find some real gems on CF. Thanks again!

Sorry I didn't post a link--posting from my phone can be a pain in the rear.

The Lifters make a world of difference. Without them, it takes forever to plane with just two people. With them, it planes immediately with three plus gear. I haven't compared top speed with and without.