15 HP for Avon 340 RIB

[joe_db]

I just bought a 2003 Avon 340 RIB. I have a 6 HP Johnson that will not work on this boat because it is a short shaft Should have checked before I got it, but too late now. On my current Sportis RIB the engine is good for about 16 knots solo, but 1 more adult or two dogs takes it off plane.

So.... I am looking at a 15 HP 2 stroke Evinrude (Johnson) long shaft. Does anyone have this engine on a 340? The boat is rated for a 25, but that seems a bit excessive for a dinghy that spends a lot of time getting towed behind a sailboat. I am trying not to add too much weight. I would like to be able to still plane with the whole family aboard, which is one wife, one 10 year old boy, and two 50 pound dogs.

[Downhilldai]

A friend of mine runs one with a 15 Merc 2-stroke on a tiller. He's a bit of a lump, but his wife and 2 kids (ages around 8 & 14) are normal size and they struggle to get on the plane. A few years ago, when the kids were smaller, it would plane ok.

There's quite a vee in the 3.10/3.40 hulls, so I'd suggest you go for a 20/25hp

[joe_db]

Got deal on a 15HP Evinrude 2-stroke I couldn't pass up. I'll have to see how she does. I'm going to try something like this:
SPORT MARINE TECHNOLOGIES SE Sport 200 Hydrofoil, Black at West Marine

[joe_db]

I got the boat out the other day for her maiden voyage. Everything went well except the kill switch is bad. With just me the speed was excellent. No GPS, but I'm guessing about 24-27 knots or so I could stay on plane easily at part throttle and the boat handled quite well in relatively flat water. I'll be curious to see how she does with the wife, kid, and dogs.

[NSS]

I have a Rover 340 and have just replaced the 18hp Tohatsu 4-stroke as, with three/four aboard, it really struggled to get on the plane. Mine has console and seating/storage fitted and the 4-stroke engines weigh more than 2-strokes but you may find 15hp struggles with a full load.

Have fitted a new 25hp Suzuki v-twin and it's made a huge difference, even though I can't yet use more than 75% throttle (due to running in schedule).

By the way, I fitted doel fins (hydrofoils) on the Tohatsu motor and whilst it helped, it wasn't enough. I've now added smart tabs to the transom and they not only help get onto the plane, but also seem to make for a more stable ride.

[joe_db]

Update:
The boat flies with 2 adults and one child (about 440 pound of people). I had myself (190 pounds) and one child (90) pounds towing the other 90 some pound child in a tube and it had no issue getting on plane. 15 HP worth of 2 stroke seems pretty decent so far

[devilfishMN]

Originally Posted by joe_db

Update:
The boat flies with 2 adults and one child (about 440 pound of people). I had myself (190 pounds) and one child (90) pounds towing the other 90 some pound child in a tube and it had no issue getting on plane. 15 HP worth of 2 stroke seems pretty decent so far

I plane no problem on my 3.3m SIB with 500 lbs of people with a 1992 15hp mercury 2 stroke with 9" 10.5p aluminum prop on fresh water. Add 150 more lbs and I don't plane anymore, not even close.