15 HP / 2 St. Yamaha

Does anyone have " first hand " exp. with these fins ( or whatever they are called ) that you often see on smaller outboard motors ? I've talked to a few people at the marina and some swear by them and most just don't know and I certainly would not take the word of the guy selling them .....

We have a Alum. bottom 10.5' RIB but it takes a bit to get up to plane ....

Thanks in advance ....... F.B.

I suspect that you are talking about something like the Doel Fin. These bolt to the cavitation plate and act similarly to a trim tab. They work!!!

I had a 9.9 hp Tohatsu on a 10' RIB. It would only plane with two on board. As soon as I added our dog or even a couple of bags of groceries, it wouldn't plane. The Doel Fin solved that.

Another fix that has about the same effect as the Doel Fin is a flatter pitched prop. When I added both, the boat would easily plane with three people and our dog on board and the engine would operate at a higher rpm which was good for it.

David

I have that motor on my Avon RIB310. It had stabilizers when I got it, but I broke one off when putting the motor into storage. Now with one the only think I've noticed different is that it doesn't plane off as well with a load. So I have some anecdotal evidence of their effectiveness.

Agree with David on the prop. I played with three different pitches on mine, and settled on a 10", but I rarely have more than two people in the boat and am mostly solo. If I was loading it any more I'd go to a 9" and that definitely makes it easier to pop up onto a plane.

I have that motor on my 10' RIB .
As said above, they work and are worth the money.
Definitely easier to plane.

Ex Sailor said:

Does anyone have " first hand " exp. with these fins ( or whatever they are called ) that you often see on smaller outboard motors ? I've talked to a few people at the marina and some swear by them and most just don't know and I certainly would not take the word of the guy selling them .....

We have a Alum. bottom 10.5' RIB but it takes a bit to get up to plane ....

Thanks in advance ....... F.B.

Click to expand...

Doel Fin and derivatives are an absolute must on a RIB. Cheap to. Put it on and you will be forever impressed!!!

Just as an added reference, we have a 10.5' RIB, tried using our 8hp Yami 2 stroke, would plane with two people anything else (dog) nada, tried the fin's and still no good, just not enough HP, but like others have said with 9.9 and fins is a pretty good combo.

Yes!
I had a 10.5'RIB that I bought separately form a Yammy 20 (the dinghy was rated 20hp).
With only me in the boat, initial acceleration was dangerously close to inverting the boat, by driving the transom under the bow.
I put one of those fins on and eliminated that problem, but on initial acceleration with only me in the boat, the bow wouldn't come down to where I could see out. With a sevond person, weight forward, all was well.
I out a set of these: Smart Tabs Trim Tabs Improve Boat Performance on and solved all trim problems immediately. The boat would rise onto a plane with no raising of the bow whatsoever.
I now have a 12' RIB with 40hp that has enough bow weight that I don't need the smart tabs, but I do still have a fin on the cavitation plate to keep the bow from rising.

I have a Yamaha 2 stroke 15 on a 10.5 RIB. No extra fin necessary. Gets up and boogies in very little distance.
I did remove the stock prop and went with the next lower pitch to get there.

On a previous 12 foot aluminum skiff with a 15hp Honda, it would take some effort to get on a plane, and then it would porpoise real bad. Putting a hydrofoil on the motor took care of everything. I have one on my current 12 foot skiff also. Just bought a 15 foot Arima with a 60 hp. , had the same issues with getting on a plane. The hydrofoil took care of it too. Worth the money.

Just keep in mind the hydrofoil is providing lift on the outboard, not the hull. The lift is being transferred to the hull by the motor mounts on the transom. That connection wasn't actually designed for the lifting forces being applied.

Make sure you crank down on your screw clamps.

They come by many names....hydrofoil, doel fin, whale tail. They work well in providing needed lift at the transom to assist in getting on plane.

Same engine here on a WM310 RIB. Like everyone has said, they make all the difference in the world.

The fin did well for a faster planning with a i/o i think 135 hp merc 4 cyl 19' 1984 grady white bow rider.

koliver said:

I out a set of these: Smart Tabs Trim Tabs Improve Boat Performance on and solved all trim problems immediately.

Click to expand...

That website is ridiculous. You use the selector wizard or even the chart to find the trim tabs and both suggest a part number. Easy.

Then armed with the part number you go to the buy now page and all tabs are listed by dimensions with ZERO part numbers to be found anywhere. Ridiculous.

Shrew said:

Just keep in mind the hydrofoil is providing lift on the outboard, not the hull. The lift is being transferred to the hull by the motor mounts on the transom. That connection wasn't actually designed for the lifting forces being applied.

Make sure you crank down on your screw clamps.

Click to expand...

Or through bolt it if you leave the motor on the transom most of the time. That's what I did with my 20hp 'zuki. It helps a lot.