Outboard Hydrofoil fins - do they really work ?

affinite

affinite

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I have a Suzuki DF6 4 stroke outboard and a suzumar airdeck inflatable.
The rig has never performed well and, despite changing the prop, and is particularly dissapointing when we want to get up on the plane.
One up it flys but its like riding a bucking bronco and two up only gets on the plane when running downhill ;)

So I was wondering about trying those bolt on hydrofoil fins.

Do they actualy work as claimed - can they help get the boat on the plane ?
Do they help with stability once on the plane?
Is there a downside to using them ?

If Y to above, why are they not fitted as standard ?

Thanks
Steve
 
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We had an inflatable floor Avon dinghy and a 5HP 2 stroke Mariner engine with Hydrofoil fins and it was impossible to get up on a plane, the engine wasn't powerful enough. We changed to an Aluminium floored dinghy and it planed easily but only with one person on board. Aluminium floored dinghies are much lighter than GRP floored and what we saw was that with an 8HP engine it will plane easily with two people. We didn't buy a bigger engine because we were heading back to the UK in three months and intending to sell the boat. I do think Hydrofoil fins work, also they are not fitted to new engines because it would increase the cost and it's a competitive market.
 
We cut out a thin piece of ply and covered in glass cloth and painted it. Bolted it through the top of the existing anti-cavitation plate. It is bigger than any of the commercially purchased plates. It works incredibly well. The boat comes up on the plane quickly and stay there with the revs backed off. It is impossible to flip with the plate fitted. The boat is a 9ft Caribe rib with 9.8hp two stroke. Have had this fitted for nine years. I tried it last year without the plate and it was horrible.
 
We fitted fins to our DF6 and they did help on 2.9 ply floored Waveline inflatable. Best solution though was to get rid of the Suzuki and buy a 2 stroke 9.8 Tohatsu which is the same weight and it will now plane with 3 on board.
 
GrahamM376 said:
We fitted fins to our DF6 and they did help on 2.9 ply floored Waveline inflatable. Best solution though was to get rid of the Suzuki and buy a 2 stroke 9.8 Tohatsu which is the same weight and it will now plane with 3 on board.
Click to expand...

If anyone has a 9.8 Tohatsu to swap in Dodecanese - I'll snap their hand off ;)
 
GrahamM376 said:
We fitted fins to our DF6 and they did help on 2.9 ply floored Waveline inflatable. Best solution though was to get rid of the Suzuki and buy a 2 stroke 9.8 Tohatsu which is the same weight and it will now plane with 3 on board.
Click to expand...

Are you sure? Suzuki DF6 is 25kgs and a 2 stroke 9.8 Tohatsu is 42kgs, I have both!
 
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