hydrofoil fins?

hope this is the right forum, and i have given them the correct name,
anyway, i bought my outboard with these on, its a 25 hp "71".
it will be on a 15ft open top fishing boat which we also use for diving, my question is,....are these things needed? i took them off for fitting my new water pump/impellor/etc, and really not sure of putting them back, if i dont do i need to fill the holes that were made for them?

Re: hydrofoil fins?

The fins can be helpful but something like smart tabs are more effective over a broader spectrum.Usually fins at least partly are a bandage over
a setup problem.Most small boats carry gastanks and batteries at the stern
not an ideal setup these should be moved forward at least to the mid section of the boat.And the motor setup fine tuned.Raise the motor to a point just before venting(cavitation) becomes a problem.Prop selection can also improve boat handling.

Re: hydrofoil fins?

Properly rigged, a hydrofoil can reduce planing speed, get the boat on plane quicker and reduce the amount of trim-out to optimize cruising.

Improperly rigged top speed is reduced and maneuverability reduced.

A well balanced boat does not benefit. Very few small outboard boats are well balanced.

I agree with Steelspike that SmartTabs work a lot better.

Re: hydrofoil fins?

forgive my ignorance but what are smart tabs?

Re: hydrofoil fins?

They help level out, and put you on plain faster.

http://www.iboats.com/Boat_Parts_Ac...250215--submit.Search--submit.x.0--submit.y.0

Re: hydrofoil fins?

I use the Dol-fin "hydrofoil fin/plane" on my boat (a 18.6 Trophy walk around with a 115 Merc). It's set up well for the HP to the boat, proped out great and runs like a top. A 150 HP power plant would probably do better but again... as set up, it works well. It's all about the HP to weight ratio.

That said; the Dol-fin really helped when the boat had more than two people on it. It did well without the hydrofoil but the performance with it is exceptional. Less RPM to get it on plane, stability once up and it holds the cruise at a lower RPM.

I agree that power trim planes/tabs would be better. On this boat (because of how Bayliner configured the transom) you can't install power trim planes. There's a molded protrusion off the transom (for the battery box etc) which does not allow appropriate sized trim planes to sit and work.

Yeah... torqued me off! BUT... the Dol-fin does work well in it's stead.

Re: hydrofoil fins?

i see thank you, better to fit to the boat, rather than stress the engine