what are these fins for?

[potatoe]

i saw a pair of plastic (dolphin tail) looking fins on the same boat and outdrive as mine. they are located toward the lower section of outdrive, above propellar. what do these do? what are they for? thanks

 

[robert graham]

Re: what are these fins for?

You're probably referring to the bolt-on plastic hydrofoil fins that folks sometimes like to add to their cavitation plates to help the boat get up on plane quicker and stay on plane at lower speeds. The work pretty well for a boat that tends to be heavy in the rear and maybe sit lower in the water in the back, because of a heavy outboard motor, rear fuel tanks, whatever. I believe most folks figure them for a stop-gap,add-on solution to a weight distribution problem.

 

[ondarvr]

Re: what are these fins for?

They are normally used incorrectly and this results in a few benefits, but other side effects that people don't like, so many people say they are junk.

Use correctly, and only "if" your boat can benefit from them, you won't experience the negative effects.

A fin or foil will allow you to raise the motor higher on the transom which reduces gearcase drag. It does this by not letting the prop suck air from the surface when accelerating hard at low speeds. Less drag can mean more speed and sometimes better handling. If the fin is dragging in the water at speed then its not set up correctly, this is where all of the negative effects (and opinions) come from.

 

[JimS123]

Re: what are these fins for?

Best $39 I ever spent. My boat is stern heavy because of extra gas tanks and a kicker. No negatives.

 

[5150abf]

Re: what are these fins for?

Run it with it and without it and see which is best, some boats do really well with them an others not so much.

It may have just been put on and isn't really doing anything or it could help quite a bit.

 

[potatoe]

Re: what are these fins for?

it looks like i would have to drill holes through the outdrive to put these fins on. is there another way?

 

[Brewman61]

Re: what are these fins for?

Shop around. Some attach without drilling, If I recall. There are a LOT of companies making these.

 

[JimS123]

Re: what are these fins for?

Reports on the no-drill clip on type are very bad. Its the most expensive model and they often fall off and get lost.

Drill away....your motor is aluminum...it won't rot or rust and when you sell it the new owner won't even see the holes.