What are these fins for?

[jitts3]

The drive I'll be running came with these. I've seen them before. I know they are aftermarket. Are they worth anything. Usefull, What for.

Am I better off using them or removeing them. They look silly to me.

 

[mwph]

If Im not mistaken, they are cavitation plate extentions or "fins". Supposed to help the boat get up & stay up on plane.

Here ya go...

http://www.westmarine.com/webapp/wc...L=true&storeNum=6&subdeptNum=240&classNum=384

 

[jitts3]

If Im not mistaken, they are cavitation plate extentions or "fins". Supposed to help the boat get up & stay up on plane.

Guess I may want to keep em. They do look goofy though. Thanks.
Not bad asked a question. Got answer in 4 minutes or less!

 

[coolings]

Do you have trim tabs? I would think the whale fin would not be needed if you had trim tabs. A whale fin seems to be the cheaper version of trim tabs.

 

[mwph]

Although the "fins" may help with planing, I think its a somewhat of a stretch to compare them to trim tabs. Tabs can be used to aid in planing however, they are independently adjustable and are primararly used to improve how the boat "sits" once it is on plane. I have yet to master them but rumour has it they can also aid in achieving maximum fuel efficiency.

 

[puck 'n round]

we call them " whale tails " , they act as an airfoil to give more lift to get the boat on plane quicker . Have heard both good & so-so about'em .

 

[Jimmy Buoy]

I tried a pair of these on my 89 268 Dancer and it did help it get up on plane faster, but at top speed with the drive trimmed out a bit it caused problems. The bow would rise too high then fall back down into the water, the boat would slow down a bit then gain momentum again and the cycle would repeat over and over.

It seems to be hit & miss as to how the whale tale effects different size boats.

 

[Asureyez]

Unless ther eis real problem with the boat, tossem and get real trim tabs. These are fine for OB's on dingys.

 

[Nehalennia]

You may as well try them out before you remove them. I'll never put them on a boat though, because If you hit something with them, they'll snap off and possibly take some of your cavitation plate with it.

 

[tobnpr]

They help stern-heavy boats get on plane, and stay on plane at slower speeds.
They do this by creating lift (it's a hydrofoil), but they also create drag so it will cost a bit of speed in the process.

As said above, some boats benefit by them. I had a Doel-Fin on my 22' WAC that helped immensely when we were fully loaded to go offshore fishing. Other boats may not need them. While the boat's out of the water I'd take it off and see how she performs without it. If you feel it's needed, you can always bolt it back on.

 

[jitts3]

Thanks, The boat has trim tabs but like everything else...needs work. Has the old style pump and relays.

Quickly put power to em and nothing. Figure the switch is bad. I will be replacing them at somepoint. I guess I'll trial and error the hydrafoil fins. I was never shue what their original purpose was.
Steve