Doel fin problem

[Baytown.boy]

Installed a doel fin or whales tail as some call it, installed like instructions said, took for a trail run, got on plane real fast but noticed at half or full throttle, boat would not turn at all, a real struggle to turn. Slow down and would turn fine, what is wrong?. Motor is a 1996, 40hp short shaft Johnson. 15 1/2' Alum boat with a 15" transom.

 

[NSBCraig]

Re: Doel fin problem

Could be motor is to low.

 

[dockwrecker]

Re: Doel fin problem

Those fins are notorious for handling problems. Hate em hate em hate em! Smart tabs are the correct fix. Lose the fin!

 

[roncoop75]

Re: Doel fin problem

Took mine off this past week. PO had a bow lifting prop instead of a stern lifter. New prop and fin together were too much. Much improved handling in turns.

 

[Bifflefan]

Re: Doel fin problem

Could be motor is to low.

I was going to say just the opposite.
If the motor is to high and you add the tail when it lifts there is not enough left in the water to make it turn.
Loose the tail, or put a smaller one on, or try lowering the motor.

 

[Baytown.boy]

Re: Doel fin problem

Thanx for yalls help, will take it off.

 

[ondarvr]

Re: Doel fin problem

A fin or foil is not a cure all for every issue a boat may have and is normally only useful after the boat has been set up correctly to use it.

It should not be dragging in the water at speed, that's where all the handling problems come from. To be used correctly the motor should be raised as high as possible, which is what a fin allows you to do. This can improve bow rise, handling, MPG and speed....But only if the motor, prop and hull combination lets you do it.

 

[JimS123]

Re: Doel fin problem

The dynamics of the fin may have changed the action of your motor's trim tab, and/or the tab inadvertently got moved when you installed the fin.

Adjust the trim tab in the direction toward where you are having trouble steering. If that does not solve your problem, raise the motor up on the transom 1 notch and try again.

Doelfins are noted for reliability and performance improvements, but they do require some adjustments on some boats.

 

[a70eliminator]

Re: Doel fin problem

I had one on my 80hp evinrude pushing my 16' MFG. It scared the crap out of me one day when as went into an easy turn, seemed like it suddenly dug in and acted like an airplane rudder and litteraly threw me from the helm, the boat whipped violently to one side didn't turn just sorta leaned over and dug in. I couldn't get that thing off fast enough, I wish now I had saved it because I would maybe experiment with it, at that time I was quite green but I knew enough to eliminate it.

 

[Capt'n Chris]

Re: Doel fin problem

The proper prop is the correct fix!

 

[reelfishin]

Re: Doel fin problem

I had one on my 80hp evinrude pushing my 16' MFG. It scared the crap out of me one day when as went into an easy turn, seemed like it suddenly dug in and acted like an airplane rudder and litteraly threw me from the helm, the boat whipped violently to one side didn't turn just sorta leaned over and dug in. I couldn't get that thing off fast enough, I wish now I had saved it because I would maybe experiment with it, at that time I was quite green but I knew enough to eliminate it.

I had the same experience with one that was on a 16' Bayliner a buddy had years ago.
It had been hard to get on plane with four people onboard, then he added one of those things. The handling went away, the fuel usage went way up, and the speed went down. The only thing he gained was getting up on plane faster.

I've got a pile of those things in the corner which I've removed off nearly every boat I've bought over the years.