Mercruiser 470 Hydrofoil problems - Please help.

[kevinstan]

When I got my boat the previous owner gave me a hydrofoil for the outboard part of the engine. He said he removed it because it was put on slightly crooked. When I got the boat I placed the hydrofoil over the holes that were made on the motor to see how it lined up and sure enough - it was about 1 inches cocked sideways from being straight. I wanted to put it back on to try it so I did last weekend at the lake - and upon driving the boat I noticed it was pulling the boat to the left and down into the water like it was dragging something.... I removed the hydrofoil and the problem stopped.

I do want to use a hydrofoil to lower the bow rising when driving, and stern from dropping so fast when slowing down - but I can't imagine how the hydrofoil being 2" crooked would cause this???

Does anyone have any ideas? Or have had the same issue before?

Is it worth me using a drill and making the hole bigger to straighten it up? would this fix the issue?

For what it's worth I couldn't get to the back screw / nut very well and I think it could have still had a little give in it when I tested the boat out - and I was thinking maybe the hydrofoil lifed up about a half inch and could have caused the drag?

I want to fix this and place the hydrofoil on right - any help would be greatly appreciated.

 

[spoilsofwar]

Throw it in the trash, or give it to someone you don't like. They're rarely the solution to anything.

I'd install some trim tabs if you're having issues with excessive bow rise that the drive trim alone can't control.

 

[steelespike]

I have to agree the foil his a bandage at best and a problem to fine tune at the least.
Check out the smart tabs. These need to be applied just enough to be effective.
They are said to control bow rise and reduce no wake speed wander Boat should stay on plane longer as you reduce throttle.

 

[kevinstan]

On my previous boat I noticed a big difference using the stabilizer / hydrofoil - I was wanting the same results with my new boat. Not sure if I want to invest in smart tabs and have to drill holes in the boat to mount them. I already have holes in the drive trim where this hydrofoil was mounted - but the holes are not lined up.

 

[Starcraft5834]

I would agree with Spoils.. toss it out... if you are running a 3 blade prop.. consider moving to a 4 blade.. you will find that will remedy same.. will jump you on plane faster, maintain plane at lower speeds... improve helm control at slower speeds..... overall, if you can live with going 1-3 mph slower at WOT, you will love the 4 blade... benefits outweigh the only downside... that is a loss of a little bit of top end speed. most people are happy with the trade

 

[alldodge]

Find a "good" welder which knows how to weld aluminum and fill the holes up, then re-drill

 

[Newbie@boats]

I put a hydro-foil on my last trophy and it worked EXCELLENT for getting the boat onto plane quicker.....if my new trophy didnt have trim tabs you can bet I would be ordering another one

 

[bruceb58]

I had a Doel FIn that came on a boat that I bought used. In my opinion it made it dangerous. Would cause the stern to slide out on hard turns. Took it off and that dangerous characteristic disappeared and top speed went up.

 

[bruceb58]

Find a "good" welder which knows how to weld aluminum and fill the holes up, then re-drill

Yes...and don't re-drill!

 

[alldodge]

Yes...and don't re-drill!

The OP want's the fin so yes re-drill

 

[bruceb58]

The OP want's the fin

Unless we talk him out of it.

 

[kevinstan]

I am beginning to think I will be leaving them off... Though I really wanted it for the benefit of having it on. Seems better than not to use it and have it on.

 

[alldodge]

Unless we talk him out of it.

I like mine, so I'm not trying to talk him out of it

 

[kevinstan]

I hear more people like it than don't. I may try it again and just use my drill to open the other hole a little more to even up the hydro to make it straight and even instead of crooked.

 

[bruceb58]

No matter what you do, get it welded and then re drill if you really want it. By making the hole bigger you are just asking for the cavitation plate to break off. You are already stressing the cavitation plate as it is using a fin. Making a bigger hole is going to be even worse.