evil hydrofoil

sergioy

Petty Officer 1st Class
Joined
Apr 14, 2003
Messages
376
After reading a bunch of opinions about hydrofoils on this site, I decided to go ahead and install one on my motor (stingray). I have a 16' Mark Twain with a '63 75 hp Johnson. I don't know if anyone has had any experience with this particular motor with a hydrofoil, but the way it is shaped around the cavitation plate I actually had to rig it with some washers to actually raise the hydrofoil about 1/2 inch from the cavitation plate. In order to get it to fit on there decently. <br />When I put the boat on the water I was really surprised at how the boat got on plane emmediatly, even with three grown adults on it. Before it would have taken forever. But unforunatly the speed was terrible. Now too much of the boat is in the water when on plane (wayy too much). And when one of the adults moved while the boat was moving, it fished-tailed and scared the heck out of averyone.<br />Can I mess with the angle of the foil to get the desired results? Any feed-back would be greatly appreciated.<br /><br />Thanks... :D
 

SystemF

Petty Officer 3rd Class
Joined
Jul 5, 2002
Messages
75
Re: evil hydrofoil

Yes you can mess with the angle. My 73 135 rude is similar. I had to washer my foil to get it to fit. As far as the angle, I assume you don't have power tilt/trim? The tilt/trim is what I used to adjust the boat once on plane. Before I put more weight up front mine had such trouble getting on plane I had to put non adjustable trim tabs on it.
 

jomac

Petty Officer 2nd Class
Joined
May 1, 2003
Messages
195
Re: evil hydrofoil

Think systemF is right! Try adjusting trim angle on motor, sounds like the foil is pulling you down into water at low speeds P.S. Doel Fin makes a 2-piece Foil(smaller) that slips onto either side of cavition plate, works great on older and small motors :rolleyes:
 

binky775

Cadet
Joined
Mar 15, 2003
Messages
13
Re: evil hydrofoil

i lost alot of top end with the dolfin i put on it gets up good but will only do 20mph and chine walks bad have tryed to ajust trim but only gets worse.
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: evil hydrofoil

WS and RM<br />I put doel fins on two different boats.A 15 ft.<br /> aluminum runabout with a 50 evinrude and a<br /> 18 ft. Cobia bow rider with a 120 io.Both responded beautifully planed much easier stayed<br />on plane with less power and were a little more<br />stable.The difference in speed was hard to tell without a tach or speedo.My guess is your fin is too deep in the water.<br /> Doel fin has been around a long time. And has at least 2 sizes.You need to be sure you have the right size and steer away from any fits all fins.
 

sergioy

Petty Officer 1st Class
Joined
Apr 14, 2003
Messages
376
Re: evil hydrofoil

I have gone ahead and adjusted the angle of my foil and the boats seems to have responded to it well. It seems that the angle on the water was much more desirable. Again, the boat planes out emmediately. I'll keep playing with and see what hapens. Thanks for the feedback guys. If the Stingray doesn't work out I will give the Doel fin a try. I have seen them on some older boats and was wondering what they werer called. ;)
 
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