My old boat has a hydrafoil stabilzer on the cavitation plate. It's only an 85h Evinrude but strong for the size. The former owner placed a hydrafoil on it years ago and said it helped a lot. I'm wondering if I should replace it or take it off because it seems to have curled upward on the ends. Like age and heat has cause the ends to curl upward at about a 15-degree angle. I think it used to be flat when they were first put on.

So on a 16ft size boat with that sized motor, should I keep them on?

Here's a pic

Hydrafoils or doelfins are usually installed to fix problems with a boat and how it runs.  Porpoising, poor holeshot, poor lift, etc are all things they can fix.  You usually loose some topend speed but it's normally a worth while tradeoff.  You can always take the thing off and see how the boat runs without it.  

You said the wrong words......."loose top end speed".  NOW I gotta try it!

I think they used it for hole shot because it was a ski boat.  I think I just might take them off and see if I notice a difference.

All I can tell you is that adding a hydrofoil (Doelfins) to my 60 hp Tracker made a huge difference in my hole shot. As for top end speed or changes in handling, I don't know. It's my first boat, and I was too new at it to look for those nuances.  BTW, when I'm alone, my GPS top speed is 38 mph.  Not bad for a little 17' tin boat.

Not bad indeed.  The 16ft tin I was using had a 55 Yamaha and I got 36mph GPS with two guys, a tournament load, and in rough waters with a head wind.  That boat got 36 loaded or bone dry and empty! haha  It had a hydrafoil on it too.  Hole shot on a tin boat is nothing anyway.  I could plane out in 3-4 seconds but the old tri-hull glass boat I have now takes a bit longer.  I'll trade a bit of hole shot for topend now though.  

Here's a video I just found.  This guy has the same motor I have on a tri-hull ski boat.  Mine's a fish and ski but the weight should be about the same.  He's claiming 47-48mph but doesn't mention a hydrafoil.

Get the right one and with the motor height set properly and they never touch the water on top end and have no affect on top speed.  I run one on my hotrod motors just because they do make a huge difference in hole shot and they also stop a bad blowout problem created just as the boat starts to lay over with one of the props I have.   The boat runs 83 on top end with or without the hydrofoil.  I would strongly recommend the SE Sport 300 though, if you are going to use it on anykind of a performance boat.  I had to cut and inch or two off each side of mine to keep it from digging in during high speed, hards turns.  When it bites the water it causes the boat to want to do things that are not real fun.  

Mine is a "Leading Edge" which is aluminium and it helps hole shot. I'm in total agreement with Way2slow that properly trimmed out there is absolutely no loss in top end speed.

Foils are good for getting a better holeshot and staying on plane at slower speeds.  this is important for speed limits and night fishing for sure.  there is no effect on top end speed because when at WOT the foil is out of the water.  

some say it is a band-aid fix for bad setup. To me a 2-3 second holeshot is a 2-3 second holeshot regardless of how you got it.  Others say they are ugly, I am not in any boat fashion shows....ae you?

I think if they benefit your rig, go for it.

They really excel on underpowered boats and smaller motors, but work great on high performance rigs too.

jb, the hydro foil on your boat is not deformed, it is made that way to minimize water contact for WOT operation especially in a turn.

I used one a few years ago on a bass boat with a GT150 to help reduce transom drop and get on plane quick for shallow tidal water areas.

Question for WtoS, or anyone else..

I have thought about adding one to my 17' procraft / 150 merc.

I dont get alot of bowlift regardless of the prop. My boat runs fairly level at WOT (5800) with a rooster tail even with or above the cowl. Will the foil have any positive attributes while on pad at 55MPH? Will the motor get more leverage on the hull with the foil? Will the foil get more air under the hull reducing drag by lifting the bow higher?

When I am trimming the motor up, will I be essentially trimming the foil out of the water? Will it affect H2O psi?

Thx

Ill tack a question on to this topic too:

I have a 15'10" aluminum boat with a 30hp motor. My normal load is me(190#) two tackle boxes, 70# thrust bow mount tm, 3 series 23 batteries, all in bilge area with two on left and one on right, 7-10 gallons of gas (max 13), and two anchors. This is a console steered boat, not a tiller. I keep the anchors in the under seat storage box to my left. When I run this boat it still leans a bit to my side unless i sit right in the middle on top of my cup holders. My top speed is about 23mph, i don't know what it does gps because I don't have one. My motor is a manual lift type, with a pin and six choices of holes to put it in. When I run at wot my bow tends to dig a bit and it throws alot of water and doesn't do waves well at all. I get about 3mph more speed than at 3/4 throttle, however at 3/4 the bow doesn't dig in and it takes waves 100% better.

Now with my background info and details, here are the questions:

1.Can a hydrofoil do anything for this boat when I run at wot? Like allow me to use all available power but without the negative performance?

2.Is there anything that i can do besides weight manage to get it to ride centered?

Glades,  Are you running an aluminum or SS prop?  If you're not getting good bow lift on your ProCraft, you totally have the wrong prop and other setup issues.  I've never had but two ProCrafts (back in the 80's) but both of those would hold the bow up nice and high.   I'm not much on Mercs and their props but you need to find the one that has a lot of rake (similar to the BRP/OMC Raker).  If your'e not running a jackplate, a 6" - 8" would be a great addition.  For all around use, the 6" might be the better choice, the 8" might make it want to bounce a little when you start coming off plane if you don't get the motor trimed in fairly quickly.   Add a 6" and if you feel you still could use a little more, just add a pair of 2" spacers.   A 6" jackplate and a high rake prop would give you a totally different boat.

At WOT and 55 mph, you should never even know there is a hydrofoil back there

The only thing you should realy notice is the boat should have a lot less bow lift getting on plane and will get on plane much quicker.  Other than that, nothing else should change.  Some say it helps porposing at low speeds but I've never had that problem and have never noticed the foil affecting anything once on plane.

DAWSONH,

Sounds like you need to move your trim pin out another hole or try transfereing some bow weight to the stern.  Foil is not going to do anything for your problem, but help you get on plane.

I had a '86 procraft 16' with a 90 Johnson that porpoise bad when cruising. I put on a hydro foil and got a better hole shot, no porpoising, and didn't lose any top end. I actually think with a higher HP motor you could gain top speed by lifting the bow more.

Thanks for responding. I will give you more information.

I am using a 6" CMC manual jack plate adjusted to 2.5" below the pad. If I go 1/4" higher, I lose water psi when fully trimmed out at WOT.

I use a tempest plus 24P (55 MPH)and a 23P laser2(50 MPH) and a 4 blade michigan 22P (50 MPH). The tempest I bought used and the prop does not have much cup. Should I have the prop cupped?

The boat is a procraft is a fish & ski 1750V which might be a little bit heavier in the nose, plus it has dual consoles.

I think I am expecting to much, I want the bow standing on the motor

at WOT. LOL ( I think I spend to much time dreaming at S&F)

GLADES, yes adding cup will give you more lift.  As far as height, you keep going up until you lose Water PSI, speed, or lift. You don't want to go any higher.  How did it do lower? May get the bow back up.

Be careful adding cup, it's going to drop your rpm. If you don't mind spending a couple hundred bucks, you might give Bob Lipton at 636 949-3121 a call and see what he thinks he can do for one of your props or if he has a better choice. He has worked magic on several for me.

Might want to try droping the motor down to about 3 1/2". One of my rakers starts loosing lift bigtime if I try to run it any higher than that.

I've also never had any experience with a F&S and all that extra bow weight might be hurting you.