Best Hydrofoil

[pmergler]

I am looking to get the most out of my 33 hp o/b 'Rude. I was looking at the "hydrofoils" section of this site; any recommendations to which one is best? I saw prices ranging from $27-$49. Also which is preferred, 1 piece or 2 piece?

Thanks,
Patrick

 

[tashasdaddy]

Re: Best Hydrofoil

imho there are no good ones, the SCREAM i have a set up problem and can't figure out what it is. you engine should be set so the antiventalation plate is even or 1" above the bottom of the boat, and adjust the in and out trim (theres a pin on the transom mount that has several hole) till you get the best performance. what kind of boat is this motor on.

 

[pmergler]

Re: Best Hydrofoil

Boat is a 1965 14' MFG Niagram Custom. I just measured and if the "anti-ventilation plate" is the flat horizontal fin like piece coming off the engine just above the water intake, then it is 3" below the bottom of the transom. It is currently trimmed to the last hole closest the transom out of 4.

So you aren't recommending any of the hydrofoils? I always heard it would push the wake deeper and farther out from the motor creating quicker and better planing.

 

[rickdb1boat]

Re: Best Hydrofoil

I always heard it would push the wake deeper and farther out from the motor creating quicker and better planing.

They will in many circumstances. I've had luck with them on smaller boats and motors I've run. Pops them right up and they stay on plane at lower speeds. Just my experience and it's worth a try. I've always used the Stingray. Always make sure your set-up is correct either way, as explained above...

 

[ezeke]

Re: Best Hydrofoil

I agree with Rick on the planing issues.

Be aware, however, that the fin will create a great deal of drag, so that you will lose at the top end.

The antiventilation plate should be alligned as close to the bottom line of the boat as you can get it without going above the line to start with. Then you can adjust from there.

 

[Silvertip]

Re: Best Hydrofoil

Had them, removed them, and will never have another as long as they keep making Smart Tabs.

 

[Pony]

Re: Best Hydrofoil

I am not sure what brand I have, but it does its job. IMHO I disagree with tashasdady, they DON'T scream set up issues all the time. They sere a purpose just like a trim tab would. There are a lot of setups where it will hinder performance, but some where it will help. I have tested mine both on and off the motor and notice a big difference in the way the boat moves. Without it, my bow goes straight in the air and I have a tough time seeing until I plane out............with it I can plane in half the speed. I tested with gps and I don;t lose any speed with it, so once I get up on plan at WOT its coming out of the water as it should be.

That all being said..............certain motors should never run with a hydrofoil. The older johnny rudes are designed in a matter in which the antiventilation plate rides below the surface if the water. Your 33 depending on the year will probably be like that. That would make the hydrofoil really useless and huge hinderence on your speed and control of the boat.

 

[JB]

Re: Best Hydrofoil

I have used hydrofoils to help a stern heavy boat get on plane and plane at lower speeds. They do not reduce top end when the boat is properly set up and rigged.

Best is the SE Sport 300.

Smart tabs do a lot better job.

Neither will work well unless the engine is at the best height and trimmed properly. Yours is not.

Raise the engine so that the AV plate is 1" to 1-1/2" above the bottom of the boat.

Then reset the tilt so that the AV plate is parallel with the bottom of the boat. If you can't get it exactly parallel set it in the next hole out. If the boat porpoises move it in one hole.

Test her on the water. If you get a decent hole shot and plane easily at about 12-15mph a hydrofoil will do you no good.

You might still consider smart tabs.

 

[Walker]

Re: Best Hydrofoil

I have a Stingray on mine. Does help get up quick but at planing mine isn't in the water.
I'm no engineer but I don't think the airfoil shape has anything to do with it. I think the value of having one on take-off is it places a barrier above the prop and keeps water pressure on the prop from above. In other words it restricts the blow-out from the weakest spot of the water column.

 

[pmergler]

Re: Best Hydrofoil

Thanks everyone....this is great information. And a real help to a newbie!

Another clarifying quesiton....with hydrofoils, are they designed to run just at the top of the water on plane? Pony mentioned that since the older 'Rudes were designed with the AV plates to run underwater, that I would experience detoriating performance. Is this because the hydrofoils always attach to the AV plate and on my motor they would be too much below the surface to make a difference?

Also on my engine setup...this engine has the 5" extension....but if I removed it then the AV plate would be 1 1/2" above the bottom of the boat...I take that would be bad. Currently the motor is clamped down on the transom as far as it can with the base of the U engine mount resting on the transom. When it is mentioned to "raise my motor" should I re-clamp the motor up 3" so the base of the U engine mount is off the transom?

Thanks again or all this great knowledge.

 

[tashasdaddy]

Re: Best Hydrofoil

what it sounds like is you have a log shaft on a short shaft transom.. measure from top of transom the bottom of the v . what year is your 33. i'm running a 1955 15hp with the av plate 1' above the bottom, and great performance. if you have the old clamp on mount that is not designed to be bolted on, you can raise it. and it would be a real pain to try to find parts to convert it back to a short shaft. which is what i realy think needs to be done.

 

[ezeke]

Re: Best Hydrofoil

I think being 1.5" above is way better than where you are now. JB and Walker can set you up there. Just follow what they tell you.

I don't run my boats that way but many do. If I were on flat water I probably would, too.

 

[pmergler]

Re: Best Hydrofoil

I measured and the length of the transom is 20 1/2", the length of the gearcase housing from the AV plate to the top of the exhaust housing where the power head plate sits is 26 1/2". Also the measure from the AV plate to the top of the transom is 23".

This is still the original motor and boat that was purchased from MFG....is it possible they miss matched the length of the motor and the transom?

I guess it sounds like my best option is the re-clamp (yes it is still old style, no hardware) the engine up 3"? I just wanted to make sure there wasn't a problem with that 160 lbs. motor not having the base of the U motor mount resting on the transom.

 

[steelespike]

Re: Best Hydrofoil

It is odd that your 20 inch motor measures 23 inches but::
Yes you can raise it just be sure the clamps have a good grip.If you can do 3 inches safely go to it otherwise go as far as possible.You can cut a piece of wood to support it as you raise it.It is possible to build the transom up as well.

 

[pmergler]

Re: Best Hydrofoil

Cool that is good to know. Now I don't have to worry about trying to find the short shift levers that probably are hard to get now.

And maybe they measure the engine differently then I did....I guess it is possible to that when it was mounted orginially it was done correctly with the AV plate at the bottom of the transom and when my uncle had some loser, drunk mechanic work on it he didn't reclamp it in the right place....I don't know. But I can fix it now. Thanx again

 

[iwombat]

Re: Best Hydrofoil

This discussion raises an issue I've been wrestling with myself. What's the best depth to run the engine on pontoon-type setup where the
transom is in between a twin hull?

Bottom of the pontoon or higher?