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Author Topic:   Preference in hydrafoil products
onlyawhaler posted 05-20-2004 10:53 AM ET (US)   Profile for onlyawhaler   Send Email to onlyawhaler  
I would like to experiement with a hydrofoil on my 150 Johnson to hopefully improve planing times and lessen porposing. I loaded up my 18 OR with a heavy kicker which has undesirable effects.

I see three brands regularly. Doel-fin, Stingray and Turbo. All are different in design.

Any experience out there with any of these brands or others?


kingfish posted 05-20-2004 11:21 AM ET (US)     Profile for kingfish  Send Email to kingfish     
I have personally had sucess with DoelFins on five boat/motor combinations I can think of ranging from a 13'Zodiak/30 HP to a 24' modified V w/175 HP IO. I *think* they are about the simplest and least expensive of the alternatives.
JohnJ80 posted 05-20-2004 11:32 AM ET (US)     Profile for JohnJ80  Send Email to JohnJ80     
I have had ok luck with Stingrays but great luck with the Grand Island Turbo Lift. that fin does not require drilling the AV plate but it is more expensive.

You need to make sure you have the vertical positioning of the motor properly done or the fin will make the performance worse or unstable.

The fin need to ride, at a plane, at the very surface of the water. If it is too low it will provide a lot more drag and can exacerbate problems.


Bigshot posted 05-20-2004 01:16 PM ET (US)     Profile for Bigshot  Send Email to Bigshot     
If engine is low do NOT use a doel-fin, etc. The fin NEEDS to be above the surface a plane or you will lose a lOT of speed and put more stress on the transom.
Joe Kriz posted 05-20-2004 02:44 PM ET (US)     Profile for Joe Kriz  Send Email to Joe Kriz     

What hole is your engine mounted in?
All the way down, 1st hole?
Up one hole, or two?

My 1985 150HP Evinrude is mounted one hole up and have no problems. I also have a kicker weighing 58 lbs.. It does not make sense to me that your boat would porpoise because of a little heavier kicker then mine.

What hole is the Tilt Pin in on your engine bracket? If your pin is out too far, you cannot get enough IN trim on your engine and this may cause you to porpoise. There are 5 holes on the bracket for the pin, mine is in the closest hole to the transom. Some motors do not have this pin or they have been removed. I need mine in this hole because my boat will plow too much if I trim in anymore.

If you cannot trim in enough to stop porpoising, try removing this pin, BUT, be careful in your test runs.


Plotman posted 05-20-2004 08:27 PM ET (US)     Profile for Plotman  Send Email to Plotman     
I'll definately second the reccomendation to make sure the engine is high enough before adding the fin. I would suggest trying one hole up and then two holes (the middle) before adding a fin of any kind.


onlyawhaler posted 05-21-2004 02:05 AM ET (US)     Profile for onlyawhaler  Send Email to onlyawhaler     
Thanks for the comments

When I got my whaler two summers ago, the 150 came with the trim pin in the last hole, closest to the transom. The motor can trim down in this position as far as possible.

Joe, the height is the second from the highest. There are 4 height holes. Only one more and it would be at the highest point.

When I got the boat, it planed quickly (3-4 seconds) and ran terrific. I could dig the nose in by trimming all the way down and plow through the chop or trim up and float over the smooth. It was perfect.

I added late last fall that 8hp Yamaha electric start, electric trim, electric everything 4 stroke. It is probably 140 lbs. Really heavy, I like it, but shocked at how degraded the ride became. Insult to injury, I added a second battery for an electric troller in the rear. Kicker plus battery #2 changed plane time to 6 seconds plus and I have to keep the trim down all the way to avoid porposing. I have lost the ability to trim way down and dig the nose through chop.

I rented a hoist yesterday and raised the motor to the top hole( I was on the third hole before the move). I was hopeful that would help. It made it slightly worse. It is too high and it blows out the prop in sharp turns. I immediately lowered it back to the old hole (3rd up)

I am using a OMC raker stainless 18 pitch. Like everything else, it worked great before the back end load.

I think what is happening is the additional weight on the back (160 plus) has lower the stern, raised the front and changed the whole balance of the boat.

The only thing I can think of doing is lowering the engine from the 3rd hole up down to 2 or the lowest hole on the bottom and trying diffrent hydrofoil products.

Has any one else put a 4 stroke kicker on an 18 OR and had this happen?

Any thoughts?


kingfish posted 05-21-2004 09:00 AM ET (US)     Profile for kingfish  Send Email to kingfish     
Short of repositioning those things that can be repositioned in order to get more weight forward, I think I am hearing that your problem has two aspects, only one of which would be affected by a hydrofoil. A DoelFin type hydrofoil should be above the surface of the water when at full plane; they are helpful in getting up on plane and holding plane at lower speeds, but as was said earlier your anti-ventilation plate needs be high enough that the fin on it is above the water once you have planed. Your motor should be set up that way anyway, and it sounds like it was.

*NO* hydrofoil product will help you with high speed porpoising, as it is not in contact with the water at the speeds where porpoising occurs.

It sounds to me, unless you find that just moving the batteries forward somewhere makes the difference (if you're even interested in trying that), that you need trim tabs. Trim tabs *will* control porpoising.

If you decide to go that route, take a good look at Lenco electrics. I've got them on an Outrage 22 and a Parker 2520 and wouldn't consider anything else.

JohnJ80 posted 05-21-2004 10:04 AM ET (US)     Profile for JohnJ80  Send Email to JohnJ80     
I think this is some pretty good advice.

If you motor is set up properly height-wise and it looks like it was, then trim tabs may be the rignt answer. The only thing to offer on this is it is cheaper to try a fin, but then you have to drill the holes. If your order a Grand Island Turbo Lift - at a cost of $165 (no drilling required), you might be just as well off doing the trim tab installation for not a whole lot more. However, if you are ok with drilling the holes, then you can try it and the out of pocket cost is cheap.

The tabs will definitely solve the problem. As well, they will give you a ton more control over attitude of the hull in a a variety of conditions. I really like tabs for just that reason.

The other thing you could try is changing props to a SS raked and cupped performance prop. But that is a 10% sort of solution and costs about 75% of the trim tabs anyhow.

The biggest, cheapest solution is adjusting engine height, and it looks like you have done that.


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