Hydrofoil ... Good or Bad?

[luckyinkentucky]

I've had a Speed XP hydrofoil on my 94 Evinrude Vindicator 200 for the past several weeks. I used it a total of 4 times on the boat, and I must say I am not impressed. The first time I used it I couldn't really judge if it was the 2 ft. high waves on Kentucky Lake or my Hydrofoil which was causing me the problems, but I gave it another chance.

The second time I used it I noticed I had to trim the motor higher than usual to keep the drag down. Normally I have a worry free ride without it, but with it I have to tune everything just right to get it to top end. Also, if the trim isn't in the exact spot it should be with the hydrofoil on it wants to hold down the front end of the boat to the point of porpoising.

I took it off, and am going to see how it runs without for awhile. I will get back, and let everyone know what I find out.

In the meantime what are your experiences and opinions on hydrofoils? I've had several mechanics tell me that they are a waste of money.

 

[WillyBWright]

Re: Hydrofoil ... Good or Bad?

I think you'll find that pretty much every mechanic is of the same opinion, not to mention the motor manufacturers. If they were so great, they'd incorporate them into their motors. Heck, not one single outboard manufacturer even offers such an upgrade. That should be enough in itself to give one pause.

Every mechanic I've ever known kinda chuckles at them when they roll in, except for the one doing gearcase work. Then it adds labor to the bill of it has to be removed to manipulate the gearcase. It's another 10 minutes for the ones I have to remove and reinstall (not a tack-on charge, I work on the clock). Holding devices don't work with whale tails on, and most need to be removed just to get the gearcase on and off because the installers don't install them quite right. On big outboards, either the boat it's on is really fast or really heavy. That much force on 4 little screws through 1/8" thick cast aluminum? I don't think so.

Hydrofoils work best on flat bottom boats where you can mount the motor high enough for the antiventilation plate to clear the water once the boat is on plane. On most other applications, it adds drag that can slow you down and seriously mess with handling.

 

[Dhadley]

Re: Hydrofoil ... Good or Bad?

A fin is a tool. It allows you to do other things to improve performance. If your set up was maxed out and you simply bolted it on you'll most likely see less performance. The fin in itself won't do much, if anything to improve performance. It will allow you to do other things that will increase performance.

Generally speaking if you don't have a jackplate, you can't take advantage of what a fin might offer. Then you get into size and shape. We've used fins on race and high performance boats with great success. But not those ones you typically see.

 

[Captain Jeff]

Re: Hydrofoil ... Good or Bad?

Good post... I was considering removing mine which came with the boat. It seems to require a much larger turning radius but the boat is pretty stable in rougher seas.

Some manufacturers advertise improved gas mileage, any idea how this could work? It seems that these devices would add more drag and actually decrease fuel economy.

 

[ondarvr]

Re: Hydrofoil ... Good or Bad?

This question comes up frequently, mostly with negative comments, but I've never seen a fin used for what they actually can do, people bolt them on and expect that with no other changes it will somehow solve a bunch of problems. Many times there aren't even any real problems to solve, they just expect it to make everything work better, but what happens is just the opposite and they blame the fin. Peolple try to use a fin because they cost less than what they really need, which is trim tabs.


In adjusting the setup on my boat (19' CC, 200HP evinrude), I was able to raise the motor and get another 150 free RPM's with a small increase in speed, but when I did this, the cheap prop I have would ventilate badly during accelaration. I didn't want to spend $400.00 or $500.00 on a new SS prop for a boat that only gets used a few times a year, so I bolted on a fin that had been sitting in my shop for years. This made a huge difference, the prop now gets a good bite and I'm planing much faster, not because the fin is in the water holding the bow down, but because the prop has water around it, not air. My fin is out of the water at planing speeds so it has no affect on handling and it "won't" do what trim tabs are designed do. If I have time this summer I may try to raise the motor higher to see if I can get more out of it after putting the fin on.

 

[Molaker]

Re: Hydrofoil ... Good or Bad?

Sometimes they just might solve a problem...

I have a 19' 1970 Deckboat with a '82 Johnson 140hp on it. The boat is almost a flat bottom boat - very very shallow 'V' forward and the beam is nearly 8'. At the transom, it is flat. The motor sits as low as the transom will permit and the anti-ventilation plate is only slightly above the bottom (1" maybe). When I first tried the boat/motor combination I could hardly make a turn without it ventilating, even at less than WOT. Trying to pull up a slalom skiier or tube was a joke. In desparation, I added a "hydrofoil" and it solved the problem. Yes, it took a few mph off, but it still goes faster than most slalom skiiers and tubers want to be pulled.

Granted, I chose the cheap way out and did not go with an expensive jack plate, but I'm satisfied with the results. Dhadley is right, it is a tool. In my case it seemes to be the right tool.

 

[luckyinkentucky]

Re: Hydrofoil ... Good or Bad?

Actually I was wondering how the prop affected the hydrofoils. From what they guy I bought the boat from said I am set up for maximum performance as is. I have a 13 1/4 X 25 SS Shooter prop, and I usually get to plane a little faster than the bulky Bayliners do. I was just looking for the 'perfect' holeshot for when I tow skiers, but from what I've seen my 20' 95 Skeeter 200SL does a lot better job of towing skiers than most of the Bayliner type boats out there anyway. Like I said, I was just looking for instant plane, and that's not going to happen unless I get a Cigarette boat with twin 1075SCi Mercury Racing Engines.

 

[Molaker]

Re: Hydrofoil ... Good or Bad?

Like I said, I was just looking for instant plane, and that's not going to happen unless I get a Cigarette boat with a 454 Big Block.

Just start your ski run with a lot of slack in the rope...

 

[ondarvr]

Re: Hydrofoil ... Good or Bad?

A prop change sounds like a better option for pulling skiers.

 

[Dhadley]

Re: Hydrofoil ... Good or Bad?

Exactly. The fin is a tool that allows you to run a higher X dimension. That's where the increase in efficieny come in. Run the fin too low and it will hurt efficiency.

 

[MercGuy]

Re: Hydrofoil ... Good or Bad?

I have experience installing Hydrofoils on 3 boats (I owned one of them).

My experience is that they are an absolute miracle on underpowered boats. I once made the mistake of buying a 16ft Maxum with a 50 HP Force outboard. I had that thing propped beyond max RPM at WOT and it would not plane. I installed a fin and BINGO !! it would plane with confidence. Of course it wasn't a speed demon, but the fin was the only thing that made that boat even usable.

I've since installed fins on 2 other boats (for friends) each of which was underpowered, and the fin greatly improved the the overall owner satisfaction.

Having said that I currently own an 18ft SeaRay with a 115 Merc, and I've never considered putting a fin on it, she runs great as is

 

[Cap'n Dave64]

Re: Hydrofoil ... Good or Bad?

I just put a stingray hydrofoil on my Starcraft 16ft Starfire with a 60hp 4stroke Yamaha. Here's what I think:

Pros: Gets on plane faster, holds plane at lower speed (15mph vs 12), much smoother ride thru chop, much less roll in turns, quieter (less wave slap), lower bow at any speed, less steering grab when hitting waves at an angle, less wake at transitional speeds

Cons: 0.5 - 1mph loss at WOT, one more thing to hit something with (not that that has happened)

Oh yeah that top speed loss? only applies to flat calm conditions. Otherwise faster with hydrofoil. It's like a brand new boat. It seems to me that people with light fairly fast boats like mine have had the best results, I'll gladly swap 33mph top end with 34mph top end for all the other things. BTW tested the boat on consecutive days in exact same conditions and boat loads (only diff was the foil) and was blown away.