Boat has a Hydrofoil from previous owner, should I remove???

[honda460ex]

I bought a 1997 Glassport 17' Fiberglass Bass Boat back in January. The motor is a '83 Mariner 115hp Inline 6cyl. The boat had the hydrofoil on it already from the previous owner. I have noticed the boat never has been one to raise its nose up out of the water much. It's quick to come up on plane, but once on plane the trim doesn't like to push the nose any higher than it has to. My friend who has more experience in boating than I do swears the boat should be planing out better than it is from watching me pass. Says the majority of my hull is still riding in the water when I should be sitting on the back half. My question is, could the hydrofoil be causing this? Or do you think I just have a weak power trim? Or both? The hull is a very light design and my top speed loaded with me and my gear thus far is 45mph.

 

[oops!]

Re: Boat has a Hydrofoil from previous owner, should I remove???

hydrofoils....whale tails ....ect add drag.

but it seems to me that you should have a better speed than that.

im not an ob guy.....but post your info in the prop section.....and give them all the info they ask for.....it might be just a prop issue...

one thing......weight the boat and compair it to factory specs

 

[guy74]

Re: Boat has a Hydrofoil from previous owner, should I remove???

Well, my experience with hydrofoils on my boat tells me that the foil is helping you keep the bow down at take-off. The not being able to get up onto the "pad", is another matter, my boat isn't a preformance type hull, but I have no trouble getting the nose up with a bit of trimming. I run a Se-sport hydrofoil and really like what it does for my setup, but my motor is high enough that the foil is on top of the water at speed. If the motor isn't capable of trimming high enough to lift the bow while planing, you won't get high speeds since your bow will be plowing. All of the bass-boats I have been around are good for wataching the sky til they get up on plane, so I think it is helping your holeshot, but it might be alot of drag at speed if your motor is too low.

 

[honda460ex]

Re: Boat has a Hydrofoil from previous owner, should I remove???

Thanks for your responses. I just took a couple of pictures of the relation between where my lower unit sits and my transom is. Don't know if these pics help tell anything. This is all new to me. And I will post this up on the prop section also to see what I get there. Thanks for the help.

 

[oops!]

Re: Boat has a Hydrofoil from previous owner, should I remove???

your motor is wayyyyy to high......the whale tail is being used as an anti vent plate.....however the top of the prop is half way out of the water.
im suprized you are planing in under 10 seconds with that set up.....you got no bite man !

the anti vent plate should be even with the lowest part of the keel

 

[DynaRider84302]

Re: Boat has a Hydrofoil from previous owner, should I remove???

I have a 1979 21' Taylor Mod VP hull running a Johnson 235. I was told by a guy that raced them back in the day to lose the whale tail and learn to drive the boat.

Previous owner told me the whale tail got the the boat on plane faster and max speed was 50-55.

You Might also play with the motor height...up or down and inch or two after removing the whale tail.

Karsten

 

[honda460ex]

Re: Boat has a Hydrofoil from previous owner, should I remove???

Honestly, the thing planes extremely fast. And I can stay on plane at incredibly low speeds. I would say I can actually be on plane in less than 5 seconds, no lie, no exaggeration... Maybe even a second less than that. It literally lifts on plane right out of the hole when the motor is trimmed down. Most bass boats stand up in the front when they launch, if I want to do that I have to make this thing do that by trimming the motor up. But the bad thing is that motor wasn't the factory motor so moving it down isn't really an option the way it's setup. Moving it up I have some room, but not down. I did post up in the prop section too, but do you think a prop change would help? Like going to a 4 blade from a 3?

 

[honda460ex]

Re: Boat has a Hydrofoil from previous owner, should I remove???

And I do have a trip to Lake Cumberland this coming weekend so i probably will take the Hydrofoil off just to play while I am there. It's only four bolts anyways.

 

[Texasmark]

Re: Boat has a Hydrofoil from previous owner, should I remove???

2nd answer after reading more: Get a high rake ported prop and junk the tail. The ports will help your hole but not interfere with your top end and the high rake will help with the bow lift.

Mark

 

[oops!]

Re: Boat has a Hydrofoil from previous owner, should I remove???

Honestly, the thing planes extremely fast. And I can stay on plane at incredibly low speeds. I would say I can actually be on plane in less than 5 seconds, no lie, no exaggeration... Maybe even a second less than that. It literally lifts on plane right out of the hole when the motor is trimmed down. Most bass boats stand up in the front when they launch, if I want to do that I have to make this thing do that by trimming the motor up. But the bad thing is that motor wasn't the factory motor so moving it down isn't really an option the way it's setup. Moving it up I have some room, but not down. I did post up in the prop section too, but do you think a prop change would help? Like going to a 4 blade from a 3?

props arent your problem....and neither is the whale tail.......you are running a short shaft motor on a long shaft boat......if you look at the keel in pic 2.....see the line of the hull under the drain plug?....now....follow that line to the prop......the prop is half way out of the water the anti vent plate is supposed to be even with the lowest part of the keel.....what that means, is your prop is ventelating....(getting air in where the water is supposed to be) the whale tail is acting like a anti venetelation plate...(the normal plate just above the prop on the out drive.....this si to keep water flowing around the prop so you push water and not air. this is also why you only have a 45 mph top end..
a 19 foot bayliner with a 4 cyl 120 hp will hit 50. (dont get me wrong.....45 is good...but that is a bass boat with a big honkin 6 cyl hangin off the back.)

however......it does look like you have a big alum jack plate on the boat....i would check that thing out and see if the motor can be lowered any more. you will have a totally different boat. the boat will drive the way its supposed to...and your top end will be super. your prop isnt biting water...its biting air.

if you take off the whale tail now.....i think you will find you will have allmost no performance....you will rev the motor, and it will just spray water for 20 feet out the back.

tho it is true that some drives are made for super performance only being half way in the water.....(surface drives) they spin a lot higher rpms than you do and they are made for different hulls than you have.

some of our prop gods will be in tomm morning....
(i am more of a hull tech)....but the real problem is obvious

 

[metriccrescentwrench]

Re: Boat has a Hydrofoil from previous owner, should I remove???

your motor is wayyyyy to high......
the anti vent plate should be even with the lowest part of the keel

That's simply not true. His hull has a pad with a lot of setback, therefore the propshaft should be high. For instance, my Checkmate has a pad type hull and with a 6 inch jackplate I run the PROP centerline at 2-1/2 to 3 inches below the pad (think about how high that puts my AV plate!!!). It looks like his setback is at least as much as mine, and with a pad his engine height doesn't look at all unreasonable. Many many high performance hulls run the engine that high.

IMHO, that old 115 HP engine just isn't quite enough for that boat. 45 is about what I'd expect with a 115 on a 17 ft. boat. I don't know what the max rated HP is for his boat, but I'm betting it's about 150. I'd get an engine closer to the maximum the boat can handle if more performance is what you're after.

As far as the hydrofoil, take it off and see what happens. Can't hurt to try removing it, if you don't like the results it just a couple of minutes to put it back on.

 

[45Auto]

Re: Boat has a Hydrofoil from previous owner, should I remove???

a 19 foot bayliner with a 4 cyl 120 hp will hit 50

Those must be the special Canadian model Bayliners with Clydesdale horsepower, oops! Or maybe you're talking about kilometers per hour?

Down here a 17' Bayliner with a 4 cylinder 135 HP will only do 44 MPH, and an 18' Bayliner with a 4 cylinder 135 HP will only hit 40 MPH (see tests below). Hard to imagine one a foot longer with less HP going 25% faster.

My 18' Bayliner with a 120 OB would barely break 40 with only me and almost no fuel in it. All the 115-120-125 HP outboards in 17' boats on Boattest also barely break 40 MPH.

If the original poster's boat with a 30 year old motor is really doing a true 45 (not speedo) GPS, it would seem that he's actually doing real well for what he has.

It's not hard to find out what it'll do without the whale tail. Undo the 4 bolts, take the thing off, and see if you like it better that way!

 

[Texasmark]

Re: Boat has a Hydrofoil from previous owner, should I remove???

I don't know where my first reply went but if you will look closer, he is on a pad hull (bass boat type thing) with the rear of the pad "set back" (forward) of the transom and in the second picture you can see the jack plate which sets it back even farther.

He has what's called "setback" which the "big boys" have on their 65 mph bass boats. It puts the engine a foot to a foot and a half behind the bottom of the transom which, when the boat is trimmed out properly, very little of the pad is in the water and the boat is pitched up like 15 degrees more or less. With the boat at that running angle, looks to me like he has plenty of "skeg" length to get his prop in the water where it belongs and I'd bet the anti-vent plate is just above the water and the tip of the tail is in the water, causing his inability to lift the bow any more than he currently can. I don't see anything wrong with his setup, nor the length of his mid section. I stand by what I said in my reply above.

Mark

 

[DuckHunterJon]

Re: Boat has a Hydrofoil from previous owner, should I remove???

One thing that hasn't been mentioned - are you propped correctly? What is your WOT RPM at 45 mph? What pitch and diameter prop are you running.

I agree with most of what everyone has said, one thing that does seem off is when you said it planes really quickly, in less than 5 seconds. Now I may just be spoiled with mine (200 HP merc, 21.5' boat), but it's on plane in less than one second, less than a boat length. Again, this could point to being overpropped.

 

[QC]

Re: Boat has a Hydrofoil from previous owner, should I remove???

Wow, train wreck . . .

A Hydrofoil on a bass boat is kinda yucky. I think the height is probably right oops. As a few others have said, on that boat, even with the keel (Pad) would not be right either.

If you take it off, you may need to lower the OB a little, but I would expect slower to plane, higher minimum planing speed, but reasonably higher top speed. That bow and most of the hull should not be in the water. All this assumes that the 115 is enough to take advantage of that hull type.

 

[Maclin]

Re: Boat has a Hydrofoil from previous owner, should I remove???

Those foils/fins can also make it act oddly when turning.

 

[honda460ex]

Re: Boat has a Hydrofoil from previous owner, should I remove???

The boat is rated for a max of 135 hp. It probably does come up on plane quicker than I said. Never really counted, but it happens quick. Faster than my uncles 20 footer with a 200hp merc. At 45 mph the motor revs at around 5,800 rpms. Not at home now to read off the prop, but I know it's a quicksilver, that's it at the moment. And 45 mph WAS read from a gps, not the factory speedometer. Thanks to all of you for your input.

 

[zagger]

Re: Boat has a Hydrofoil from previous owner, should I remove???

Loose the tail, it might take little more time to get on plane but once there you will be able to trim the boat to ride better and gain top end. The previous owner might have tried to pull skiers or tubes and installed the tail for that purpose.