Hydrofoil stabilizer or not?

[bluka43]

I run a 17' 1998 Xpress with a 1998, 90 HP Yamaha outboard. The boat gets up on plane fairly easily and fast enough. The only dislike is then when running 3/4 to full throttle (this is on very calm water), and adjusting the electric trim to where I can achieve max rpm and speed the boat starts to porpoise. I have to trim the motor back down to get it to stop porpoising, naturally decreasing the speed and rpm. I have been reading about the pros and cons of installing a hydrofoil stabilizing fin on the cavitation plate of the motor. Some say speed is lost, which doesn't bother me. I can sacrifice 3 or 4 MPH. I would think that being able to run with less boat in the water and without porpoising would be a better ride and use less fuel. I really don't care to mount stabilizers to the rear of my boat. If I could get some suggestions as to whether the installation of a stabilizer on the motor would help my situation, or is it worth it?
thanks

 

[Bondo]

Re: Hydrofoil stabilizer or not?

and adjusting the electric trim to where I can achieve max rpm and speed the boat starts to porpoise. I have to trim the motor back down to get it to stop porpoising, naturally decreasing the speed and rpm.

Ayuh,... That's How boats work...
Adding a whaletail will only make it worse...

 

[dockwrecker]

Re: Hydrofoil stabilizer or not?

No stinkin' fins!:facepalm::facepalm:no no no no!!
Smart Tabs probably would help.

 

[nlain]

Re: Hydrofoil stabilizer or not?

I had a boat that I ran a Stingray foil on, it made porpoising worse, cut speed, increase fuel consumption. Smart Tabs is the way to go, I have used both, current boat has Smart Tabs, they are worth every penny.

 

[Limited-Time]

Re: Hydrofoil stabilizer or not?

Put it on and try it. In my experience on my boat it made a positive difference. The boat planes at lower RPM/speed with less throttle input. As for top speed I saw no difference by the factory speedo. Load, water conditions and temperature have more effect on my boats top end.

 

[DaNinja]

Re: Hydrofoil stabilizer or not?

Breaking 156th batch of popcorn...

 

[1fishbone]

Re: Hydrofoil stabilizer or not?

Breaking 156th batch of popcorn...

Still counting?

 

[1fishbone]

Re: Hydrofoil stabilizer or not?

I run a 17' 1998 Xpress with a 1998, 90 HP Yamaha outboard. The boat gets up on plane fairly easily and fast enough. The only dislike is then when running 3/4 to full throttle (this is on very calm water), and adjusting the electric trim to where I can achieve max rpm and speed the boat starts to porpoise. I have to trim the motor back down to get it to stop porpoising, naturally decreasing the speed and rpm. I have been reading about the pros and cons of installing a hydrofoil stabilizing fin on the cavitation plate of the motor. Some say speed is lost, which doesn't bother me. I can sacrifice 3 or 4 MPH. I would think that being able to run with less boat in the water and without porpoising would be a better ride and use less fuel. I really don't care to mount stabilizers to the rear of my boat. If I could get some suggestions as to whether the installation of a stabilizer on the motor would help my situation, or is it worth it?
thanks

Somewhere between $4 and $60 to end up with the same or similar results.
They came with boat, I think they looked weird, didn't do much, took em off and left them off.

http://www.iboats.com/Hydrofoil-Sta...2627676--**********.160153150--view_id.217147

 

[steelespike]

Re: Hydrofoil stabilizer or not?

Motor height can affect porpoising a little.Also height will affect a foils action.Yes a foil will get on plane better and likely stay on plane with less power.But you will be dragging at least a portion
of the foil through the water at all times.A foil is a bandaid over a setup that isn't just right.The antivent plate just above the prop should be visable on plane usually ends up about an inch above the bottom.Trim tabs, like Smart tabs, are a better choice.Application/adjustment should be done carefully as excessive pressure can slow the boat.
porpoising;basically the motor/prop lifts the bow but can't keep it up so it repeats.A little less weight in the stern and a little more toward the bow could eliminate it.I've seen light boats say 14 ft that bob when a pilot sits normally in the stern seat but will stop just by leaning forward.
Some boats are more sensitive to porpoising.
There are props with more bow lift but they may slow hole shot.
There are props with stern lift that likely would resist porpoising and improve hole shot.

 

[DaNinja]

Re: Hydrofoil stabilizer or not?

Still counting?

That was just roughly the number of threads that popped up after a quick search of "hydrofoil stabilizer".

 

[rallyart]

Re: Hydrofoil stabilizer or not?

I am a big fan of hydrofoils in many situations. However, if your boat currently is getting up on plane well I would not recommend getting one to try to correct your problem, it won't help. I'm also do not see how Smart Tabs would affect the porpoising to any significant degree, although adjustable trim tabs might.
Store more weight in the bow to increase the polar moment of the hull which will slow the oscillation down and the added weight will stop some porpoising on its own. Also, use a GPS to check the speed with your trim. You may find that the speed you think you are picking up is in the speedometer pickup but not real.

 

[cribber]

Re: Hydrofoil stabilizer or not?

If porpoising is a problem then trim tabs are the way to go.

 

[QC]

Re: Hydrofoil stabilizer or not?

I'm also do not see how Smart Tabs would affect the porpoising to any significant degree, although adjustable trim tabs might.

Stop trying to guess on that one. Both examples have a significant impact (positive) on porpoising.

Store more weight in the bow to increase the polar moment of the hull which will slow the oscillation down and the added weight will stop some porpoising on its own. Also, use a GPS to check the speed with your trim. You may find that the speed you think you are picking up is in the speedometer pickup but not real.

Good suggestions. ALWAYS try weight shift first. I insist on trim tabs on my boats, but weight balance is important to the efficiency of the whole setup and will have an impact on porpoising. See steelespike's comments above ^^^^^.

My sig used to be "Friends Don't Let Friends Use Hydrofoils" I have loosened some due to steelespike and a few others. (LT now too) I think I like them on very small aluminum and similar with less than 25 bhp, and that is a major step for me . . .

 

[bluka43]

Re: Hydrofoil stabilizer or not?

Steelespike, You may have hit on something, or at least got me to thinking. When I purchased the boat 6 years ago, the motor was mounted on the transom about 2" higher than it is now. At first I wondered why, because it didn't look normal, but I never bothered asking the previous owner. After using the boat for a few weeks, I noticed the prop would cavitate a bunch on somewhat tight turns. I do remember the tach running 5500 RPM when running full open and trimmed, however, I can't remember if the boat porpoised at that time. After studying the situation and noticing the cavitation plate above the bottom of the transom, I decided to lower the motor to where the mounts sat on the transom, not 2" above. This also put the cavitation plate even or very near even with the bottom of the transom. It also stopped the prop from cavitating in tight turns. I just wonder if I need to raise the motor back up, perhaps to a happy medium, say 1"? Would 1" make that much difference? I certainly have no problem with hole shot, because it gets up and planes pretty quick. As for adding or shifting weight to the bow. I have as much as I need to store up there while underway.

 

[5150abf]

Re: Hydrofoil stabilizer or not?

A properly set up boat will blow out in tight turns, that is just how it is, all you need to do is bump the trim down a tad when turning, my boat is set up like this and after the first couple times it is just natural to tap the trim when turning.

Up and out baby, raising the engine can get you huge inprovements in speed and it is free!

 

[Joshua Nichols]

Re: Hydrofoil stabilizer or not?

NOT....... I had it on a ol jon boat and it was the only one I could tell a difference with... The boat I have now came with one and I am thinking of removing it..... I can feel the drag.. Not sure why he put on this boat with a I/O.. People do weird stuff

 

[joe009]

Re: Hydrofoil stabilizer or not?

i would try it.is your motor a 4 stroke? i put one on my f150 and it helped out a lot.

 

[bluka43]

Re: Hydrofoil stabilizer or not?

The motor is a 2-stroke. Due to the number of negative comments and experiences from other forum members, and because my boat gets up on plane quickly enough.......I have opted to NOT install a hydrofoil trim on the motor. I now think that it would be a waste of time and $$$. I thank you all for your comments and suggestions.
I will more than likely raise the motor back to it's original setting on the transom as when I purchased it. As soon as this is done (probably over the weekend), I will put it in the water and give it a try. If it's ok with everyone here, I would like to post the results, It may help someone else with a similar problem. Since I'm a newbie to this great forum, should I post the results on this thread, or post a new thread with a new title?
Thanks

 

[1979checkmate]

Re: Hydrofoil stabilizer or not?

try some different props too

 

[steelespike]

Re: Hydrofoil stabilizer or not?

Yes by all means let us know what happens.In this thread is fine. A prop change could sove the venting in corners.A prop with a little more cup perhaps.Or a 4 blade will likely solve any venting while improving hole shot,ability to stay on plane with less throttle,handle better on plane and at the dock and dampen porpoising.
Sometimes reduces top end slightly.