hydrofoils question

[vr4rhoads]

Basically just wondering what everyones exp are with them. Are they good to go? Will a 70 hp yamaha withstand the added hydrofoil? I live in Corpus christi so we run shallow in the bay all the time. its for my 16 ft predator

[boscoe99]

This is a widely debated topic.

Some folks swear by them, some folks swear against them and some folks don't have an opinion. What is funny to me is that those that did not have success with their use of a foil will swear that they can be of no use to anyone.

I used one on first my 175 EFI Mercury and then installed it on my F200 Yam. It worked well for me. Got the boat on plane easier and let it stay on plane at a slower speed. Also helped to prevent ventilation somewhat when making hard turns with the motor trimmed up.

I see no reason why it would not work on a Yam F70.

In my case I clamped it on to see how it would work, before drilling any holes. It worked so well clamped on that I just left it that way.

Here is a photo or two of it on my Yam. I bought the stainless steel version but if I had to do it over again I would go with aluminum.

[vr4rhoads]

hmmmm might just get trim tabs

[vr4rhoads]

This is a widely debated topic.

Some folks swear by them, some folks swear against them and some folks don't have an opinion. What is funny to me is that those that did not have success with their use of a foil will swear that they can be of no use to anyone.

I used one on first my 175 EFI Mercury and then installed it on my F200 Yam. It worked well for me. Got the boat on plane easier and let it stay on plane at a slower speed. Also helped to prevent ventilation somewhat when making hard turns with the motor trimmed up.

I see no reason why it would not work on a Yam F70.

In my case I clamped it on to see how it would work, before drilling any holes. It worked so well clamped on that I just left it that way.

Here is a photo or two of it on my Yam. I bought the stainless steel version but if I had to do it over again I would go with aluminum.

Hmmm interesting, basically I have a 16 ft predator, and it tends to slide when it turns (design of the boat from what I understand not motor related) so I had heard that a cav plate would help tame the slide and help with my hole shot which is good in the luguna madre bay

[ausnoelm]

what are you trying to achieve? No use just fitting a foil "because"

[vr4rhoads]

wanting to stabilize my turning and get on a plane faster, like I said I fish the bay here and its very shallow.

anyone have exp with xs smart tabs?

[boscoe99]

You asked about hydrofoils and I responded accordingly.

Trim tabs are altogether different.

My boat had them as well and I would not have a boat without them. Bennett brand is the best IMO.

With trim tabs deployed and the hydrofoil installed when I powered the motor up the whole boat would just rise up. No bow lift at all. One second it was sitting in the water and the next second it was on plane.

Not sure what you can do about the boat sliding.

[vr4rhoads]

You asked about hydrofoils and I responded accordingly.

Trim tabs are altogether different.

My boat had them as well and I would not have a boat without them. Bennett brand is the best IMO.

With trim tabs deployed and the hydrofoil installed when I powered the motor up the whole boat would just rise up. No bow lift at all. One second it was sitting in the water and the next second it was on plane.

Not sure what you can do about the boat sliding.

hmmm well thanks for the response, gives me some more to think about, ill take a gander at those tabs you recommended, didnt mean to sound rude or ungrateful. Was not my intention, and I am thankful for advice and knowledge.

[CatCam]

I have a F90 on an 18' Lowe Roughneck Aluminum boat. When I first got the boat I had a lot of bow rise before the boat would plane and porpoising if I didn't continuously trim.
Installed a SE Sport 300 WAYYYY back in 2005 -- Night and Day difference.
Hole shot is much improved, handling is much improved and top speed was not impacted.

[ausnoelm]

If there is any difference in top speed after fitting a foil, you have a motor height problem, the foil should be out of the water when on the plane, most fits foils in the hope of fixing a setup problem, when in fact, it is just putting a band aid on a gaping wound, make sure you know what you want before you start, don't know how the depth of the water you operate in has much to do with fitting a foil.

[DennisG01]

Foils are hit or miss. It all depends on the engine/boat/load configuration. In some cases they help, in some cases they actually hurt performance. Clamping it on for a trial period is a great idea. As far as whether your engine can "handle" it - no worries - it can be put on any engine.

Bennett trim tabs are absolutely wonderful. But for your boat, it might be overkill (at least from a money standpoint). The SmartTabs that you referenced, however, are fantastic for smaller boats! You will notice a HUGE increase in hole shot - also keeping the bow planted during some choppy water. I would absolutely do the Smart Tabs before a foil - they will bring a much bigger smile to your face. Super easy to install - can be done in less than an hour. One word of caution - they used to recommend using 3M5200 (not sure if they still do). Don't use that. 5200 is like super glue and this is the wrong application for that.

EDIT: Also, hydraulic trim tabs can be a little daunting to install, depending on your skill set.

[vr4rhoads]

If there is any difference in top speed after fitting a foil, you have a motor height problem, the foil should be out of the water when on the plane, most fits foils in the hope of fixing a setup problem, when in fact, it is just putting a band aid on a gaping wound, make sure you know what you want before you start, don't know how the depth of the water you operate in has much to do with fitting a foil.

So ideally what height would you want your motor, I actually am planning to pull my motor to put in a much large plate for my transom/motor mount so I can adjust accordingly while im at it

[ausnoelm]

The cav/anti ventilation plate shuuld be just skimming, or just above the water.

[almetelo]

On my case (a KL 16 with a F100) the hydrofoil helped a lot since the motor is to heavy for the hull (the hull should have a 65HP max) and while planing and using the F4 kicker that I rarely use the bow was always up and down even with motor all trimmed down so hydrofoil fixed that and I have a better planing now with or without kicker (No diference at all at WOT)

Follow the Boscoe suggestion (thats what I would do)

[99yam40]

Not sure what you can do about the boat sliding.

Flat bottom or semi V boats tend to slide more than vees.
Need something on the boat to grab the water. I do not think there is anything you can do on motor that will help.

But some of the foils have adjustable things that stick down off of the bottom to help counter act prop torque like the trim tab zincs