Hydrofoils...

[shauncooper]

Hi all - running twin 60hp Yamaha high thrust 4-strokes on a 21' Buttcat...

A couple of people of suggested I add hydrofoils to increase holeshot which I have mentioned is a little sluggish in the surf.

Any thoughts on hydrofoils - good/bad (I realise there is a lot to take into consideration such as weights in the boat, boat setup, etc).

If good, which brands or designs work best?

Thanks.

 

[QuQ]

Hydrofoils can improve hole shot, but at the cost of slightly reduced top end speed and increased fuel consumption due to the extra drag.

Have you considered playing around with props? What props are currently fitted and what revs do you get up to when flat out with a "normal" load?

I ran the F70's on a Seacat 565 which is a heavy boat and got better performace when I switched to a stainless prop which didn't flex as much when the motor is under load.

You could also look at switching from a 3 blade to 4 blade for more hole shot, this has worked well on a F200 (4 cyl) that I currently run.

 

[shauncooper]

Funny you should mention the props. I have just purchased a set of 4-blade S/S props in 13 pitch. My boat is currently having deck re-done so havent had a chance to try them out yet. There may be times though where I need to use my existing aluminium props (which I think are 15 pitch) due to potentially rocky locations for launching.

I'm not too worried about the top-speed as seldom run WOT anyway and I don't think there should be too much impact on the fuel consumption if the motors are trimmed right, if I am correct.

Is one brand or type better than the other?

 

[willem wikkel spies]

unfortunately our boating market is crap.
not all available props are imported.

playing around with props first is the recommended way of getting it right.

getting props to make such tests is your problem.
hydrofoils should assist in getting the arse up quicker.

my comment does not leave you with a answer unfortunately.

 

[QuQ]

Not too sure on the hydrofoil brands, but I would try those new props before buying hydrofoils. If your aluminium props are 15", you will see a big difference in hole shot with the 13" stainless props - I doubt you will need hydrofoils. Just make sure that your motors get to 6000 rpm or so to ensure that you are propped correctly (i.e. avoid labouring the motor). Also, most hub kits are now designed to "give" before your gearbox does when hitting rocks etc., so I wouldn't worry about ever fitting those alu props again.

From my personal experience and trialling various stainless options, the best stainless prop for the Yamaha F60/70 is the Turbo 1 / Stiletto 13.25 x 13" 3 blade.

 

[shauncooper]

Thanks for the replies. I hadnt answered your previous question on RPM, I wasn't getting close to the correct RPM for WOT with the current props, was running about 5200/5300 at WOT which is why I looked into some new props in the first place.

Also recently found that my deck was wet, so hoping with the new deck on (gone with light weight Nidacore) I should be running a good deal lighter as well which will help. Hopefully deck will be done by end of the week so can give it a test.

 

[QuQ]

With those revs, you can sell those aluminium props as they are no good to you. Your motors are labouring and will eventually begin to "make oil". The new props and the weight saving of sorting out the water issues will see much improved performace.

 

[Seadoc]

I agree with the above posters in that hydrofoils won't solve inherent setup faults.
They do work very well to increase holshot and to give a more horizontal attitude when planing ( they lift the stern)
I had a New Zealand made Permatrim on a 4.9m aluminum boat with a Yamaha F60. Top speed with or without the foil was about 32 knots, I could not notice any difference in fuel consumption. Made a big difference in the hull performance. The boat has now done about 650 hours, no problems with the transom or the ventilation plate. The Permatrim is made from aluminum and has quite a large surface area, hence the effectiveness. You can google them and have a look.