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I've been told by several sources that a hydrofoil can reduce your top end by 4-7 MPH.
I put one on my 20 HP Tohatsu to get on plane faster but I need the speed more than getting on plane.
Any of you guys know this to be true??
I'm thinking about taking it off to see, but was looking for other's experience.
I can recall having the same issue with my 40 hp Nissan on a 15 ft Alumacraft wide bodied jon. I loved how the boat would jump up on plane... but I actually had to drop the motor two more holes to offset the hydrofoil's tendency to load up the back end of the boat. In other words the back end of the boat was plowing a bit causing a loss of top end speed. Hard to believe what difference such a small adjustment made.
16ft alumacraft 40 hp Yamaha. Put one on and gained hole shot, lift and about 3-4 mph. Can’t see how it would hurt top end unless trimmed down to far. If no trim and tilt you might try tilting up one notch and see how it performs. Sometimes you just have to play with motor a little when you make a change. Do you know for sure you lost speed?
I actually meant to say that I also gained top end speed very similar to what cray describes above... a total improvement over the performance prior to installing hydrofoil.Quote:
Originally Posted by Cray
I had one on my 25 horse 16’ stick boat and it was a dog without it. I’ve heard of the loss of top end with bigger motors but not with the smaller ones. The hole shot has always been such an advantage that I never gave the loss of speed a consideration.
I've had one on every boat I've ever owned but my current one (only because there isn't a need for it). I've personally never seen a drop in speed. As others have said, It was a huge holeshot/up on plane improvement and the main reason for the installation. It also eliminates porposing which robs you of top end speed. I've had it on a 25hp 2 stroke, a 4 cylinder I/O, and a 40hp 4 stroke. I've only ever utilized one brand (Doil Fin) so I cannot comment on other brands, their design, or their operation increases or shortfalls.
Lots of variables but I doubt you will see 4-7 mph decrease on a 20hp. Assuming you don't have power trim, your motor could be tucked in too far. One of the main reasons for top end loss is mainly for rigs where the foil is under water when planed out which creates drag. I've had foils on 2 boats (both had power trim) and haven't seen any speed reduction. You could check your speed with and without to see.Quote:
Originally Posted by SeaRay
Dropped a couple mph when installed on mine
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I pulled mine off. Will check it ans see if it changes.
I’ve had a Stingray foil on my last two boats and lost no top end speed. It helped the hole shot and decreased proposing issues on plane. Some folks are dead set against them saying that they mask an underlying issue with how your boat is set up. I look at them as a relatively cheap way to improve performance on many boats without putting a ton of work into them. I plan on putting one on my current boat when I get around to it.
I believe some that loose top end is there motor needs to be raised up one or two holes once on plane the foil should not be in the water only skimming over the top or higher..
Well I tried it without the foil and I could get it ti 26 MPH about a 1.5-2 MPH gain but it starts to porpoise once it tops out. I tried numerous trim setting but never found any that reached 26 without the porpoise.
I need a CMC tilt/trim.....sigh, more $$$$.
Check out Bob’s Machine Shop for a trim and tilt. No bad reviews I could ever find and had one now for 4 yrs on a 25 yamaha. Bob's Clamp-on motor tilt and trim (Action Series) 40HP
Had one on a '14 semi-v with a 25hp Johnson. Boat was rated for 25, but that motor was a little heavy for the boat. Without a foil it porpoised so badly that you couldn't go faster than 25. With a foil, on plane within seconds, no porpoising at all, 32mph top speed. If this motor had PTT, I maybe could've gone without the foil.
My current boat has one, I may take it off just to see what difference it makes.
I put a Stingray on my Mercury 115 2 Stroke last year. Hole shot much, much better and no loss on the top end.
It definitely is much more sensitive to tilt / trim adjustments however. Even the smallest changes show at the tach, on and off the rear pad, and sharp turns at cruising speeds. I have also noticed a small change in how the boat steers with the motor trimmed up at some ramps as I approach to load the boat on the trailer, not much but it is a little different. Boat seems to wander a little side to side as I slowly ease up toward the trailer. If the water there is deep enough, the lower down the foot is, the straighter she goes.
Not a deal breaker, just my observations.
Overall, still glad I installed it.
My Dad used to put them on His "Run-a-bout" boats and swore by them.
For those thinking about one, shop around, the price varies greatly!
Appreciate all the input. Thanks.
I did a little experimenting. Took the Stingray foil off of my 60hp Merc 2 stroke. It's on a 17' Tracker Deep V.
It is slower to plane without the foil. The bow rises higher and then levels out once on plane. Trim settings were much more sensitive. It took very little upward trim to start porpoising.
It's hard to explain, but the boat had more of a "loose" feeling without a foil. It seemed to roll more with the waves.
With the foil on, the boat rises up almost parallel with the water, and takes less time to plane. It takes a lot more upward trim to make it porpoise.
As for a difference in speed, there was none. 31mph with or without it.
Long story short, I'm putting the foil back on. It certainly seems to help.