Re: hydrofoil that attaches to sterndrive
Yes torcano, I have direct experience with hydrofoils that attach to the cavitation plate. Mine was a Stingray brand and was an immense help on my 1980 Grew 18' with the Merc 470. It's been on for ages and I won't be taking it off.
It is a fix for problems and not a cure for the worlds ills. It does not increase mileage except that you can get on plane faster so you burn less fuel. It is absolutely the cheapest way to get your boat to plane faster and as a result helps get skiers and boarders up quicker. It made my steering heavier. Yes, they really do work and are cheap to buy and install, and easy to take off if the side affects are more negative than the benefits. Helm adjustable trim tabs are better and have added benefits but cost more. With them on your boat you should be fine.
This subject is polarizing. Personally, if I was going to think about Smart Tabs if would skip that step and just put on a set from Bennett. However, I am glad I put on my hydrofoil. My enjoyment of watersports went up greatly when it was installed. Now I've got my inboard and rarely take the I/O out.