Re: Hydrofoil
I haven't jumped in on one of these threads in a long time.
Most of those that hate foils have no clue as to how they are supposed to work, what they actually can do, or how to set one up correctly. This doesn't mean every boat will benefit by using one and an I/O is less likely to benefit without a trade off in some areas.
To be used correctly the foil should not be in the water at speed, this is where the possible handling issues come from, its also the reason it can be difficult to set it up on an I/O.
What a foil does. It allows you to raise the motor up on the transom so there is less gearcase drag, this may result in a higher top speed, better mileage and less bow rise due to less leverage. The foil just helps to prevent ventilation by placing a barrier between the prop and surface so air can't be sucked down.
If you have the foil dragging in the water it may help with a couple of things, but may also cause the handling problems many people report. The vast majority of people just bolt one on and head to the water and expect an improvement in every aspect of performance, well it doesn't work that way. If one will help and that's a big "if", you won't know until you do all the set up work and possibly change props.
Trim tabs and foils do totally separate things, and while there ?may? be some similar benefits, they go about getting the job done in a different manner.