hydro-foil

I found an old stingray hydro foil that I installed on a 1994 Evinrude 90 GT to get me on plane quicker..Worked great. Just fooling around last night I installed it on my 1969- 18 hp Evinrude .My question is will this "foil" have any adverse effects on my little 18 hp motor ? like overheating . I think I read somewhere that foils change the cavatations [sp] and could cause overheating? I would hate to burn up a good motors. if anyone has a pro or con opinion ,I would appreciate a heads-up...
thanks for your time
Ken

I do not see it causing overheating - but keep an eye on the "pee" flow from the motor - if it is peeing it is getting water to the engine

If no pee - then overheating

I have one on my 20hp. Seems to make a difference

Difference in overheating... or performance? I had one on my 18hp Evinrude as well, but I took it off when I repainted the motor and just haven't put it back on. Some I know it gets you on plane quicker, but will it increase top end speed?

A 1969 does not have a tell tail. Water should spit from the exhaust post just above the water line.