I have a 60hp mercury motor on a 15' boat. With ear muffs on the motor runs and ideals fine, but in the water it has no power and won't reve up. I took it to the Marine shop and $371 dollars later it runs the same. Took it back to the shop and he tells me he put it in the test tank and it was running at 5500RPMs and he can't find anything wrong. Went back to the water and at WOT maybe 5-6 knots. Now what? I want to go salmon fishing but at this rate i can't. Need help. Thanks