Mercury 25 HP, 1985

by Larry
(Effingham, IL)

I have a Mercury 25 HP motor with a 13 pitch Solas prop, (long shaft) on a 17 ft Lowe aluminum fishing boat. Prop tends to spin and lose bite with faster RPM’s. Suspecting a ventilation problem as the gap between the motor shaft and propeller appears to be a little wider than what I see on other boats. I should point out that I recently purchased this motor used. Any advice will be greatly appreciated.