I recently bought a boat with a mid 1980's 150 hp Thunderbolt. I also a own a late 1960's 20 hp merc, which runs great and has never vin me problems.
The problem i'm having with the Thunderbolt is, when ever I take off with full throttle, it goes great for a couple of seconds then backs off. The engine still sounds great and does not sputter or miss. I'm only getting a top speed of 22-23 mph. I can definately sense it wants to do more.
Any help or theories would be greatly appreciated.

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Chris Grasman<br />Stayner, On<br />cgrasman@sympatico.ca