1989 mercury 150 oc138172 RPM surge PLEASE HELP!!

[Bluewatermerc150]

I have a 89 Merc 150 that has been giving me fuel and electrical issues since i purchased it about 4 months ago, i have replaced all six coils, trigger stator and starboard side power pack, also rebuilt the fuel pump and cleaned all three carbs and replaced all gaskets. the issue it is giving me now is, when i have a load on the motor it struggles to get above 3000 RPMs then occationally almost at random it will jump to 4000 RPMs allowing me to get it up on step, at one point while on plane the RPMs jumped to 5000 RPMs but then back to 4k and then to 5k surging back and fourth, could this be a timing advancement issue that can be adjusted? I'm lost and not sure where to start looking>> any help would be appreciated.

 

[Faztbullet]

Sounds like you still have carb problem or a switchbox acting up. Check spark on trailer in gear at rpm as sounds like bias circuit problem...

 

[Bluewatermerc150]

will do I'm taking it to the boat launch today with my tools, ill keep y'all posted. thanks for the reply

 

[Bluewatermerc150]

does anyone know of a shop near panama city that has a test tank? I'm over taking my boat into a shop and having them tell me it all checks out only to get it on the water and have it do the same thing..