Runs great on muffs, but not under pressure

[jhoelting]

I've got a late 70's model Mariner 80hp. I've had it to the shop several times because the motor dies when dropped into gear. It will run fine on muffs. I've replaced alot of the electrical system and the compression has been checked by more than one mechanic and is found to be ok. The lower carb doesn't seem to adjust, but my mechanic supposedly rebuilt them. I wonder if he really did?
Has anyone else had this problem of boat dying when put into gear? And what ended up being the result?

 

[76canaventure]

Re: Runs great on muffs, but not under pressure

Hi there, just a few thoughts.
In my experience, 80% of the time, what your describing is the carb's are out of adjustment. (Also in my experience, everything runs fine on muffs. I've seen motors with 3 dead cylinders sound great on muffs, they're pretty useless as far as tuning a motor goes.) You have a carb that won't adjust, that's not right, and could have not been freshly rebuilt (properly, anyway.) Rebuild your carbs, check your idle and initial carb adjustments (try 1 1/2 turns from seated) on the muffs, then pop it in the water for tuning. You will find that a proper shop manual will be an invaluable tool.
Good Luck!

 

[jhoelting]

Re: Runs great on muffs, but not under pressure

I hear you there with the carb adj. After pulling carbs and soaking them and repacking, I had unit in water I started with 1.75 from seat and worked my way forward and back 1/4 turn at a time. Both carbs seem to fluctuate with the adjustments but couldn't get any better results. The motor chuggs a bit and then dies. It doesn't fall right on its face, it does a little chugging. Is it possible that a clogged exhaust system is to blame? And if so, how is this remedied?

 

[billgabbert1]

Re: Runs great on muffs, but not under pressure

check your plug wires u might have one mixed up.