WHY WHY WHY

[checkmate243]

carb or tank?

First things first. Is it the carbs or gas tank? To determine is not the tank buy or borrow a portable tank and run it on that. If the problem goes away it’s the tank. If not it’s the carbs. Sound like you need to clean the carbs. Good luck.

 

[Needafunboat]

Holy cow - 32:1, do these things really need that much oil? My little 200cc KTM enduro (makes 41hp and is a very mellow, torquey engine) runs just fine on 50:1 full synth. Some guys run 100:1 amsoil, but that's scary.

Sleds and my seadoos inject VERY little oil. I notice my '87 150 merc seems to use alot of oil, based my estimate of all of about 2 tanks of gas I've run though it.

I'd agree that smoke is better than a rebuild, but too much oil gums stuff on on anything with a powervalve - rotax or a bike. I still don't know much about these mercs. My guess is if it ran good on 32:1 on 1990's oil, it will run 40 or 50:1 on a good semi synth. I do love the that smell though!

 

[merc245]

32 /1 ratio is called for when you plan on running your rpms upto at least 7500 i.e mercury racing products 2.5's 245/260/280s or a hotrodded motor.
Back in the day I'd would burn atleast 30gals of mercs premium plus a season.