I have a 1981 Eldocraft bass boat with the same year model 150hp Mercury outboard. I just recently bought the boat, and had to wait while a complete overhaul was done on the engine. The mechanic said to run double the amount of oil for about the first 10 hours to make sure everything stays lubed, so I'm running 1qt to every 6 gallons, instead of one pint to ever 6. He said not to do it too long or it will foul the plugs. The motor was very hard to start at first but cranks right up with starting fluid, then is pretty good afterwards. When I get down on the throttle, it just cuts out, then picks back up, then cuts out and picks back up... Does anyone have any idea what could be wrong?? Is it the double oil that could do that?? Because when u spray starting fluid in there, it'll run good, then start to mess up again. Thank yall!!!

Double oil won't do that. My guess is that one or more cylinders is starved for fuel. Those cylinders are also not getting any lubrication. Starter fluid makes it run - but has no lubricant. Better to use premix in a spray bottle.

What does the mechanic say?

Does your engine have a regular choke, with plates, or a primer solenoid? If it's a primer, are you holding the key in for 5 to 8 seconds (key in run position) before turning it over to start (cold engine)?