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Older Merc 1150 motor issues

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steven133080

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Hi guys, I will be the first to admit that I am no master mechanic, but last year we put another motor on our boat. Its an old 1970 something Merc 1150 (115 hp) motor. Last summer it ran fine, and towards the end of August we ran the tank nearly dry, but not completely. Like a dummy, a couple weeks ago when I took it out for the first time this year( Waay too busy of a summer), I just put some new gas and oil in the tank , and took it out. I had started it a couple times in the driveway this spring with the anticipation of going out, but it didnt happen until recently. Anyways, motor starts up, idles good, put it in gear and it works fine up to about 7-8 mph. Anything past that on the throttle it seems to choke out the engine, and it dies. Any advice on what it could be without taking it in to a shop? I would think maybe dirty carbs, but I would think it would have a hard time starting and idling if that was the case. It will go all day long at 7-8 mph, but once you go past that on the throttle, it dies. Any ideas on what it may be or advice? Im not even sure if I can get parts for that old of a motor anymore can I?

Thanks for any ideas you guys may have.
 
Did you use a fuel preservative last year when you filled the tank? Old gas in the carbs turned to crap. Try this procedure before rebuilding the carbs. Disconnect the fuel line to the engine and run the engine to empty the carbs. Reconnect the fuel line to the engine. Keep the engine in the down position. Disconnect the tank end of the line and stick it into a can of SeaFoam. Pump the solution into the carbs w/the squeeze primer until it is hard. Pour the balance of the SeaFoam into the gas tank. Reconnect the fuel line. Let the SeaFoam soak for 24 hours...48 hours is better. Start it and run it at 1500 RPM in the drive w/muffs or take it to a lake and run the snot out of it. It will smoke heavily but it is okay. Always use Stabil or equal w/every fillup of the fuel tank because you never know when the boat will sit for a long time. Gas starts to break down after 30 days and eventually turns to a varnish like sludge.
 
Thanks for your advice

We never added anything to stabilize the fuel after last years trip. We kept thinking we would take it out again before the season was over, but it never happened. I know when it was put away, there was less than 1 gallon left in the tank, and I can only imagine how that fuel could break down. The boat is stored with the cover on it, and days ranging from zero degrees, up to 105 degrees in between. I will give the Sea Foam a try.
 
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