I'm having a problem with the 5.7, carburetored Mercruiser engine in my boat. I was winterizing the boat today, warmed the engine for about 20 minutes (ran fine) and changed the oil and filter. When I refired the engine, it kept stalling out. It starts normal, runs for about 10-15 seconds then cuts off. It will restart fine and do the same thing. I let the engine cool, while I changed the lower unit oil, to see if it was temp. related, no change. I'm pretty sure it's losing spark, here's what I have observed: No abnormal smoke from exhaust, engine speeds up a couple hundred rpm for a couple seconds just before it stalls, carb has gas in it after it stalls and pumping throttle as it's cutting out makes no difference. Engine runs fine and will rev up until it cuts out. It was getting dark (and cold) so I couldn't check much except to make sure I didn't knock something lose. I plan on working on it tomorrow so any advice anyone has would be helpful. TIA

Andrew

You have to determine whether it is spark or fuel related. After it stalls out, with the engine off and not cranking, have someone pump the throttle while you look into the carb to see if fuel is being squirted in from the accelerator pump. If there is fuel present, then most likely the problem is spark related.

Gas sqiurts out of the accel pump after the engine stalls so I am pretty sure I'm losing spark. I just don't have a spark tester at home to be 100% sure that is the problem.

Sounds like it is running out of fuel. An engine always speeds up as fuel runs out. This is because the a/f mix begins to lean. Did you change the fuel sepertor and fill with fuel before reinstall? Maybe pinched a fuel line when changing the oil? Also, if for some reason you got water into the carb, the water would be displacing the fuel in the bowl and not allowing the float to drop and let in more fuel.

BT

I had a similar problem...one tiny wire in the wiring harness had chafed through. The engines vibrations would cause it to short out on the block. It would restart just fine until the harness shifted again. One day, a friend and I both heard the arc...can you say fire hazard?..After lots of fresh air, and some close observation...and a piece of electrical tape, problem solved.

The shift interrupt located on the stbd side of the engine, assuming it's an alpha, is probably shot. I've seen it before, especially during winterizing, for it is a clumsy task. Possible you knocked into it or something.

Mercruiserparts.com has the whole new shifter bracket with a revised cut out micro switch. also has the spring loaded assist built in. $84 to save you guys alot of headaches. Original switches are not availiable Also if not done yet, put a new ss shift spool in the lower unit. the old brass ones wear creating excessive play. My 2 cents BBB

Might be the carb flooding.
If it sat winterized for a period of time, could be spunk in the needle & seat.

Your winterizing your boat already? where do you live?

Racer,

this thread was started back on 11-13-04! Hence he was winterizing!

Big block billy was just suggesting a new part for this guy.