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Mercruiser 43L MPI 2003 engine wonbt start when cold

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butch91901

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My 4.3L MPI engine won't s

My 4.3L MPI engine won't start when it's cold but once it warms up it runs fine. When it won't turn over I smell a gas. It sounds like it isn't getting enough air. Last weekend I put a small space heater in the engine compartment for a little while to bring up the temp of the engine and it stared easier still not normal but easier.
 
Clean the flame arrestor on th

Clean the flame arrestor on the throttle body. Use brake cleaner sprayed from the inside out or spray heavily w/a degreaser and rinse from the inside out w/hot water. Blow dry w/compressed air. What do the spark plugs look like? Original plugs? Time for a change if they are not platinum; just clean them.
 
I did notice some black build

I did notice some black build up on the trottle body butterfly valve. The flame arrestor has no filter element I thought this was strange. The flame arrestor is just a covering with hole almost like a sink stainer. I can see right thru it. Is that right? I haven't changed the plugs since i got the boat so I will change them.
 
Flame arrestor usually has a m

Flame arrestor usually has a multilayer coarse screen about 1.5" high around the cover. The dirt you saw on the butterfly (BFV) valve is critical. Get a can of THROTTLE BODY (TB) cleaner and not carb cleaner. Hold the throttle open and liberally spray both sides of it and the bore of the TB. Wipe it clean w/white paper towels. Spray the shaft ends of the BFV and then lube the shaft ends w/a drop of light oil. Lube all the linkage pivot points on the TB you'll be surprized how much smoother the idle will be.
 
I would also dump a can of Sea

I would also dump a can of SeaFoam into the fuel tank; 1 can for each 10 gallons of gas for now and run the tank down to 1/4. Then add 1 can of SeaFoam to each tank fill up for PM. You'll never have a varnish/gum issue again.
 
Thanks for the info. My flame

Thanks for the info. My flame arrestor is only single layer coarse. Also what type of filter material do I stuff in those side orifices in the throttle body??
 
The "flame arrestor" d

The "flame arrestor" does not contain any filtering material. It's there only to prevent flame from coming out the air intake in case of backfiring. Prevents the boat from exploding gas fumes. There is no air filter on gas marine engines like you have on a car. The flame arrestor over time can collect enough oil vapor and stuff to start to suffocate the engine - that's the reason to keep it clean.
 
"If it wont start on its own a

"If it wont start on its own and you smell fuel, one of the sensors providing info to the ECU is going bad. Best to get a scanner tool and find out which sensor (or its connections) is out and fix it. Its probably riching up the whole fuel curve which is costing you a fair mount of fuel."
 
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