Mercruiser 4.3 Dying Problem

larryarnaud

Recruit
Joined
Jan 8, 2022
Messages
5
I was out salmon fishing and a wave came high and water went into the gas vent hole even though I have a one way valve on it. The motor stalled. After about fifteen seconds, it fires back up. It runs fine for about five miles going in, then it sputters, backfires, sputters, dies. It did not start again even with starting fluid. I had the boat towed back to the ramp. It did not start at the ramp. After getting home about 1.5 hours later, I tried it and it fired right up like it hadn’t ever missed a beat.

I moved the gas vent hole to a better location, changed the gas filter, looked at a couple of spark plugs, and everything seemed fine. I started it up a few times within the next couple of weeks, and everything was great.

I took the boat out on a lake and pulled water tubers around for about five hours, idling, throttling up and down, and the boat didn’t miss a beat. It ran perfectly. I then took it out crabbing. I ran out about 13 miles, dropped the pots and it ran perfectly again. The next day the water was snotty when I needed to pick up the pots. On the way out, the boat sputtered a couple of times at about eight miles then ran fine. Picked up the pots and was heading back in. At about nine miles left to the harbor, the boat sputters, backfires, stalls. I start it, it sputters, backfires, dies. I tried starting fluid, no start. I placed a spark plug testing light from the coil to the distributor and the light flashes while cranking. I know there was spark from the distributor to a spark plug wire while trying to test it because it shocked me real good. It was still dead. I got towed in. The crabs were good.

On the next day on the driveway, I try it and it fires right up. I take it to a mechanic and he states he is sure it is the coil after looking at a spark tester. He states that the spark isn’t strong and wasn’t continuous. I ordered a new OEM coil and he has a machine to compare the old coil and the new one. I will change the plugs, distributor cap, wires and ignition sensor.

I’m posting here to see if there is something else someone can spot that might be the problem. Having to be towed in twice is not pleasant.
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
Throw about a litre of metholated spirit in the tank. It'll pick up any water and carry it though the fuel system.

And stop using starter fluid. That sh*t is meant for diesels, not petrol engines. Unless you want holes blown in your pistons...

Chris......
 

larryarnaud

Recruit
Joined
Jan 8, 2022
Messages
5
Throw about a litre of metholated spirit in the tank. It'll pick up any water and carry it though the fuel system.

And stop using starter fluid. That sh*t is meant for diesels, not petrol engines. Unless you want holes blown in your pistons...

Chris......

Throw about a litre of metholated spirit in the tank. It'll pick up any water and carry it though the fuel system.

And stop using starter fluid. That sh*t is meant for diesels, not petrol engines. Unless you want holes blown in your pistons...

Chris......
Thank you for they reply. I'll try the spirit.
 

larryarnaud

Recruit
Joined
Jan 8, 2022
Messages
5
Sounds like a little wave action and you're pulling up water in the tank.
My boat is a Blue Water, too. The puzzling part is that on the second time it happened, I am sure no water went into the tank through the vent hose. It is also puzzling that it starts once back on the driveway.
 

QBhoy

Fleet Admiral
Joined
Mar 10, 2016
Messages
8,348
sounds like bad fuel...try running her off a remote tank of fuel from a can. But I would suggest that once crap fuel has made its way to the engine (especially a carb)...most times the carb needs to come off.
 

larryarnaud

Recruit
Joined
Jan 8, 2022
Messages
5
Thanks everyone for your input. The boat was starting and running. It is hard to figure out the problem when it starts runs fine. Nevertheless, I changed the coil, ignition sensor and plugs. It sounds even better now. I'll see how it goes when I'm on the water. Halibut are starting to show up in the Bay.

I just have a rattle that is coming somewhere around the bell housing. It only is there during idle. It goes away when throttling it, even just pushing a little on the throttle. I'll post it on another thread.
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
27,468
I just have a rattle that is coming somewhere around the bell housing. It only is there during idle. It goes away when throttling it, even just pushing a little on the throttle. I'll post it on another thread.
Exhaust shutters, completely normal.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
Joined
Jul 23, 2011
Messages
50,587
inspect the exhaust shutters. if the rubber bits are missing, your motor suffered an overheat
 
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