merc 4.3L runs for 10 seconds then stalls

[fatbouy02748]

Hello, I have a 1998 Larson SEI-186, with a mercrusier 4.3L I/O. My problem is, boat was winterized in oct 2001 with 1/2 a tank of fuel. in June I burnt out the alternator trying to lift the sterndive with a car battery jumped to the dead battery in the boat. alternator caught on fire. after replacing it I took the boat out for a spin (with only the old fuel in it). the boat appeared to run fine for about an hour at both idle and up to 3500 RPM. on my way back the engine stalled. I could start it but it would never run for more that 10 seconds and never above idle speed. came home filled the tank with fresh gas and the next day she ran for about 1/2 an hour. now it is back to the same problem. will run at idle for about 20 seconds, or at 3000 rpm for about 3 seconds. Anyone have any ideas?<br /><br />Thanks Ed

 

[Trevor]

Re: merc 4.3L runs for 10 seconds then stalls

First check all filters for water.<br />if no water is present then proceed to see if fuel pump is moving enough fuel to keep carb full.

 

[andrewsilver]

Re: merc 4.3L runs for 10 seconds then stalls

Unfortunately I can't help - I have the same problem with my 1990 3.0L Mercruiser Alpha One.<br /><br />Mine is also backfiring when I do manage to get it up to 3000rpm for a few seconds. then it backfires and dies.<br /><br />I was told I might have an air leak in the carb, and that I should tighten down all the screws. I did, but no improvement.<br /><br />Any ideas greatly appreciated. thx,<br />Andrew

 

[flashback]

Re: merc 4.3L runs for 10 seconds then stalls

first thing I would do is to change the fuel filter, if that did't work I guess the next step would be the fuel pump.. back firing and dieing is generally a sign of fuel starvation...

 

[fatbouy02748]

Re: merc 4.3L runs for 10 seconds then stalls

Thanks for the thoughts. I already replaced the filter and there appeared to be some clam looking like substance in it. my buddy told me thats what water and fuel mixed together looks like. when I disconnected the fuel line after the pump and tried to start the engine it ran for a few seconds with the fuel in the bowl and pumped gas into a bottle. does anyone know how much fuel should be pumped like in oz/sec or whatever the measuring units might be?<br /><br />Thanks for the reply

 

[johnkc]

Re: merc 4.3L runs for 10 seconds then stalls

hello , back by the oil filter {assuming you don't have a remote oil filter}there is an oil pressure switch wich passes current to the fuel pump when the engine has built up enough oil pressure.remove the two purple wires and jump these together, do this as a test only . if the engine runs longer than previously, then that indicates the switch is bad.or worse case, no oil pressure .good luck

 

[markhlewis]

Re: merc 4.3L runs for 10 seconds then stalls

This one is for "andrewsilver:...<br />I have the same motor/ same problem...How ever it cost me over $500.00 to have the heads replaced. if you start your motor up and pour water over the the valve cover, look and see if the valve cover has bubbles comming from the bolt area (which means an air leak). If so, then you need your top end replaced. I know I know, I thought different also. I tried to tighten the bolts, but to no avail it had to be done.<br />Mark