2003 4.3 mercruiser hard to starta

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Mdeshaies

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Ok guys I am pulling what is left of my hair out about this issue. I have a 2003 searay with a carburated (mercarb) 4.3 liter GM engine in it. It has always been fussy starting hot it cold. It was laid up for2 seasons and yes the gas was treated before it was winterized. The boat only has 200 hours on it so it is still fairly new.
Here’s the issue. After waking it up from it’s long nap, the engine would not start. It cranks over well (new battery) but no go. Replaced the fuel / water separator with new one and the engine starts and runs normal on the trailer. Launch the boat and it will not start. Towed to dock and removed top of carb to inspect bowl and it looks good but what the heck I took carb off and cleaned it, replaced the float needle and set the float. Put carb back on boat and the engine started so I took the boat out for a good run. Ran fine. Returned to dock and no matter what I tried it would not restart. I have tried to start it and just get a sputter. Kill switch is on, fuel pump runs and has pumps adequate gas into a can when disconnected, accel pump squirts gas when throttle is pumped so there is gas in bowl

why does it run so well one minute and then not. Some thing in the ignition that is marginal? Not consistent

any my ideas would be welcomed
 

SkiGuy1980

Petty Officer 2nd Class
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Aug 10, 2017
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Had a similar issue with a '93 4.3 that would run fine then would give us fits trying to restart. In our case the gear on the distributor was chewed. Once that was replaced we had no issues with starting/idling/or restarting. One of the smarter engine guys here can point you in the right direction, but thought I'd share our perplexing problem... just in case.
 

achris

More fish than mountain goat
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May 19, 2004
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.... It was laid up for2 seasons and yes the gas was treated before it was winterized....

Doesn't matter how well it was treated, 2 year old fuel is rubbish, drain the tank, have it cleaned, drain all the fuel lines, pull the carb and clean it. That fuel is ROTTEN/foul/sour, get rid of it.....

You also need to determine if the lack of starting is a fuel issue, or an electrical issue (ie, no spark)... Get a timing light, hook it up to a convenient spark plug lead and see if you have spark....

Chris........
 
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Hey all, I've been reading a taking notes. I have a separate but similar situation. For two years, I never had an issue with start up except for when my lanyard was loose. I have since replaced the lanyard, but it's not a perfect match. My kill switch is a red button that pulls out from the wall with a lanyard keeping it expressed. Now, when I try to turn over the engine, I still get the safety tone to turn on my blowers. However, as the engine tries to turn over, there is an intermittent beeping, my gauges flop up and down, and it won't turn over. I'm assuming a short in the wire, but I would also love to find a prefect matched lanyard for 1999 5.7L Mercruiser. Thanks
 

QBhoy

Fleet Admiral
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Mar 10, 2016
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I think you either have bad fuel, a blockage or restriction, or perhaps your auto choke is bad.
 

achris

More fish than mountain goat
Joined
May 19, 2004
Messages
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Hey all, I've been reading a taking notes. I have a separate but similar situation. For two years, I never had an issue with start up except for when my lanyard was loose. I have since replaced the lanyard, but it's not a perfect match. My kill switch is a red button that pulls out from the wall with a lanyard keeping it expressed. Now, when I try to turn over the engine, I still get the safety tone to turn on my blowers. However, as the engine tries to turn over, there is an intermittent beeping, my gauges flop up and down, and it won't turn over. I'm assuming a short in the wire, but I would also love to find a prefect matched lanyard for 1999 5.7L Mercruiser. Thanks

Please don't hijack old threads. Start your own.

iboats mod team.
 
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