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1980 Mercruiser898,305 cu in,198hp rpm's slow, then motor dies.

S

smb1

New member
Loses rpm and eventually dies after about 20 minutes. Engine just rebuilt. Could it be the fuel pump, fuel filter, condenser coil? Other?
 
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Add:
fuel line fron tank
anti-syphon at tank
clogged tank vent line
Could be a lot of things, what have you tried to narrow it down?
 
I have not physically started testing items. Was thinking aloud to get a prioitized starting point. Thanks for your post. Where should I start?
 
I have always thought that spark is usually on or off (not intermittent) and that fuel was more likely intermittent. Was thinking of fuel filter and fuel pump. Is there a second fuel filter near gas tank?
 
Most have a water sep just before the fuel pump. The anti-syphon valve could be clogging, its the very first fitting at the tank.
 
Find out at the moment it happens what it is spark, pull a spark plug wire off and place a spare in the end and crank the motor and hold the plug to the block.

Got spark then it's fuel.

Then go after the problem, with your list.

We can go after the problem all of us together giving tips to you.

Understand ?
 
Installed new water/fuel separator (no water) & ignition coil. There is no anti-siphon valve at gas tank. Pulled out in line fuel filter at carb and it was perfectly clean. There is no gas in the fuel pump overflow chamber which suggests the pump is good? Checked all electrical connections & they are tight. With ears, boat runs well. Need to put it in water for load test - maybe this weekend. Condenser next.
 
I'll wait till you find out what is missing.

Oh was there a 90 degree fitting on the tank? Thats the anti-syphin valve, you unscrew it and up comes the fuel pickup tube.

The vent clear ?
 
There was no 90 degree fitting. Gas line connected to gas tank nipple. I plan to recheck this as now I'm having second thoughts.
 
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you say nipple i say fitting, smells like a pig and walks like a pig you can put lipstick on that pig call it anything you want it's still a pig.
 
The fuel pump overflow nipple is prone to clog w/hard varnish like earwax. It prevents fuel from a leaking diaphragm getting into the plastic line.
 
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