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25 merc 4 stroke efi cut in/out under load

E

Effer

New member
re: model #1-A25203f K, serial #0R497394

I bought it new few years back and had been running fine since until the other day. It started and ran fine and then under 1/2 throttle bogged down and then started cutting in and out until I backed off the throttle, then smoothed out but would cut in/out with more throttle. limped it back home and thought it might be injector related so ran some injector cleaner thru it. Ran fine under high idle for 1/2 hour or more but when in gear under load would start sputtering. I cleaned the fuel filter screen in the small canister and also the pickup screen in the tank. Some debris but nothing that was stopping fuel flow.
Any thoughts? Thnx in advance for any help.

Effer
 
New here......did you ever diagnose your issue?

I am having a very similar problem on the same motor. Mine doesn't "cut out" but has lost almost all power when throttling up out of idle. Runs fine, just won't push more than slightly above idle. Fine in the driveway, just exhibits under load. I have changed both fuel pumps, cleaned VST, changed plugs, thermostat, fuel line, and had injectors cleaned/checked.
 
Duck-Hunter said:
New here......did you ever diagnose your issue?

I am having a very similar problem on the same motor. Mine doesn't "cut out" but has lost almost all power when throttling up out of idle. Runs fine, just won't push more than slightly above idle. Fine in the driveway, just exhibits under load. I have changed both fuel pumps, cleaned VST, changed plugs, thermostat, fuel line, and had injectors cleaned/checked.
Click to expand...

Nope. Mines currently at a Merc dealer waiting diagnosis. Sounds your problem is different. Good luck.
 
FWIW turned out to be fouled plugs. Prior to bringing it to the dealer I pulled the top plug and it looked fine. Didn't bother checking the lower 2 as they were harder to reach but apparently they were wet and fouled. Asked the dealer what would cause the 2 plugs to foul at the same time and they said that if the vent on the tank is closed while sitting the expansion of the gas in the tank would push thru the fuel system and reach the plugs. Hard to believe that but it runs fine now after replacing all the plugs. With labor, parts, and lake test was just shy of $3bills. Silly me for not checking all the plugs.
 
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