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Old 26-05-2014, 00:38   #1
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Join Date: Feb 2012
Location: Ballard, WA
Boat: Hunter 326
Posts: 13
Angry Yanmar 2GM20F, hard to start, won't idle

Long story short, my always reliable engine became unreliable this weekend:

-Yanmar 2GM20F, in 2002 Hunter 326.
~600 hours
-recently serviced, with new mixing exhaust U pipe & valve adjustment
-ran perfectly for ~10 hours or so after service

Last Friday I headed out for a long weekend with friends. She ran great all day. Come Saturday morning, she just wouldn't want to keep running at low RPM or run for more than a few seconds. The starter battery was good at 13.4V and the engine would turn properly with the starter, but with 0-to-1/8th throttle, it would run *very* roughly for 2-3 seconds before cutting out with a heavy shudder. With ~1/5th throttle, she'd run rough for 4-5 seconds before coming to an abrupt and bumpy stop.

After a couple dozen tries, and an attempting at bleeding the fuel lines (and a few more rough starts), I was able to get the engine started. It would run extremely rough and want to poop out under 1/4 throttle, but when underway, and/or above 1/4 throttle, she would run perfectly and smooth as can be. We headed back home under cruising speed (and even WOT for a few moments) for the next few hours without any sign of engine trouble.

However, when I'd throttle back, she'd still run terribly rough and would cut out again - requiring ample goosing of the throttle, swearing and much luck to get fired up and back running smooth at a ~1/4 throttle.

Of course, once I cut the trip short by a day, motored home for 4-hours and got her back into her berth, she seemed to run perfectly fine at normal idle speeds and would start and stop again like there never was a problem to begin with.

I'm curious if any of you might have an idea as to what was causing this somewhat intermittent but very problematic behavior?
MrSteve007 is offline   Reply With Quote

2gm, 2gm20, yanmar

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