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Old 05-07-2010, 10:37   #1
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Yanmar 1gm10 Performance Problem

good day everyone im hoping that theres a yanmar guru out there that can assist me with this problem im having with my engine.
first off its a 2007 1gm10 not rebuilt new unit. engine has been running excellent cruising along at 3200rpm never missing a beat. but in the last few months ive noticed that the engine bogs right down to say around 2500 -2800 rpm and this was usually after a night out on anchor. i was thinking that perhaps my alternator was drawing lots of power trying to recharge my batteries but for a test i removed the alternator belt and power harness and cruised back from this weekends outing at 28-2900 rpm. so i guess this rules out electrical draw im going to change the primary and secondary filters today but is there anything else i should be checking here. ive heard exhaust elbows getting clogged up but is this realistic on a new engine with only approx 250 hours?
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Old 05-07-2010, 13:22   #2
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ok after further investigation and changing the secondary filter (had to order another primary) the engine still runs the same. but tied to the dock if i put it in forward and throttle up it will rev to approx 2600 but if put it in reverse it will rev right up to 3400 now that makes me think that the engine is working ok is it possible that ive damaged my prop i changed to a campbell sailor 3blade last year and since the change ive only been able to max rev my engine to 3200 in forward. any thoughts?
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Old 06-07-2010, 10:26   #3
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wow 48 views and not one opinion come on guys someone has to have an idea here thanks
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Old 06-07-2010, 10:38   #4
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Are you sure your prop is clean? My 3JH3CE will not turn more than 3000-3200 if the prop is dirty. Are you saying that sometimes it turns up normal RPM?
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Old 06-07-2010, 10:43   #5
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just had a diver about a month ago clean the bottom he did mention that im due for bottom paint though. when i left last weekend the boat ran pretty consistent at 3200 with the occasional drop to about 3000 which i assumed was the alternator kicking in charging batteries. but when i returned from this trip it started out at about 2500 slowly crept up to about 2800 but wouldnt go any higher.
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Old 06-07-2010, 13:38   #6
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Check your exhaust elbow. Can't hurt.
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Old 06-07-2010, 13:51   #7
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did that pulled off the exhaust hose felt all up inside couldnt feel any coking up didnt really think that i would have any after only 3 yrs and 250 hours. i just felt from the outside up should i pull the whole elbow off and check it out
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Old 06-07-2010, 14:01   #8
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Maybe you could shine a light up there and do a visual check with a mirror.

Have you checked that all the linkages on your throttle cable are tight, that you can bottom out the throttle at the engine and that the cut off valve opens fully?

Does your engine have an air filter that may be causing an airflow restriction?

Does opening the engine room access make any difference?
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Old 06-07-2010, 14:03   #9
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thanks deepfrz i have checked the throttle the engine stops making any additional power at 3/4 throuttle and i still have more to go. have removed air filter to see if their was an air restriction but none and my engine room is huge so not that.
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Old 06-07-2010, 17:31   #10
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Well, if its not air (including exhaust) or fuel flow restriction then that pretty much leaves the prop.
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Old 06-07-2010, 18:59   #11
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What about injectors or a weak lift pump I've read somewhere that a weak lift pump will prevent the engine from hitting max revs
If it was prop related wouldn't it happen all the time
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Old 06-07-2010, 19:09   #12
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Yes, a faulty lift pump can cause a change in max power, in my experience.
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Old 06-07-2010, 19:12   #13
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Is there a way to test the lift pump or do I just replace it and hope for the best
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Old 06-07-2010, 19:32   #14
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To test? Turn it on, if it's electric, or pump the handle if it's mechanical. Open one of the bleed ports after and above the pump. Diesel should stream out.

I can hear the diesel dribbling into the tank from the return line when the pump runs.
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Old 06-07-2010, 19:39   #15
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Who specced the three blade prop for a one cylinder engine?
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