Join Date: Dec 2012
Location: Vancouver BC
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Re: yanmar vibration at low rpm
In considering your dilemma, some things to note. The relationship between fuel delivery and load in forward and reverse are different and therefore the conditions are not matched at the same rpm, so the question is, what occurrences are there which could cause your problem which also correct themselves? Considering that the VE pump is the one component which is constantly transitioning itself between springs, hydraulic pressures and centrifugal forces, all of which are much more likely to show their flaw at lower rpms, my money is on your fuel pump. Pump characteristics change as they warm up and sometimes they change for the better, and sometimes not. My advice would be to have the pump removed and tested/reclalibrated specifying that you have this problem. Any fuel tech worth his 10 coffees will be able to sort this out for you.