Join Date: Sep 2010
Location: Boston area
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Rep Power: 6
Re: Yanmar 3GMD sudden increase invibration
Thanks for the ideas. The motor is 1985, but only 500 or so hours. I have had it for past three years, and prior owner had it for around 8. Professionaly maintained by him, partly DIY by me. Interestingly, the prior owner was aboard with me when the vibration started - the first time he had been back aboard. I keep it in the Piscataqua River just up from Portsmouth Harbor, and run it for a least a half hour each way in and out of harbor. River is a very fast current, one of top three tidal estuaries in the US I am told, so the little Yanmar is worked pretty well - never just loafing and not well warmed up. I have put around 100 hours on it to date, with pretty flawless performance. It is very up to date for maintenance. All new wiring harnesses, impeller, hoses, all filters, shaft/cutlas/motor mounts, belts, mixing elbow removed and cleaned last season (didn't need it), etc. Racor replaced in spring, looked clear through the glass, but I didn't open it yet. Fuel is of mixed age - did my first 2012 fill a couple of weeks back, for 8 gallons used so far this season. Tank holds around 14 gal. so rest of it is still from last year. Always keep additives for biocides as well as water, etc. and bottom of tank (seen through the fill pipe) is mostly shiny, with a few visible black bits on bottom. No smell of any fuel leakage, no smoke of any kind, no odd noises, etc.
I will get into it tomorrow, and at lesat eliminate several possible sources. Good to know that I can open the decompression levers at any time, not just when starting (never have needed to do this with any diesel so far).
1985 Marshall 22 catboat