Under power, about 2200 rpm, from Block Island to Duck Island Roads,CT (45 mi.+/-), our 3 yr.old 50 hp Yanmar Diesel began to lose power (about 700 rpm) for no apparent reason and then regained. This happened several times. We were operating on approx. 1/3 tank fuel (forward tank). Weather calm, light winds. The engine never stopped but faded like it was going to die. Next day cruised to Port Jefferson (35 mi.+/-)under power and had no problem. Next day moving boat from anchor to mooring, similar event occurred once. Planning to bring the boat south at the end of September and would certainly like to find out what causes this before we get underway.
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Jeff
Fuel Filter
Had a similar problem on a boat last spring between Florida and the Bahamas. If you haven't changed the primary fuel filter in a while it may be clogging up. A fuel tank that is not full may have some algae growth in it. We changed out the primary filter and that solved the problem...
Had a similar problem on a boat last spring between Florida and the Bahamas. If you haven't changed the primary fuel filter in a while it may be clogging up. A fuel tank that is not full may have some algae growth in it. We changed out the primary filter and that solved the problem...
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Dave
Yep - fuel filter
I concur - likely the fuel filter. Cheap to replace and, if in an accessible location (a big if), relatively easy to change.
I concur - likely the fuel filter. Cheap to replace and, if in an accessible location (a big if), relatively easy to change.
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Paul
Check the prop, too.
I had similar symptoms caused by a piece of rope wrapped around the prop shaft. We picked up said rope on the same stretch of water, almost certainly from a lobster trap. It probably is the fuel filter, but you should put on your mask and check the prop shaft, too. Paul sv Escape Artist h336
I had similar symptoms caused by a piece of rope wrapped around the prop shaft. We picked up said rope on the same stretch of water, almost certainly from a lobster trap. It probably is the fuel filter, but you should put on your mask and check the prop shaft, too. Paul sv Escape Artist h336
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ken
air
Had the same problem with my Yanmar. It turned out to be air getting into the system through a loose support holding the raycor filter. Once the air leak was corrected, the engine ran fine
Had the same problem with my Yanmar. It turned out to be air getting into the system through a loose support holding the raycor filter. Once the air leak was corrected, the engine ran fine
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Debra B
dirty fuel
Desiel will grow the most annoying stuff in the bottom of the tank. Check the filters, and if they are really bad, you may need to get the tank and fuel cleanned.
Desiel will grow the most annoying stuff in the bottom of the tank. Check the filters, and if they are really bad, you may need to get the tank and fuel cleanned.
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Derek Rowell
Fuel pick-up tube filter clogged?
Had the same problem with my 3 cylinder Yanmar on my Hunter 34. Turned out that the fuel line pick-up tube had a gauze filter in the end that was completely clogged with black goo. Took the gauze out and installed a Racor primary filter. That was the end of the problem.
Had the same problem with my 3 cylinder Yanmar on my Hunter 34. Turned out that the fuel line pick-up tube had a gauze filter in the end that was completely clogged with black goo. Took the gauze out and installed a Racor primary filter. That was the end of the problem.
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Allen
I also had the same problem....
I had the same problem with my 3 cyl. 27 hp Yanmar. I changed the Racor filter and then pumped and filtered the fuel tank. It was filthy. So then I set out for a weekend of cruising.....and 5 miles from port it happened again. This time, I got a mechanic involved and we (he) decided that I had a pin-hole air leak in the fuel line. We replaced it and it runs great at the pier...I guess I'll find out this weekend whether or not that was the problem.
I had the same problem with my 3 cyl. 27 hp Yanmar. I changed the Racor filter and then pumped and filtered the fuel tank. It was filthy. So then I set out for a weekend of cruising.....and 5 miles from port it happened again. This time, I got a mechanic involved and we (he) decided that I had a pin-hole air leak in the fuel line. We replaced it and it runs great at the pier...I guess I'll find out this weekend whether or not that was the problem.
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MaySail
Thanks for good information
This past winter we had the boat hauled, fuel tanks emptied, new fuel, biocide, fuel filters - the whole bit. We will check on the tightness of the filters for air leaks, and take a look at the prop. Big thanks again!
This past winter we had the boat hauled, fuel tanks emptied, new fuel, biocide, fuel filters - the whole bit. We will check on the tightness of the filters for air leaks, and take a look at the prop. Big thanks again!
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Dave
It only takes one tank
Don't discount the dirty fuel, thus dirty fuel filter. Even with all the work you did last winter, it only takes one bad tank of fuel to create the problems you described.
Don't discount the dirty fuel, thus dirty fuel filter. Even with all the work you did last winter, it only takes one bad tank of fuel to create the problems you described.
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Pete Peterson
Vote for filter
Now that you described what you did last winter, I vote for the fuel filter too. If all you did was empty the tanks (and not have them cleaned), you may have stirred up debris from the bottom, which then clogged up your brand new filter. I've heard recommendations that you should change fuel filters twice a year - once at the end of the season, and then again after a few hours of motoring at the beginning of the next season.
Now that you described what you did last winter, I vote for the fuel filter too. If all you did was empty the tanks (and not have them cleaned), you may have stirred up debris from the bottom, which then clogged up your brand new filter. I've heard recommendations that you should change fuel filters twice a year - once at the end of the season, and then again after a few hours of motoring at the beginning of the next season.
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