Hi all,
Recently bought a 1989 Hunter 33.5. For some reason the installed engine is a Yanmar 2GM (raw-water cooled), as opposed to a 2GM20F which I believe came OEM. Anyway I am planning to do all the minor maintenance on it (oil filter, air filter, fuel filter, water impeller, and thermostat replacement) to freshen it up, and I'd also like to do a flush just for good measure. The engine doesn't seem to be spitting out as much water out of the exhaust as I have seen on some videos so I am hoping that is caused by an old impeller, but it also might be caused by scaling. I did some research and saw that Yanmar recommends doing the flush with Rydlyme descaler, so I ordered some. But, from reading the posts from people who have done the flushes, the approach seems to vary:
1) Remove the seawater suction and, while running the engine, have it suck from the descaler bucket (emptying back into the bucket).
2) Similar, but instead of running the engine, just use a separate 12V pump like a bilge pump to circulate the fluid.
3) Backflush the system with the fluid and a separate pump, so the flow goes opposite the normal flow path.
I am inclined to try the backflush route because that would seem to have the best chance of dislodging any solids or material which may have gotten sucked into the engine and might be clogging a passage, such as bits of old impeller. But not sure if that theory works better in my head than it would in reality. So would appreciate any insight you all have about the various different potential approaches that seem to be in use.
Thanks much
'Dubs
EDIT: Prior to me owning it, the boat was in saltwater, but now it is in a freshwater lake, if that makes a difference.
Recently bought a 1989 Hunter 33.5. For some reason the installed engine is a Yanmar 2GM (raw-water cooled), as opposed to a 2GM20F which I believe came OEM. Anyway I am planning to do all the minor maintenance on it (oil filter, air filter, fuel filter, water impeller, and thermostat replacement) to freshen it up, and I'd also like to do a flush just for good measure. The engine doesn't seem to be spitting out as much water out of the exhaust as I have seen on some videos so I am hoping that is caused by an old impeller, but it also might be caused by scaling. I did some research and saw that Yanmar recommends doing the flush with Rydlyme descaler, so I ordered some. But, from reading the posts from people who have done the flushes, the approach seems to vary:
1) Remove the seawater suction and, while running the engine, have it suck from the descaler bucket (emptying back into the bucket).
2) Similar, but instead of running the engine, just use a separate 12V pump like a bilge pump to circulate the fluid.
3) Backflush the system with the fluid and a separate pump, so the flow goes opposite the normal flow path.
I am inclined to try the backflush route because that would seem to have the best chance of dislodging any solids or material which may have gotten sucked into the engine and might be clogging a passage, such as bits of old impeller. But not sure if that theory works better in my head than it would in reality. So would appreciate any insight you all have about the various different potential approaches that seem to be in use.
Thanks much
'Dubs
EDIT: Prior to me owning it, the boat was in saltwater, but now it is in a freshwater lake, if that makes a difference.
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