I have a Yanmar 30QM freshwater cooled. It runs close to the alarm. Thermostat and impller looks good. Does any one have any suggestions on what to check. Also thinking about cleaning seawater side of Engine and would like suggestions on how to do.
Yanmar engine runs hot
- Thread starter chap769
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First, check the volumetric water flow......
At 1400 rpm the 3QM30 should be putting 13.3 liters per minute / 3.5 gallons per minute of cooling water out the exhaust. Just use a bucket of known volume and a stop watch. If the flow is much less than this specified volume, then check for pieces of broken impeller vanes, etc. blocking the system downstream of the pump, worn out impeller vanes or a worn out pump cam, etc. A defective exhaust manifold thats falling apart internally (slab rust) or a fouled inlet strainer can also cause this. If the volume flow is close to specified, then consider to 'pickle' the engine with a commercial boiler descaling compound such as Marsolve or Rydlyme to dissolve the fouling carbonates in the heat exchanger and exhaust manifold. You can pickle with muriatic/hydrochloric acid but inorganic acids will also dissolve engine metal. The boiler descalers wont dissolve metal. www.marsolve.com.
At 1400 rpm the 3QM30 should be putting 13.3 liters per minute / 3.5 gallons per minute of cooling water out the exhaust. Just use a bucket of known volume and a stop watch. If the flow is much less than this specified volume, then check for pieces of broken impeller vanes, etc. blocking the system downstream of the pump, worn out impeller vanes or a worn out pump cam, etc. A defective exhaust manifold thats falling apart internally (slab rust) or a fouled inlet strainer can also cause this. If the volume flow is close to specified, then consider to 'pickle' the engine with a commercial boiler descaling compound such as Marsolve or Rydlyme to dissolve the fouling carbonates in the heat exchanger and exhaust manifold. You can pickle with muriatic/hydrochloric acid but inorganic acids will also dissolve engine metal. The boiler descalers wont dissolve metal. www.marsolve.com.
Hot Yanmar with good impeller
I had the same problem with my Yanmar. I replaced what appeared to be a good impeller but the idiot thing continued to run hot and sort of degraded from there. I finally gave up and had someone else look at it. What he found was a clogged pipe from the water pump to the block. He pulled out about a 50-cent ball of impeller parts from a previously replaced impeller. Not that this is what is causing your over heating problems but it sure fixed mine.
I had the same problem with my Yanmar. I replaced what appeared to be a good impeller but the idiot thing continued to run hot and sort of degraded from there. I finally gave up and had someone else look at it. What he found was a clogged pipe from the water pump to the block. He pulled out about a 50-cent ball of impeller parts from a previously replaced impeller. Not that this is what is causing your over heating problems but it sure fixed mine.
Had same problem w/my 3 cylinder Yanmar. Was running without raw water strainer, sucked up grass & debris was restricting water flow. Solution was to clean raw water heat exchanger. Have since added raw water strainer. No more problems.
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