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Vessel Name: marian J
Engines: Cummins 6BTA5.9M 1989 CPL 953
Location: long island new york
Country: usa
twin 1989 6BTA5.9 250 HP CPL 953, 1760 hours
Having a temp problem on port engine. Coolant temp creeps up as I run, If I run about 2200, the port engine temp will gradually increase to 175. At 2250 it will creep to about 180 and at 2350 it creeps up to 185 or so and then I’ll pull throttles back and it cools off. Very repeatable so I don’t think this is a gauge/sendor issue. Stbd. engine runs about 165 and will stay there all day long no matter what RPM I run.
I have Tony’s 160 deg thermostats. No other coolant upgrades. corner expansion tanks, do not have TA recommended 1 inch banjo and hoses etc. I can see TA shaking his head already. Both engines always ran the same temp. I put new SW impellers in this season. Heat exchangers were changed several years ago and I descaled both engines a couple years ago.
The port side overflow tank ended up about 1 inch higher even after the engine cooled down and the expansion tank was low on coolant. the stbd engine overflow tank went right back to normal level after the engine cooled down.
I pressure checked the coolant system cold with a STANT pressure tester and it holds pressure. The rad cap is fairly new as well. I’m not sure if the 2 issues are related….
thoughts?
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Vessel Name: overslept
Engines: Twin 4BT CPL741
Location: Massapequa Park, New York Long Island
Country: USA
As these engines age some of the fittings will also start to scale up. You stated you changed the heat exchangers and descaled the blocks too.
You should inspect the small fittings (that Tony says to change) to see if they are scaled up and not allowing the proper flow.
You could also change the water pump (not the raw water pump, the water pump for the fresh water side). Possibly this is not flowing as well as the starboard engine.
If you believe this is not a gauge issue then I would check these two things. Water pump is a simple job as well and not to bad on the wallet. I am not saying to just throw parts at it, but if the water pump is 30 yrs old you cant go wrong replacing it.
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