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Discussion Starter #1
I noticed recently that the engine temp creeps up toward the "red" zone when I motor at high (cruising) rpms. If I back the throttle down the temp dial goes down as well.

If this is accurate the coolant temp is heating up at high revs. There is normal water being expelled.

Is there SOME blockage in the system which "starves" is of water flow flow needed at higher revs?

Would it help to run barnacle buster or similar through the raw water circuit of the engine? If so for how long?
 

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bell ringer
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Just a little scale in the hx tubes is a LOT of lost heat transfer.
Also since water flow and rpm go together it would be hard to tell difference of 80% and 100% flow due to a clogged elbow.

You have of course checked the strainer and that the inlet isn't blocked ? And that the pump impeller is good?
 

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Discussion Starter #3
Just a little scale in the hx tubes is a LOT of lost heat transfer.
Also since water flow and rpm go together it would be hard to tell difference of 80% and 100% flow due to a clogged elbow.

You have of course checked the strainer and that the inlet isn't blocked ? And that the pump impeller is good?
Hasn't been out of the water.... inlet strainer could be fouled... a diver could clear that.
 

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bell ringer
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Hasn't been out of the water.... inlet strainer could be fouled... a diver could clear that.
what difference does not being out of the water make?

People find all kinds of things in their seawater inlets, fish, weeds, rags, jelly fish. I would take off the hose and check before chasing down something harder to do.

If the sw line is all clear I would next be checking the pump.
 

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Engines do run hotter at higher rpms, but something is failing to cool yours back down. All ideas above are what I’d check. Assume you changed your impeller during spring commissioning. When is the last time you descaled the Hx?
 

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Discussion Starter #6
what difference does not being out of the water make?

People find all kinds of things in their seawater inlets, fish, weeds, rags, jelly fish. I would take off the hose and check before chasing down something harder to do.

If the sw line is all clear I would next be checking the pump.
Thanks Don. exterior strainer is a grooved tear drop shape with slots... easy to foul. I of course clean it when the boat is hauled... and diver does lot in season. Too cold upo here for divers.

Pump is not even one season of light use... not the pump.
 

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You replaced your pump last season, or just the impeller?

Impellers, sitting in one place all winter can deform.
 
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