seawater pump

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George DuBose

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Jul 30, 2024, 8:16:33 AM7/30/24
to 'Peter Ogilvie' via pearson-boats
The Yanmar 3GM30F stopped mixing water with the exhaust causing the
engine to overheat. I checked the seawater filter, checked the seawater
pump, opened up the heat exchanger and all the tubes were open, pulled
off the exhaust manifold and elbow, neither were incredibly dirty.

I was thinking I might have to clean the waterlift muffler, but after
installing a new seawater pump, all was fixed and back to normal.

The Johnson raw water pump was 19 years old and ran for over 3000 hours,
I change impellers regularly, but apparently the cam inside the pump was
worn enough to stop pumping.

Besides buying a new Chinese copy of the raw water pump (which actually
looks quite good and even with some minor improvements over the
Johnson), I bought a rebuild kit and hope to repair the original pump to
be a backup.

Anyone else had a seawater pump give up the ghost due to old age?

George/Skylark

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Stephen Craft

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Jul 31, 2024, 10:23:14 AM7/31/24
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Hi George,
I have found the last two years that the raw pump will not pull from a 5 gallon bucket at the beginning of the season.
If I prime it with a pump, everything is ok from then on. I have not replaced the impeller, but it is easy to identify cracks in the rubber tangs, suggesting replacement.
Stephen

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Dave Cole

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Jul 31, 2024, 10:31:51 AM7/31/24
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George,

When you say "cam inside" do you mean the interior shape of the pump where the rubber impeller ride against?

3000 hours is a lot of time.

Is your engine ok.  It survived the overheat ok?
Do you have an overheat alarm on your engine?

Dave
10M #26


George DuBose

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Jul 31, 2024, 10:43:32 AM7/31/24
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RESPONSES IN CAPITAL LETTERS FOR CLARITY


George,


When you say "cam inside" do you mean the interior shape of the pump
where the rubber impeller ride against?
YES AND IN MY REBUILD KIT FOR THE OLD PUMP THERE IS A REPLACEMENT CAM.

3000 hours is a lot of time.
I BABY THE YANMAR. CHANGE THE OIL AFTER EVERY LONG TRIP AND EVERY WINTER.

Is your engine ok.  It survived the overheat ok?
Do you have an overheat alarm on your engine?
YES, THANKS TO THE OVERHEAT ALARM, I TURN THE ENGINE OFF RIGHT AWAY. I
HAVE TO RUN THE ENGINE AGAIN TO GET INTO MY SLIP.

ALL IS GOOD NOW. THANKS GUYS

Dave
10M #26

George DuBose

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Jul 31, 2024, 10:44:32 AM7/31/24
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I probably change my impeller every year or two at the latest.

George
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