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Old 30 April 2019, 15:59   #1
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Question for the inboard engine crowd.

I had my engine removed last winter to replace the shaft on the water pump. On returning to service, I find that the plant is VERY reluctant to fill the raw water system after launching. I've had a couple of runs at it and worked around the issue by feverish water priming from buckets via the strainer basket and a rev in neutral. Once running, ops seem normal with visibly good circulation and normal temps under way and at idle.

Previously the system sucked in raw water without issue and filled the strainer basket in seconds. Other than the water pump replacement/engine out, I'm doing all the same stuff. The system is holding the water in place above sea level when the engine is off, so I'm not liking air leaks for the cause. I don't see any bubbles appearing in the strainer basket.

I don't like a mystery
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Old 30 April 2019, 23:43   #2
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Didn’t you antifoul recently? Did some get where it shouldn’t have?
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Old 01 May 2019, 01:36   #3
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Didn’t you antifoul recently? Did some get where it shouldn’t have?
I certainly did and I don't think so. I remove the intake covers as part of the prep, clean the first few inches of the intake passages and a/f the whole plant, using a sponge on a wire. No sponges were lost in this process. It's entirely possible there's a mussel up there somewhere but no sign of overheating per se. As the engine was out, one would hope that any wildlife got the shove, but it's on my List of Questions...
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Old 01 May 2019, 02:32   #4
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"Teaching granny how to suck eggs"

But you did get the impeller vanes pointing it the right direction as you fitted it?
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Old 01 May 2019, 04:08   #5
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Is the valve on the sea inlet fully open?
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Old 01 May 2019, 04:23   #6
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Is the valve on the sea inlet fully open?
No valve - direct feed from leg! Thanks though - keep the ideas coming lads
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Old 01 May 2019, 04:25   #7
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"Teaching granny how to suck eggs"

But you did get the impeller vanes pointing it the right direction as you fitted it?
New impeller fitted. Same mech as last few services. Possible but VERY unlikely.
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Old 01 May 2019, 05:26   #8
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Disconnect the raw water inlet, get a hose to it and back flush to check the flow back to the leg. If ok, connect the pump inlet to a bucket of water, start the engine and it should sook it up pronto. If both of those are good then swear a little and you'll need to check the outlet flow from the pump because if the water can't get out freely, it can't get in also. Report back.
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Old 01 May 2019, 06:42   #9
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Agree with JW - test the pump directly with a bucket if possible to rule out the rest of the inlet/strainer system, and check if the refurbished pump itself is good. I assume the impeller that was removed and replaced was whole, and no blades had been lost into the cooling system? Or potentially the new impeller has suffered infant mortality and popped a blade or two immediately?
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Old 02 May 2019, 00:36   #10
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I assume the zt370 only picks up via the leg and isnt tee'd to a through hull like the 6lp and bravo? Hopefully the inlet hose through the shield is larger on the zt as its woefuly inadequate to cool a large engine on the bravo. Could the problem be a displaced seal in the joint between the drive and shield? Or could there be a part corroded pencil anode dropped into the heat exchanger when being replaced?
I'm finding it hard to comprehend that the engine needed to come out to work on the rwp? Isn't it accessible in situ?
The impeller vanes backwards is a red herring they flip the correct way as soon as it starts to turn
If it was an older engine I'd be suspecting a possible worn pump/end plate but on something as new maybe not and presumably the engineer had a good look at the pump while it was off.
Bit of an odd one & be interested to hear the solution
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