Thread: FWC Ranger 33
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  #2   IP: 12.172.250.194
Old 08-03-2017, 06:42 PM
tenders tenders is offline
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There probably isn't supposed to be any restrictive valve at all in the raw water system, except for the seacock just inside the hull.

Seems like you need to validate whether the pump is pumping properly, or whether something inside the cooling system is restricting flow. Disconnect the pump at the outlet, direct the outlet overboard or somewhere manageable, run the engine, and see what happens. You should be deluged with water. If you aren't, and you've done all this to the pump, I can only think of a few problems: the intake may be plugged, the impeller might be the wrong size for the pump and leaking water within the chamber, or the "shoe" in the body of the pump that compresses the vanes of the impeller as it spins is worn and isn't providing compression.

If the pump is working then you probably have a restriction inside the cooling system. Usual Suspect #1 is a piece of an old impeller that broke off and was pushed in somewhere inconvenient. Usual Suspect #2 is rust chunks or flakes that broke off and lodged in a totally different set of inconvenient places. Sometimes backflushing the engine can send them out from whence they came, but don't do that with a lot of pressure (ie, don't use city water pressure) - that's too much of a good thing.
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