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Old 01-31-2015, 12:19 PM   #11
Ski in NC
Technical Guru
 
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City: Wilmington, NC
Vessel Name: Louisa
Vessel Model: Custom Built 38
Join Date: Jan 2014
Posts: 6,194
I've been in the marine engine business for almost 20yrs. I understand just about everything about these beasts- except trying to understand impeller life. I have seen impellers at least 10yrs old with lots of sitting time- look perfect. I have seen others coming apart after 100hrs with very little sitting time.

A few patterns are noted: The Jabsco's on Detroits seem to last forever. Sherwood impellers on Cummins don't. Mine included. Not only is the pump arguably a POS, but the impeller on mine likes to load the aftercooler with vanes even with little sitting time.

Mine can go 200hrs, I change the AC zinc and there are vanes. Hmm, where did they come from??!! Change impeller, yep in rough shape. Go another 200hrs, no vanes in AC. Go another 200, no vanes, ok. Get ready for long trip, put new impeller in just to be sure. Old one has 400hrs, looks great. Go on trip, put about 200hrs on new imp, change zinc on AC. Vanes in there. Great. 200hr imp coming apart!! Get p'd, put the 400hr imp back in. I think I have put another 400 on it, so now about 800 total. Checked aftercooler, no vanes.

Getting ready for another trip. So roll the dice and run on the 800hr one, or roll the dice and put a new but iffy one in???

These are all new impellers in factory Sherwood packing, bought from same vendor.

Go figure.

They last forever until they don't.
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