Impeller Not Priming

h2ohangtime · May 31, 2022

Is it possible/common for a grenaded impeller to warp the housing? Boat is a 2007 Typhoon with the 5.7 Black Scorpion. Impeller shredded on the trailer during spring cleaning and setup—no problem, I thought. Cleaned out the housing (have all 8 splines) and found no debris in the transmission cooler or anywhere else downstream. Backflushed everything I could. Installed new impeller and upgraded plastic pump housing cover with the wear plate. Also R&R’d the thermostat while I was at it.

The issue is that the impeller is not priming/pumping water. With the engine running and water flowing into the pump (installed T and hose fitting in the output of the V-drive), there’s no water reaching the transmission cooler. This tells me it’s one of two things:

an ill-fitting impeller
the pump housing was warped when the original impeller shredded

Is there anything else I should be checking? I DO get a lot of water flowing out the thru-hull intake as it goes backwards through the v-drive, but the pump still wasn’t drawing water when in the lake, either. I have NOT tried to rev the engine to get the pump to prime, but maybe that’s the next test? I certainly don’t want to overheat again.

I’m at my wits' end trying to figure this out and get us on the water. Appreciate any other ideas you have.

*** Cross-posted @ Wakeworld ***

jtryon · June 2, 2022

the priming thing happened with mine when i was doing my first impeller change after buying the boat. the PO didn't use it much in the 5 years he owned it so must have never changed it, and the old one wore a ring where it rides against the pump housing. i see you already installed the plate that goes between the two halves of the housing to fix the issue when you install a new impeller.

call Steve Buttrick at C&S Marine Pumps. i got my impeller from him, and when i went to install it he had included a note in the box that stated this exact issue being common for the Merc motors. super good guy to work with a he was a fraction of the cost of others that i was shopping around. i bet he can talk through what it would take to get yours fixed.

C & S Marine Pumps Inc

149 s Highway 97

Cantonment , Florida 32533

Cell (850) 380-1731

Edited June 2, 2022 by jtryon