Excalibur 330 Impeller not drawing water

[JayG80]

My 2007 Ski Nautique isn't drawing in cooling water.

I winterized the boat and when returned to operation, noticed the analog temperature gauge wasn't functioning. Based on advice in another thread, I replaced the thermostat.

Can replacing the thermostat & gasket cause an air leak that is creating my issue? T-stat is downstream of the impeller. I did re-snug thermostat bolts, the was gasket installed dry. Should I apply gasket sealer?

History:

Removed strainer bowl and put new teflon tape on the plastic fittings then reinstalled. No help.

Primed the strainer bowl with water and boat ran fine. Able to ski 1 set. Temp gauge worked properly.

Next time out, it will not draw water into strainer. Tried revving engine, no luck. Have tightened all hose clamps with nut driver.

Replaced impeller twice due to running while dry. They both had a minor rash but not missing chunks.

Eliminated strainer by running an intake hose from a bucket feeding hose into the trans cooler. https://youtu.be/AE37Gt70DF8?si=qvGIQp6tZWcYalQg

Engine drew water down about an inch and quit pulling water.

That's where I am, what next?

[teamseal]

check the on hub on the impeller and see if it is spinning in the rubber.
where did you get your impeller?

[JayG80]

Thanks Jody, the impeller isn't spinning on its hub. I'm on the 2nd impeller in a week and it is a PCM RP061022 from nautiqueparts.com. Changed o-ring each time.

Can thermostat gasket without sealer cause an air leak?

[SilentSeven]

I see you said you checked the hose clamps but this really sounds like a classic air leak on the water draw side of raw water pump.

I'd recheck all the hose clamps for tightness at each water feed line. Inspect each line from the through hull pickup to the raw water pump. If one is loose (or there is a hole in the water line), the pump will not lift water.

Other items to look at:
- Your thru-hull shut off valve is fully open right?
- Have all the winterization plugs been re-installed and are snug? Specifically check with transcooler drain plug.
- Does the water feed line have any tee's for things like showers or water temp gauges. Look at them closely for leaks.
- I'd also make sure there's a good o-ring in the water filter. I've never had to use teflon tape.


Let us know what you find out!

[core-rider]

Anytime I remove the raw water pump/impeller I refill the entering hose (to the raw water pump) with water before starting. Those raw water pumps don't like pulling water dry and require priming. I also use some Dawn dishwashing soap to help lube the impeller on first start.

Make sure you have the thru-hull open, strainer is full of water, hose from strainer to raw water pump is full of water and try again. If you see air bubbles in the strainer while running, then you have an air leak there likely at the O-ring gasket. The thermostat housing will show a leak if you're moving water by leaking out of the housing. Effectively that's the pressurized side of the system after the raw water pump and won't affect its operation.

[JayG80]

Thanks Guys, Update - problem eliminated. Tranny plug was not tight enough and created air leak.

I knew it was probably an air leak and had installed a new strainer and barb fittings because I suspected a bad bowl gasket or what might be a hairline bowl crack. That wasn't it.

I filled the engine side hose from the strainer full with water until it backed up and also filled the strainer bowl. Ran the engine, only to empty the bowl but not refill it.

Previously tightened clamps and plugs but decided to add new Teflon tape to the transmission cooler drain plug. That plug's brass threads show wear. I added new tape and threaded the plug in about 3/4 of the way. It was previously only threaded in about 1/2 way. Fired the engine and it is drawing water into the strainer and temp gauge ran up to normal.

Will order a new brass plug soon. I am always cautious of over-tightening the brass plugs after I nearly stripped out the exhaust risers in my '99 Moomba.

My 2007 Ski Nautique EX 330 came with a water strainer feeding 1.25" hoses into 1" strainer fittings. I replaced it with the same 1" strainer threads. Just had someone tell me it should be a 1.25" strainer threads for the 250 to 450 hp engines.