4.3 GXI SXA no water coming from seawater pump

[_sadpanda]

The following are all new

• long block
• circulation pump
• thermostat
• seawater impeller, housing, o-ring, backplate
• outdrive gaskets (upper to lower, upper to gimbal)
• transom to outdrive water tube
• transom water neck
• heat exchanger and hose to transom
• bellows, bearing

Stage one was long block and all of the engine side bits (cracked cylinder head due to freezing) After install it held temp when attached to hose via flush port and while idling in the lake. However, pop up on plane and it would quickly over heat and not recover back at idle. It was also destroying the sea water impeller.

At that point I replaced the housing, mounting plate and yet another impeller, same issue.

Boat was run in salt water for 8 years and the outdrive has the corrosion to prove it so I figured outdrive seals. Replaced all of the listed outdrive bits and it good on flush port but overheats idling in the lake. Interestingly it did not destroy the impeller, still looks new.

So I ran a compression test, all cylinders pump up the same and reach the same pressure after 4 strokes (170psi)

I removed the thermostat, verified steam hole was clear and tested it in a sauce pan on the stove (opened at 160ish, did achieve full travel)

I rigged up a way to pressure test the entire cooling system - blocked off the outdrive inlet, removed the exhaust elbows and sealed the riser water outlet, removed the impeller, put an air line on the flush port via a garden hose to 1/4 compression adapter. My exhaust blockoff wasnt perfect but I was able to maintain the 10psi I set the regulator to and soap all connections. No leaks.

I finally put a rubber water trough under the outdrive, filled it with water, disconnected the seawater hose from the thermostat and fired it up... No water.

How does a new impeller and housing not draw water?

Any ideas?

 

[Scott Danforth]

You should be able to pressurize to 15psi, shut off air and it should hold that 15psi forever

Attempting to suck up from the trough just toasted your impeller. Always use muffs

 

[alldodge]

Check the connection where the outdrive connects to the hose leading to the raw water pump. They get clogged up

 

[_sadpanda]

Correction, I do have water... I just had to give it a little more time to prime.

Not exactly a gusher but it is moving water (pic)

So I reconnected it and idled. Held temp no issue. Then I blocked the exhaust a bit to give it some more realistic back pressure. Temp started to climb and would not recover. I disconnected the sea water hose from the t-stat housing and sure enough, no water. After shut down for a bit I unplugged the exhaust, re-fired with hose disconnected and once water was flowing I reconnected... Temp held at target.

I'm thinking drive was sucking air, toasted a head gasket and now its pressurizing the waterjacket.

I never run on muffs out of water, only flush port. Is there a kit or better way to seal the exhaust for pressure testing? I could cap the line from the tstat to the exhaust risers but that takes takes them out of the equation.

I will check impeller.

 

[_sadpanda]

Check the connection where the outdrive connects to the hose leading to the raw water pump. They get clogged up

see list of new parts... Old hose was not clogged. New hose is, well, new. The idling issue was the first test outing. Didn't even make it off dock, so not likely to be clogged.

 

[Scott Danforth]

You have to get water up over the drive to prime the pump.

Raw water pumps don't draw water, they only push water

You toasted the impeller.

 

[_sadpanda]

You have to get water up over the drive to prime the pump.

Raw water pumps don't draw water, they only push water

You toasted the impeller.

That may be correct now that I have run it in a tub.

That does NOT explain the overheating at idle in a lake that happened yesterday.

 

[Scott Danforth]

Replace the raw water impeller, check the raw water casting at the drive

 

[_sadpanda]

You have to get water up over the drive to prime the pump.

Raw water pumps don't draw water, they only push water

You toasted the impeller.

Thanks for the replies but this is not the case.

These impeller style pumps are used everywhere, self priming and can do so with several feet of lift. No published specs for the Volvo unit but here is a manufacturer's site for stand alone units.

Could someone potentially damage an impeller in this manner? Sure, especially if there are other issues, however, testing in this manner is not automatic death for the impeller. See photos below. Foreground is the impeller in question, background is the backup/spare it replaced a number of seasons ago.

When I separated the housing to replace the toasted impeller I found some of the blades were angled back the wrong direction. I simply flipped the impeller over and re-installed... Problem fixed. I've got nearly 3 hours on it and zero issues.

 

[_sadpanda]

Really, you guys shoulda hit me with 'check the stickies' as the Volvo gas engine overheating diagnostics manual is THE place to start if the impeller is good.

Posting my implementation here, hope it helps someone in the future

 

[Scott06]

Really, you guys shoulda hit me with 'check the stickies' as the Volvo gas engine overheating diagnostics manual is THE place to start if the impeller is good.

Posting my implementation here, hope it helps someone in the future

so if you have zero issues in three hours why did you insert clear hoses ?

 

[_sadpanda]

so if you have zero issues in three hours why did you insert clear hoses ?

Had issues after re-sealing the outdrive. Brought it in, installed clear hoses and inspected impeller, took it out for testing issues resolved. The only thing I changed was when I re-installed the impeller, I flipped it.

Lesson here is the impellers end up with a 'memory' and if you do a remove/inspect/reinstall, be sure to orient it the same way it came out otherwise you may end up with cooling issues

 

[flashback]

Your diagnosis is true but because you reversed it the life of the impeller will be shorter..