Cooling system, Model: 5.7L EFI GM 350 V-8 1998

[John Evans]

I have a sea water cooling system. Testing the fuel pump replacement running on muffs i began to over heat. I shut the engine down, I checked and saw that no water had been expelled with the exhaust, the out put side of the water pump had water in the hose, I tapped the thermostat housing with a wrench and started it again. It ran good cooled down and was spitting out water. I let it cool down and ran it a few times with the same result running hot no or very little water expelled, I stopped it each time before I got too hot.

So what's your best guess, Thermostat or water pump impeller?

 

[dubs283]

Re: Cooling system, Model: 5.7L EFI GM 350 V-8 1998

a water pump impeller has a higher rate of failure than a thermostat, im gonna go with water pump impeller

 

[jopes]

Re: Cooling system, Model: 5.7L EFI GM 350 V-8 1998

impeller, you should have water coming out even if the Tstat is closed.

 

[John Evans]

Re: Cooling system, Model: 5.7L EFI GM 350 V-8 1998

Replacing the impeller notices that the body seemed galled needs to be replaced anyway but I also cracked the inlet fitting for the hose.

Are all of the replacement body kits plastic? If you get the oem pump kit for around $350 is that metal or plastic also? Should I splurge and get one of the brass pumps out there for around $450? Are there benefits to buying the more expensive pumps other than it may be harder to break the inlet or outlets?

 

[Don S]

Re: Cooling system, Model: 5.7L EFI GM 350 V-8 1998

I guess that means you have a Bravo outdrive, correct? With the belt driven raw water pump.
Yes, they are all plastic. What causes the pump housings to become galled up is running dry. They just do not like being run dry.
The kit number (plastic housing) 46-807151A14 lists for $110, not 300.

they are also aftemarket http://www.iboats.com/Water-Pump-Ki...5665735--**********.409437630--view_id.172770

Personally, I would get the OEM part. Even though it's a bit more expensive. I have used both, that's why I would stick with OEM.

 

[John Evans]

Re: Cooling system, Model: 5.7L EFI GM 350 V-8 1998

I did as you suggested with success. 15min on the muffs, steady at 175deg putting out a ton of hot water. So there it is, fuel pressure problem solved, Water pump fixed, all I have to do now is re-install the seats and deck plate and we're on the water.

Thanks to all that have been great help.

JCE

 

[Jimbob Austin Tx]

Re: Cooling system, Model: 5.7L EFI GM 350 V-8 1998

I belive it is your water pump impeller.
I have same engine and last month replaced engine water pump assy and thermostat.
Same problem- temp runs about 185F and rises to 200F over time (should be ~165F).
When I took off the thermostat and water pump, I found rubber parts lodged in thermostat and water pump housing that looked like rubber impeller fins. After looking at Sea Water Pump assy, these rubber parts looked just like the fins on the impeller.