1997 Super Sport (GT-40) Cooling

[Gehenna]

Having a cooling problem on my 1997 SS. On our first trip out this year, I noticed that the temp would climb close to 200 while idling - once I was back up on plane, it immediately dropped back down to the 160 range. I figured this was an impeller issue so, I popped the RWP off and took a look. The impeller was definately in bad shape so I back-flushed all the lines and replaced it. This was my first time replacing the impeller and I assumed that the pump outlet was facing up and the inlet down and the pump should be mounted with the screw (that holds the inside plate in) should be facing away from the block. I should have taken a picture to make sure I re-mounted it correctly....

I took it back out to test things and within about a minute, I heard a weird rubber on metal noise and the temp started to climb again. I didn't even make it out of the marina. I pulled the RWP again and the new impeller was completely thrashed - all the way down to the hub. I figured I installed the new impeller wrong so I re-flushed all the lines and replaced the impeller again. This time making sure the fins were bent over against the housing in the direction of the pump's rotation. Just to be safe, I also replaced the thermostat in case it was stuck closed. I can't see that it was since on the first trip - after getting up to speed - the temp would drop back down. This wouldn't have happened if the thermostat was stuck closed...

At this point, as far as I can tell, it's just not pumping any water. The pump seems to be turning just fine, there doesn't appear to be any damage in the pump housing and the new thermostat seems to be opening but no water is making it to the block. After running at idle for 20-30 seconds, I pulled the inlet hose off the manifold and it appeared to be completely dry. I emptied the raw water filter canister and put it back on - not a drop of new water was pulled into it. I'm fairly certain that all of the debry from the last impeller was flushed out before installing the new(est) one.

I read in the service manual that the circulating pump failing usually wont cause the engine to overheat - especially at idle. Is there anything else i'm missing?

I'm completely lost here - any suggestions?

[pj]

RE: 1997 Super Sport (GT-40) Cooling

This just happened to me also. Make sure all of your hose clamps are nice and tight and the water strainer bowl is tight. My strainer was loose and the rwp would suck air at idle. Then once on plane, it would force enough water through to cool it back down.

[DanielC]

RE: 1997 Super Sport (GT-40) Cooling

I think your water pump is on backwards. I believe the screw should point to the block. Water travels the long way around the pump, the screw holds a cam that "Squishes" the water out the outlet of the pump.
Confirm the rotation direction of your engine, by cranking it. Rotate your water pump the same way, in a bucket of water to confirm that water comes out where you expect it to. Install your water pump, and feel the back of it to make sure it stays cool. STAY CLEAR OF ROTATING THINGS! If the pump gets hot, or you notice bubbles coming out from under the boat where the raw water pick up is, the pump is on backwards. Change it and try again. You might need a new impeller. V -drive boats take longer to draw water because of the length of the hose between the inlet and the pump.

[Gehenna]

Thanks for the advice. We've removed/tightened the bowl a couple of times during our troubleshooting. I'll give it a second look tonight.

I'll check the pump direction. We're such backwards mechanics it wouldn't suprise me if that were it.

[surroundsound64]

Even on my boat (direct drive) it can take up to a minute or longer before I actually get water out of the exhaust after the system has been completely drained. That is on a fake-a-lake too.

[jthooker]

Check your intake hose from the hull and see if it runs through the transmission intercooler before continuing on up to the raw water pump. If there was any water remaining in the intercooler over the winter it may have frozen and pushed one of the end caps loose. This will create an air leak that prevents the raw water pump from priming. Inspect both end caps very carefully. They are soldered on and could have been forced out just enough to crack the solder seal.

[DavidF]

Take a look at the engine ID tag on the intake manifold. If it starts with "PL" then the cam screw on the RWP should face toward the engine block. Opposite for "PR" engines. Your engine should be a "PL" engine.

[Gehenna]

OK, a partially collapsed hose and a loose hose clamp seems to have been [most of] the problem. We replaced the hose and tightened the clamp - temps are staying normal at idle and below 2000RPM. Anything above that and the temp slowly climbs to 180+ Not sure how much higher it will go - don't want to damage the motor. When I drop back down to idle, the temp imediately starts to drop down again.

All of the remaining RW hoses seem to be tight and in tact - same with the hoses from the manifold to the circulating pump. I've double checked the RW filter canister at speed and it doesn't seem to be pulling air. The thermostat is new but I boiled it anyway and it's opening up at 160, as it should. I pulled the top off the v-drive housing and made sure there were no obstructions in the waterflow there - anything else I can check?

jthooker, the shop we store the boat in during the winter is climate controlled - never gets below freezing. Thanks for the previous suggestions!