Wizard Of Eyez
Recruit
- Joined
- Jul 13, 2011
- Messages
- 4
First a little history... I have a 1994 23 ft Sportcraft with a Volvo 5.7 GL. Normal operating temp has been 150. Earlier in the year on the maiden voyage it heated to 225. I took her home and replaced the impeller and thermostat. While waiting for parts I discovered the real problem. The in take hose between the outdrive and the impeller was clogged solid with stinkbugs. I could barely blow air through it. After clearing that and replacing the parts she still heated up.... but then the temp ropped like a rock after a bit back to 150. Made me think that, due to a higher water volume to the pump, I blew more bugs out from the system beyond the impeller and pump. Then for a month and alot of use everything was perfect until yesterday. I had 4 big guys out Friday with no problem. Yesterday was another story.
Right from the dock she went to 225. I removed the thermostat and she ran cold as expected. 110 on plane and 125 to 150 while trolling depending on my rpms. OK... thermostat right? Not so fast.... after about 2 hours of slow trolling around 800 rpms I notice shes up just a little to 160. Odd since nothing changed (speed/rpms). While staring at the temp guage she goes to 200. So I bump the rpms a little to 1000 (5 mph) and apparenty due to a higher water volume she cools right down. Only now If I go back to 800 rpms the temp will come right back up to 200.
My only 2 guesses are either 1) water pump or 2) more bugs causing a clog beyond the impeller and pump.
Under these circumstances it appears the sea water pump is working properly. Otherwise I'd overheat regardless of rpms correct? If I take the plug off of the top of the water pump water comes out. I suppose that could just be pressure from the impeller correct? Is there a way to determine if there is a pump issue?
If bugs made it through the impeller would they not be able to make it the whole way through the system? There was nothing in or around the thermostat. Could there be a clog in the exhaust manifold or elsewhere? Is there a way to check? Is there a way to backflush the entire system? If so what is the proper procedure?
Any other possible causes? There does not appear to be any failed gaskets, oil leaks or anything else. If it were a head gasket or other engine issue I'd think it would run hot consistently instead of intermittently. Help!
Right from the dock she went to 225. I removed the thermostat and she ran cold as expected. 110 on plane and 125 to 150 while trolling depending on my rpms. OK... thermostat right? Not so fast.... after about 2 hours of slow trolling around 800 rpms I notice shes up just a little to 160. Odd since nothing changed (speed/rpms). While staring at the temp guage she goes to 200. So I bump the rpms a little to 1000 (5 mph) and apparenty due to a higher water volume she cools right down. Only now If I go back to 800 rpms the temp will come right back up to 200.
My only 2 guesses are either 1) water pump or 2) more bugs causing a clog beyond the impeller and pump.
Under these circumstances it appears the sea water pump is working properly. Otherwise I'd overheat regardless of rpms correct? If I take the plug off of the top of the water pump water comes out. I suppose that could just be pressure from the impeller correct? Is there a way to determine if there is a pump issue?
If bugs made it through the impeller would they not be able to make it the whole way through the system? There was nothing in or around the thermostat. Could there be a clog in the exhaust manifold or elsewhere? Is there a way to check? Is there a way to backflush the entire system? If so what is the proper procedure?
Any other possible causes? There does not appear to be any failed gaskets, oil leaks or anything else. If it were a head gasket or other engine issue I'd think it would run hot consistently instead of intermittently. Help!
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