Changed impeller. Now temp is running hot. Thermostat problem? Bad impeller?

[dannyual767]

Hello everyone. This is my first post here but I frequent the Stingray boat owners forum. I'm a very mechanically inclined person and I do all of my own wrench turning.

I've done a search on this topic and I found some information but I saw where a lot of people were having issues of engines running too cold.

I just dewinterized my 2004 Stingray 200LX (5.0L carbed Volvo, 220hp) in preparation for summer fun. I replaced the fuel filter and the raw water pump impeller. Oil and filter were changed at the end of the last boating season and I fogged the cylinders. I filled the raw water cooling system with 100% pink, RV antifreeze.

I started up the boat on the garden hose using the Volvo water flush port in the engine compartment. The temp slowly climbed to it's normal 160? mark. Then as I was watching it, the thermostat opened and the temp fell to about 140? and then the thermostat closed and the temp started to rise again. However, this time the temp went up to about 180-190? . After about 2 mins, the temp started to come down a bit but then it started to rise again. When it hit almost 200?, I shut it down.

I checked my garden hose and I was getting good water. Plenty was running out of the outdrive. At this point I wondered if I had installed the impeller correctly. I took the impeller cover back off to confirm the the "fins" were indeed facing the right way. They were so I put everything back together and hooked the garden hose back up.

Upon restarting the engine, it seemed to act like normal running about 160ish. But then, the temp started to climb slowly to 180? and eventually it started to creep up to almost 200 again. I shut it down and took the impeller cover off to make sure that I'd installed the impeller correctly. All appears to be normal. BTW, the old impeller was completely intact so I know that there are no pieces of broken impeller blocking water flow.

Has anyone experienced this before? It seems that it could either be a bad thermostat or possibly something wrong with my new impeller. I need to fix this soon as the big Memorial Day weekend is just around the corner and I've got family coming to town.

Thanks. Danny

 

[tkrfxr]

Re: Changed impeller. Now temp is running hot. Thermostat problem? Bad impeller?

You have to know your engine's cooling system well. Get the manual, and also look at the bottom of this page, to download the Overheat Diagnosis document...the page is in the Volvo Penta information page...

http://forums.iboats.com/showthread.php?p=2360521#post2360521

-Good luck.

 

[cedarjunki]

Re: Changed impeller. Now temp is running hot. Thermostat problem? Bad impeller?

possibly install the impeller in backwards?

 

[dannyual767]

Re: Changed impeller. Now temp is running hot. Thermostat problem? Bad impeller?

You have to know your engine's cooling system well. Get the manual, and also look at the bottom of this page, to download the Overheat Diagnosis document...the page is in the Volvo Penta information page...

http://forums.iboats.com/showthread.php?p=2360521#post2360521

-Good luck.

tkr, I've downloaded several of those tech manuals including the "overheat" manual. I'm going to do some study of them over the next couple of days and see if something jumps out at me.

Thank you for the links to that great information!

 

[dannyual767]

Re: Changed impeller. Now temp is running hot. Thermostat problem? Bad impeller?

possibly install the impeller in backwards?

I installed it just the way I took the original impeller out. It had "Volvo" and number markings on one side and was smooth on the other. The markings were facing toward the crankshaft. I installed the new impeller the same way.

Before I installed it, I looked at it closely and it didn't really appear to be any different one way or the other. One side had markings and the other didn't. I looked at the original impeller and it was the same, however the numbers were different than on the new impeller.

Even though the numbers were different, the impellers looked the same when viewed side by side.

 

[cedarjunki]

Re: Changed impeller. Now temp is running hot. Thermostat problem? Bad impeller?

I installed it just the way I took the original impeller out. It had "Volvo" and number markings on one side and was smooth on the other. The markings were facing toward the crankshaft. I installed the new impeller the same way.

Before I installed it, I looked at it closely and it didn't really appear to be any different one way or the other. One side had markings and the other didn't. I looked at the original impeller and it was the same, however the numbers were different than on the new impeller.

Even though the numbers were different, the impellers looked the same when viewed side by side.

i dont mean upside down. and im not saying you actually did anything wrong either. just throwing out an option which has occurred more than once..
i mean installing the impeller in reverse rotation, which could possibly burn it or rip a flap off when fired up. again its just a thought since its running hot after the new impeller.

 

[gjcombs]

Re: Changed impeller. Now temp is running hot. Thermostat problem? Bad impeller?

Hi,

See my thread for this similar issue:
http://forums.iboats.com/showthread.php?t=392908&highlight=gjcombs+thermostat

Pull the thermostat and test it on your stove and test against what your manual says for running temps.

Even though your thermostat may be rated at 160F, this is where they start to open. It could take another 25F to open fully. With the right conditions (see my thread) the temp could jump up higher than normal.

Make sure your muffs are on all the way completely covering the intake ports.

 

[Don S]

Re: Changed impeller. Now temp is running hot. Thermostat problem? Bad impeller?

If it's a raw water cooled engine, it very well may be the thermostat is sticking after setting all winter. When the engine gets hot, are the exhaust risers still running cool? if so, you can just about bet it's the thermostat.
A raw water cooled engine shouldn't see over 170? even under load, and never 190 to 200?

 

[Hansolo99]

Re: Changed impeller. Now temp is running hot. Thermostat problem? Bad impeller?

You mentioned early on that when you first tried it "The temp slowly climbed to it's normal 160? mark. Then as I was watching it, the thermostat opened and the temp fell to about 140? and then the thermostat closed and the temp started to rise again." Sounds like it is sticking. When replacing a radiator or even hoses on a car it is strongly suggested to replace the thermostat. Take it out and TEST it like mentioned on the stove. You may be surprised......

 

[dannyual767]

Re: Changed impeller. Now temp is running hot. Thermostat problem? Bad impeller?

Hi,

See my thread for this similar issue:
http://forums.iboats.com/showthread.php?t=392908&highlight=gjcombs+thermostat

Pull the thermostat and test it on your stove and test against what your manual says for running temps.

Even though your thermostat may be rated at 160F, this is where they start to open. It could take another 25F to open fully. With the right conditions (see my thread) the temp could jump up higher than normal.

Make sure your muffs are on all the way completely covering the intake ports.

I've got a Volvo engine and it has a freshwater flush port hose inside the engine compartment. I just screw my garden hose directly into this port. No muffs needed .

When I get the thermostat out, I'll inspect it for obvious damage then I'm going to test it along with a brand new thermostat in a pot of hot water with a thermometer.

 

[dannyual767]

Re: Changed impeller. Now temp is running hot. Thermostat problem? Bad impeller?

If it's a raw water cooled engine, it very well may be the thermostat is sticking after setting all winter. When the engine gets hot, are the exhaust risers still running cool? if so, you can just about bet it's the thermostat.
A raw water cooled engine shouldn't see over 170? even under load, and never 190 to 200?

Yes, the risers were running cool. In fact the whole engine just didn't seem to be all that hot. I touched the side of the block and I wasn't worried that it was overheated.

Normally, the engine runs right at 160?F. I've maybe seen it go up to 170? during normal boating but that is it.

 

[dannyual767]

Re: Changed impeller. Now temp is running hot. Thermostat problem? Bad impeller?

Hansolo99, I'm going to look at my impeller installation again tomorrow and I'm probably going to pull the thermostat as well. I'll post info on what I find.


Danny

 

[dannyual767]

Re: Changed impeller. Now temp is running hot. Thermostat problem? Bad impeller?

I pulled the original thermostat (160?) and hung it by a string in a pot of water. I also hung the new thermostat (150?) along with a themometer.

The old thermostat opened up just after the new thermostat so all appears to be well there.

1. I installed the new thermostat and, at the advice of my wife, went ahead and put the original impeller back in the raw water pump. Upon warming up the engine, the thermostat opened and the engine kept a nice 150-160? constant temp.

2. I really wanted to use the brand new impeller. After all, that's why I bought it. I reinstalled the new impeller and then reran the engine. The temp went past 160 and rose to about 180?+ before I shut it down.

3. I decided to put the original back in and be done with it but Murphy's law decided to bite me. Upon restarting the engine, the temp rose all the way up past 190? ! I had been reving the engine up to about 2000rpm. Maybe that's why the temp rose?

4. Since I almost never give up, I reinstalled the new impeller and restarted the engine. I idled it for about 7 or 8 mins and the temp was a steady 160?. After another minute or two, the temp started to nudge up towards 170. I turned the water pressure up a little more and the temp stabilized at 170? for the last 5 mins that I ran the engine. There was no reving the engine. This was all at idle speed. I decided to leave well enough alone!

Each time I exchanged the impeller in the pump, I made sure that the vanes were facing the correct way.

Tomorrow, we are going to put the boat in the water and see how it does. I'm planning on staying real close to the boat ramp until I'm comfortable that the cooling system is doing it's job. I'll report back here tomorrow evening.

 

[Hansolo99]

Re: Changed impeller. Now temp is running hot. Thermostat problem? Bad impeller?

You don't want to run it too long with the hose and muffs. I think you are fine. I think maybe when you revved up the water pressure might have been too low to keep the temp down. After a boat ride be sure to post the update!!! Oh Yeah HAVE FUN OUT THERE!!!

 

[gjcombs]

Re: Changed impeller. Now temp is running hot. Thermostat problem? Bad impeller?

I agree and think you are fine too. I know you will keep an eye on your temp.

I had a similar issue with a marginal temperature. I checked my impeller and all seems fine. I chalk it up to not being in the water and a sticky thermostat. I would not rev the engine about 1500 rpm with only muffs on.

I have not put mine in the water since I changed it. I am confident it will stay in the running temp for mine.

Let us know how your experience goes.

 

[dannyual767]

Re: Changed impeller. Now temp is running hot. Thermostat problem? Bad impeller?

Hans and gjcombs, you guys were right.

It was a beautiful day and we took the boat out. My plan was to stay close to the boat ramp until I was comfortable that the cooling system was operating correctly.

Putting around near the boat dock,the engine warmed up to 160?F and stayed right there. After about 5 mins of a steady 160?, we decided to go for a ride and I pushed the throttle up to about 3000-3200 rpm. We rode for a solid hour and the temp was pretty much on 160? the whole time.

When I slowed down after extended higher speed running, the temp went up to about 170? due to the "hard worked" engine and the lower water flow at idle. Within about two minutes, the temp came back towards 160.

We ran the boat for about 1 1/2 hrs today and not only did the cooling system work great, but the engine ran great as well on last year's stabilized, ethanol gas .

 

[Hansolo99]

Re: Changed impeller. Now temp is running hot. Thermostat problem? Bad impeller?

GREAT glad to hear it!!!!!!!!!!!!!!!!!!

 

[cedarjunki]

Re: Changed impeller. Now temp is running hot. Thermostat problem? Bad impeller?

glad to hear it was ok.... but always better to be safe and question things than be sorry in the end!