Overheating

[stuartmcnair]

Here is the situation:

'89 Prostar 190 351W. When running hard temp stays around 160. If I stop it rises to alarm and I rev the motor in neutral and it drops back down.

So far, I have put in a new impeller, new 143 degree thermostat and I had to change the drive belt as the old one was turning to powder and the engine was squealing. I also checked the screen on the transmission cooler and it had no debris in it.

I am not sure if the new belt is tight enough as I have never changed one before. Could it be as simple as tightening the belt more?

I was not having the overheating problem until last weekend when I noticed the belt began to squeal. There is no shredded impeller debris in the engine and water seems to move through fine.

I did notice that the hose on the bottom left side of the thermostat housing (large hose) was a little soft. Probably going to replace that hose as well as the two that go from the thermostat housing to the manifolds just to make sure all the hoses are good.

[JimN]

Here is the situation:

'89 Prostar 190 351W. When running hard temp stays around 160. If I stop it rises to alarm and I rev the motor in neutral and it drops back down.

So far, I have put in a new impeller, new 143 degree thermostat and I had to change the drive belt as the old one was turning to powder and the engine was squealing. I also checked the screen on the transmission cooler and it had no debris in it.

I am not sure if the new belt is tight enough as I have never changed one before. Could it be as simple as tightening the belt more?

I was not having the overheating problem until last weekend when I noticed the belt began to squeal. There is no shredded impeller debris in the engine and water seems to move through fine.

I did notice that the hose on the bottom left side of the thermostat housing (large hose) was a little soft. Probably going to replace that hose as well as the two that go from the thermostat housing to the manifolds just to make sure all the hoses are good.

If you ever had vanes come off of the impeller, remove the thermostat housing and look in the little hole. Now, get your mind out of the gutter. The hole is about as huge as a pencil (I'm not sure how much can flow through it but hey, it's their design) and I have seen pieces stuck in it.

Also, and because it happened to me, make sure the water pump housing is installed correctly. The housing will get really hot if it isn't so if you touch it, only tap your fingers on it.

[nmcjr]

Did this problem exist before you changed the impeller, thermostat and belt? I assume so, but wanted to confirm.

[stuartmcnair]

I changed the impeller at the beginning of the season...pulled out a perfectly good one and replaced it with a new one. As long as I have owned it I have not shredded one and it has never run hot.

I will pull that impeller this weekend and check that hole. Just for grins I will put another new one in. I will also to a test from Skidim to verify it is pumping enough water to try and isolate the problem to before or after the impeller then before or after the thermostat.

Really frustrating.

[TMCNo1]

I changed the impeller at the beginning of the season...pulled out a perfectly good one and replaced it with a new one. As long as I have owned it I have not shredded one and it has never run hot.

I will pull that impeller this weekend and check that hole. Just for grins I will put another new one in. I will also to a test from Skidim to verify it is pumping enough water to try and isolate the problem to before or after the impeller then before or after the thermostat.

Really frustrating.

Mine will run 145 to 155 or 160 depending on the water temp of the lake and season and if I shut it down after a hard run on a hot day, it will occasionally heat soak to about 200 and can go to crank it and the alarm will barely sound and when idling it will drop back down to 155 or so in a couple minutes.

[mark g]

i had the same problem as you described to the letter, mine ended up the thermostat faulty, i know you changed it out but i would check it is working, easy enough in a pan of water, suppose you could have picked up a faulty one, highly unlikely but worth a try.

[JimN]

I changed the impeller at the beginning of the season...pulled out a perfectly good one and replaced it with a new one. As long as I have owned it I have not shredded one and it has never run hot.

I will pull that impeller this weekend and check that hole. Just for grins I will put another new one in. I will also to a test from Skidim to verify it is pumping enough water to try and isolate the problem to before or after the impeller then before or after the thermostat.

Really frustrating.

You might want to backflush the raw water pickup hose, just in case it sucked up a bag or something.

[nmcjr]

Any chance the thermostat is upside down? Of course if the problem existed before the therm change, then probably not, but just thought i might throw that out there--not even sure it would cause the symtoms you indicate, but just an idea because it seems like you have covered your bases.

[stuartmcnair]

Any chance the thermostat is upside down? Of course if the problem existed before the therm change, then probably not, but just thought i might throw that out there--not even sure it would cause the symtoms you indicate, but just an idea because it seems like you have covered your bases.

Two new thermostats from two different sources acting the exact same way...I hope that is not it...I am going to test the pickup rate this weekend. Supposed to fill a five gallon bucket in fifteen seconds. Once I do that I will know more. If it does not fill I will begin by replacing...everything. Hoses, pumps, transmission cooler...you can never do enough parts replacing. :)

[corey]

Two other ideas on what could be causing this.

1. Worn water pump bearing
2. Bad impellar, its rare but Ive seen the metal inards seperate from the rubber outer causing the impellar to not turn even though everything else appears fine.

[nmcjr]

I wouldn't replace parts just yet. I think it is more likely a blockage, or an otherwise simple problem, such as those mentioned above.

Also check the inlet and outlet of the raw water pump. I once had a blockage there that was not obvious at first. I suggest pulling the impeller and using a mirror to look inside the tubes.

[austinMC]

Loose, even a little bit, connections at the raw water filter will cause that problem. Try taking the barbed connectors off the water filter and teflon taping them and retightening. Also make sure the rubber o-ring in he water filter housing is present and in good condition. I had the same heating issue in my PS197 and that fixed it right away.

[ahhudgins]

The one thing you mentioned that concerns me is the belt noise and "turning to powder". Your temperature is staying normal at speed because the water is being pushed into the pickup. At idle, the impeller does ALL the work. When you take the pump housing off of the motor you should be able to rotate the pulley by hand very easily and you can feel and hear the vanes as they rotate. If your bearing is bad it will be hard to turn which would eat up your belt. The opposite hold true as well, you should be able to take the hose off of the transmission cooler (output side going to the impeller) and stick it in a 5 gallon bucket of water. Start the motor up and it should suck the water out in about 10-15 seconds. I've owned 3 different MCs and they pull the same amount of water.

[stuartmcnair]

ok, a follow up to this post...I finally was able to get this fixed and it turned out to be pretty simple. Everything checked out with all the parts being OK. A check of everything again today and noticed that the clamp was loose on the raw water hose into the impeller housing. That was allowing air into the system which was more of a problem at idle.

Tightened everything up and the temp dropped below 160.

[mayo93prostar]

good job stu. glad you got it fixed. another suggestion for future reference is to run it without a thermostat to help isolate the problem.

[stuartmcnair]

I had tried that with the same result...on the plus side I now have a spare thermostat, impeller and drive belt

[trickskier]

Gald to hear that you found the problem.................Now get out there on the H2o!!! :D