Weird Thermostat reading

[thundercraft177]

1987 OMC 4.3 262 sterndrive- I took the boat out today and found it got hot up towards 220 so brought it back in. Got home hooked up and ran and treated my cooling system with salt terminator. Temp looks good for about 15 minutes then starts getting warm I varified the water was comming out the exhaust so I know I have flow and it was a good flow. I get up in the boat and squeez the main hose (from the water pump to the thermosate housing). She cools right off. First i think well I had a bad air pocket. Nope heats up again about 2 minutes later. As long as I squezz this hose when it starts to get warm (180-190) it cools right back down. I installed a new water pump and pully with a new thermostat housing and thermostat. I have blown air into the intakes of the exhaust where the water goes in and plan on doing it again. But before I do, I would like to know if there is something else I could do. I have heard of back flushing but unsure of how to do it and my manual doesn't say anything about it.
Other items replaced
Complete upper stern drive from crowleymarine
(old one seized due to no oil in it)
new alternator
new battery
new plugs,wires,cap,points
new coil
new water seperator
new belts

 

[Reel Poor]

Re: Weird Thermostat reading

Have you replaced the raw water pump ? If not you should.

 

[thundercraft177]

Still getting a Weird Thermostat reading 4.3 OMC

Still getting a Weird Thermostat reading 4.3 OMC

Yes the upper unit came complete and replaced the old unit. All shows well have water flow and coming back out the exhaust port. Noticed when I pump the main line from water pump housing to thermostat it cools back off. So on labor day the local shop was open and I went and got a new thermostat and gasket replaced and heats up slower but still gets hot and cools when I pump the line. Should I be going towards cooling lines (which look okay) or the fact that I have a new belt on the alternator and it has a new alternator and with the tension adjustment the top bot that you tighten is almost as hihg as it can go like as if the belt is too big.

Please help!!!:/

 

[Gary H NC]

Re: Weird Thermostat reading

I don't see how squeezing the hose could make that big of difference.
As long as the belt on the waterpump is turning ok it doesn't need to be really tight.
If it was me i would pull the impeller cover off just to check it out.You never know,it could have been defective.Plus with the cover off you can backflush water down the large hose that goes to the T-stat housing.
Have you ever started it without the muffs on?
Also with the boat in the water(not on muffs) you can check flow by removing the large hose from the T-stat housing.Holding it upright you should get about a 2 inch high stream of water with engine at idle.
Do both exhuast manifolds get about the same temp?

Also you are running a 160 degree thermostat?

 

[thundercraft177]

Re: Weird Thermostat reading

I was told by a friend that I need to just take it out and run it, that I might have a air pocket. I told him it takes about 20-25 minutes to heat up out of water with muffs on and then starts to over heat and as soon as I pulse the main line it cools off. Should I test run it out of water and crack the main line to let out air or just run it in the water and see how she does???

 

[Gary H NC]

Re: Weird Thermostat reading

If the impeller is working properly and nothing is restricted it will push out any air in the system.
Pull the impeller cover and inspect it.It could have been installed with the fins the wrong way.
I have had brand new impellers come apart.

Any overheat problem should be fixed before you end up having to change head gaskets and fixing all the other damage.

 

[thundercraft177]

Re: Weird Thermostat reading

Are you saying the impeller on the stern drive. Or the impeller on the water pump on the engine?

 

[Gary H NC]

Re: Weird Thermostat reading

On the stern drive.

 

[thundercraft177]

Re: Weird Thermostat reading

Well I am getting ready to go do a test run. I checked it all and it is all fine. It still gets hot but only if I sit and idle with muffs for 20-30 minutes. I have some pics and am going to try and post them.

 

[Gary H NC]

Re: Weird Thermostat reading

Pics not working here, you have to upload them to a site like photobucket then post the url..

good luck on your test run!

 

[thundercraft177]

Re: Weird Thermostat reading

Heres the pictures at yahoo
http://pg.photos.yahoo.com/ph/superyellow7/album?.dir=/4b7fre2

 

[Gary H NC]

Re: Weird Thermostat reading

How did the test run go?