gt 150 overheating

[icandoit]

my 1990 gt 150 will overheat and trip the alarm when it is run over 3500 rpm's. I have changed the entire water pump assembly and it is pumping more water out the pee hole than before but my problem is still the same. I know the engine is signaling an overheat because if I disconnect the heat sensor on the port side the horn silences. My engine does have VRO.<br /><br />Is there an upgrade to the water pumps on my year model like drilling holes in the block? I read this in a previous post but for a different engine.<br /><br />Does this engine have a thermostat and where in the heck would it be and how hard is it to get to?

 

[Solittle]

Re: gt 150 overheating

The manual that you should buy for this engine will show you where the thermostats are and how to replace them. Also check the Suggestions for new poaters below and I have found that the Search function at this Web site has a ton of tips from folks who have have already done this.

 

[icandoit]

Re: gt 150 overheating

I had already searched and found no info on my make and model and that is how i knew about the heat sensor in the first place.<br /><br />I will get a manual since i still don't know where the thermostats are.<br /><br />Thanks for the help.<br /><br />I thought I was following the rules

 

[clanton]

Re: gt 150 overheating

Did you replace the complete water pump with a OEM kit? Thermostats are located in top of each head. Cant remember if this is a 90 degree or 60 degree engine. If it is a 90 degree crossflow engine, high speed over heat can be caused by water deflectors under cylinder head and o-ring under inpeller cup.

 

[icandoit]

Re: gt 150 overheating

I think it is a 90 degree. how would i know? <br />After I get a manual i'll change the thermostats and give it a test run.<br /><br />thanks a lot

 

[BKool68]

Re: gt 150 overheating

90 degree is the older wide style block. The 60 degree block is narrower.

 

[seahorse5]

Re: gt 150 overheating

The 60 degree block came out in '91.<br /><br />Remove the diaphragms and white pressure relief valves and check to see if they are sticking inside the rubber seal ring, when you replace the thermostats. Sticking causes overheating at higher speeds. You could also have the problems with deflectors, as mentioned, or a build up inside the cylinder-head water covers that restrict the outflow of cooling water.

 

[Dhadley]

Re: gt 150 overheating

Just a thought, icandoit, but it may help avoid further confusion as to which motor you really have if you post the model number. I know a '90 is a crossflow and a '91 is a 60 degree looper but without looking at yours its hard to tell. The motors are totally different and the answers will be less decieving if we know what you have.<br /><br />Good luck!

 

[icandoit]

Re: gt 150 overheating

The model no. is J150STLESB and is a 1990 model which should make it a 90 degree crossfire. After looking at the head arangement i beleieve it is a 90 degree motor.<br /><br />The water pump that i replaced was an OMC original part 0151594 or something close to that number.<br /><br />I have pulled the water pump and checked the o-ring under the impeller cup it looks to be fine.<br /><br />I will change the thermostats when they come in and check the diaphragms at that time.<br /><br />thanks again

 

[icandoit]

Re: gt 150 overheating

I ran it for a test run today after changing the thermostats and replacing the diaphragm on the pressure relief valve. The relief valves did appear to be sticking.<br /><br />The engine ran at high speed without overheating and would not melt a 175 F temp. stick.<br /><br />Thanks very much for the expertize in helping me solve my problem one step at a time.