One head hot the other head cold???

[sunbird1]

I took the boat out on saturday and the engine ran great. I noticed the temp guage was reading around 100 degrees so I figured all was well. Got back to the dock and flushed the engine on the muffs and the water coming out of the telltale was cold. I took the cover off and felt the heads. The port head was cold and the starboard head was warm. Engine is 1990 Johnson 120 VRO. What would cause this? Is it as simple as a stuck thermostat? What else should I check?<br />thanks

 

[marinegrh]

Re: One head hot the other head cold???

id start with the stats, like you said, if that does not solve you temp issue, you may consider a water pump job next, should be done annually anyway, if you still have a heat problem, pulling the heads and water covers and cleaning would be your next step, also replace the flow deflectors while in there, make sure to surface the heads and covers before re install so you get no leaks ,, aquire a service manual befor eyou attempt these repairs, it always helps<br /><br />keep us infoed

 

[sunbird1]

Re: One head hot the other head cold???

Thanks for confirming my thoughts. I did have the water pump done in the beginning of the season and it has been pumping fine so hopefully that's not the problem. If the stats don't do it, I'll start going through my manual.

 

[sunbird1]

Re: One head hot the other head cold???

One quick question, can I do any damage to the engine by running it this way with one head not getting warm? I would think it can't be good but a friend at work said it is no big deal. Any thoughts? I will absolutely fix this problem but I would like to know if this guy is right or wrong.

 

[Solittle]

Re: One head hot the other head cold???

You may have a problem and it is not due to the motor running hot. After you start your motor and let it warm up you should be able to put your fingers on either head for only 5-8 seconds before it gets too hot to touch. If either head is cold your motor is running too cold. I think your motor should run at about 140-145 degrees. You can get temperature sticks to confirm.<br /><br />I would suspect that someone removed your thermostats.

 

[rodbolt]

Re: One head hot the other head cold???

hello<br /> running an OMC looper cold can cause all kinds of problems. excessive smoke, carbon.it may cause the quick start to try to engage at low speed causing an unstable idle. the T stats are easy enough to change. good luck and keep us posted

 

[93bronco]

Re: One head hot the other head cold???

check your tstats, make sure that the ones you take out arent hollow in the inside.<br />if they are someone removed the vernatherm, possibly to cover up an overheating issue.<br />-<br />unless you are the original owner.<br />-<br />but if that is not the case, i would definitly change out head gaskets just to be sure.<br />i know because it happened to me.

 

[sunbird1]

Re: One head hot the other head cold???

Thanks guys, I will definitely check and change the thermostats. I know they are in the engine because I changed them the middle of last season and it has run great until now. The boat actually sat in my driveway for past three weeks without use, maybe that had something to do with it - family and new baby stuff to do. Before this I was using it atleast once almost every weekend.<br /><br />I'll let you know what I find.

 

[Solittle]

Re: One head hot the other head cold???

Sitting idle for three weeks should not be part of the equation.

 

[sunbird1]

Re: One head hot the other head cold???

Update: I replaced both thermostats and gaskets on Friday, ran it on the muffs and everthing was fine. Took the boat out yesterday and when I was flushing the engine I noticed that the head that was hot is cold and the head that was cold is hot. Now I have no idea what to check. Any ideas would be appreciated. Thanks in advance.

 

[sunbird1]

Re: One head hot the other head cold???

Just to clarify the gaskets I changed were for the thermostats and not the head gaskets.

 

[sunbird1]

Re: One head hot the other head cold???

BUMP^