Johnson 112VR - Thermostat Gone Bad?

[gravysandwich]

Changed the water pump in my 1996 Johnson 112VR about a month ago. I have been out several times since then, and the tell tale has been very strong.

Put the muffs on it today in the driveway and thought that the stream didn't look very strong, even when I revved up to 2000 rpm's. The stream on this motor is always lukewarm at best, and today it was hot to the touch ( too hot to leave my hand under it). Moments later, the overheat alarm went off and I shut it down instantly. There was no obstruction in the water tube.

The thermostats were last changed in 2002. Can a thermostat not opening result in reduced flow from the tell tale? I used and OMC water pump and would be surprised if that was the problem. Do I have a thermostat or a water pump problem, based on my description?

Thanks in advance everyone.

(And BTW, I have heard that the thermostat replacement on this motor is no fun at all)

Gravysandwich

 

[oldcatamount]

Re: Johnson 112VR - Thermostat Gone Bad?

It sounds like the thermostats to me, however, when you run an outboard on muffs, you may not be getting the water volume the motor needs to run cool, espeacially with a motor of that much horsepower. If it runs cool when in the water and pushing the boat, it's running correctly. You can check the thermostats if you like. Take them out and put them in a sauce pan on the stove, heat the water to 140 degrees (or so) and watch for them to open. Open=good, unopen=bad.

 

[gravysandwich]

Re: Johnson 112VR - Thermostat Gone Bad?

Thanks for your comments and help.

From what I have read and heard, it is such a chore to replace the thermostats on this motor, if I go to the trouble to pull them, I am definitely going to finish the job.

I am still uncertain about the pressure of the tell tale and why it wasn't as strong as normal. Shouldn't the water pressure remain constant with or without the stats open, at least initially?

I am going to try it again on the muffs, check the hose pressure, and report back.

Gravysandwich

 

[oldcatamount]

Re: Johnson 112VR - Thermostat Gone Bad?

If you can put a trash can under the motor and fill it with water, that would be a better test than muffs. Also, when running the motor on muffs, don't rev it up, that's likely to heat it in a hurry not to mention damaging other internal parts.

 

[gravysandwich]

Re: Johnson 112VR - Thermostat Gone Bad?

Cat,

I stuck the earmuffs on the motor and fired it again and it peed beautifully. I don't think in the ten years that I have had this boat that I have ever put the muffs on incorrectly, but I think that is exactly what happened this time.

Anyhow, no harm done. It started up right away, ran smooth, and the stream was strong and cool (like normal). The first time, the engine just didn't have enough water to cool it properly. I might invest in a better pair of muffs.

I know that the stats will crap out on me one day, but I'm glad it wasn't today.

Thanks again.

Gravysandwich