Johnson thermostat problem?

[rc3477]

I have a Johnson 1983 115 outboard and have been getting the control box buzzer going off. I checked the head temps at idle and they came up different. When looking at the prop the right two cylinders are running at 120 degrees, while the left two are running at 85 degrees , i have a good tell tale stream. Any help would be appreciated thank you.
ray

 

[HighTrim]

Re: Johnson thermostat problem?

Is the alarm going off when you start the boat, or after a brief interval?

If it sounds after a period of running, and it is not overheating, you will need to test the heat sensors.

 

[emdsapmgr]

Re: Johnson thermostat problem?

Once you get the sensor issue resolve, I'd consider replacing the thermostat on the cold side of the engine (better still, do both.) It must be stuck open, or the pressure relief valve is deformed and may be passing water at idle. For optimal performance and long engine life, the engine should come up to normal operating temps-like the 120 side. FYI, the thermostats should open at 143 degrees.

 

[ezeke]

Re: Johnson thermostat problem?

Check that the temperature switch wires are away from the spark plug wires.

You can get a kit for your thermostats that comes with everything for the overhaul: http://www.iboats.com/mall/partfind..._row=44&keywords=18-3673&**********=412175432

 

[rc3477]

Re: Johnson thermostat problem?

Yes the buzzer goes off after about 15mins of slow running in the harbor. Hightrim by heat sensors do you mean the thermostats?
Thanks for the replies guys
Ray

 

[ezeke]

Re: Johnson thermostat problem?

The sensors are switches connected by tan wires to the main harness. When they sense that the engine has overheated they close and ground the horn, warning to immediately turn the engine off before the engine is damaged.

The temperature switches are imbedded behind the water covers on the cylinder heads at the points where you see the tan wires emerging.

Besides the obvious problem with your stuck thermostat, the V4 engines have four rubber water deflectors in the water passages of the cylinder heads which sometimes move out of place, causing the water not to circulate properly around the cylinder.

 

[rc3477]

Re: Johnson thermostat problem?

thanks for the help. Going to check it out and I'll let you guys know.

 

[rc3477]

Re: Johnson thermostat problem?

so i finally recieved my rebuild kit for the thermostats and went to put them in. Well as we all know rust sucks. All the bolts are a mess. I tried to take one out and it began to make it round. Any hints on how to get these things out its pretty tight in there as I'm sure you guys know.
Thanks
Ray

 

[ezeke]

Re: Johnson thermostat problem?

You need a 6 point socket or box wrench to get a good grip on those bolts.

You can reach the bolts more easily if you drop the rear exhaust cover, located under the lower engine cover. It requires removing 4 screws from the front cover and 2 from inside the lower engine cover.

I've had a few crossflows and am rebuilding one now. I usually drill a pair of access holes from the back through the lower cowl so that I can use a socket straight on to reach the thermostat cover. Then I cover the holes with aluminum repair putty until the next time.