1976 Johnson 115 overheating

[aintmisbehavin]

Waterpump is 1.25 yrs old.

This issue just started a couple weeks ago. Engine will run fine, but anything over 3/4 throttle for more than a couple minutes it will sound the buzzer.

Where are the thermostats located on this engine?
Are they easy to check?
I have a new water pump kit to install, but wanted to check everything while I was at it.

Anything else to check?

thanks

 

[Daviet]

Re: 1976 Johnson 115 overheating

What is the model number for your engine?

 

[iwombat]

Re: 1976 Johnson 115 overheating

At the bottom of the heads are two hoses that lead to the houseing for the single varnatherm (no thermastat on this motor). Do you get spitting out the exhaust relief ports when you run it? If so your vernatherm is working properly. You might want to check the diverters under the heads, or pop off the big hoses to the vernatherm and make sure you're getting good water flow.

 

[aintmisbehavin]

Re: 1976 Johnson 115 overheating

Model number for the engine is 115EL76G.


I am getting the spitting at idle, and a decent stream at speed out of the exhaust ports, even while the buzzer is sounding off.

I was going to try and open where the cooling hoses go, but those bolts are rusted bad. I soaked them with PB Blaster, and I'll try tomorrow.

Till then I am looking for possible places to search for info.

 

[iwombat]

Re: 1976 Johnson 115 overheating

Have you measured the block temp when you get the overheat. It could be as simple as a bad sensor.

 

[aintmisbehavin]

Re: 1976 Johnson 115 overheating

I called the Marina's today to see if they had those "Crayons" that melt at certain temps but no one had them. Might try and borrow a infared temp sensor from work and try it in the water.

If it is the sensor, can I take that out to inspect/clean that prior to heading to the river?

 

[iwombat]

Re: 1976 Johnson 115 overheating

You can try the simple touch test. It's crude but effective. Get the motor up to operating temps and hold your hand on the top of the block. You should be able to count:

1

2

3

ouch.

 

[aintmisbehavin]

Re: 1976 Johnson 115 overheating

1

2

3

ouch.

Roger that. I tried that Saturday out on the river. It was hot to the touch but was able to withstand a few seconds as you suggest, plus OAT was 90 or so.

 

[iwombat]

Re: 1976 Johnson 115 overheating

It's most likely just a sensor then. I'd still hit it with the infrared. Could be the vernatherm is opening a tad too late. A new sensor will run you $50 or so. Spendy lil' critters.

 

[aintmisbehavin]

Re: 1976 Johnson 115 overheating

Do you know the process for removing the temp sensor? Where are they normally located on the block? Is there an Ohm test for the sensor, or boiling it to see when it triggers?

 

[aintmisbehavin]

Re: 1976 Johnson 115 overheating

I was able to drop the lower unit today and look at the water pump, nothing looks out of the ordinary. The impeller is still in excellent condition. And the housing looks to be in order.

What else should I look for prior to reinstall while the LU is down?

 

[iwombat]

Re: 1976 Johnson 115 overheating

Temp sensor is on the head. I think that year only had one - located on the starboard head. You'll see a little brown wire sticking out. There's a connector inside the rubber sleve a few inches up. It's a lot easier (necessary?) if you remove the head cover first. Pop the old one out, and put the new one in. Your overheat horn is, at least, waiting a little while beofore going off, right? By that I mean there's not a dead short in the sender wire is there?

 

[aintmisbehavin]

Re: 1976 Johnson 115 overheating

Temp sensor is on the head. I think that year only had one - located on the starboard head. You'll see a little brown wire sticking out. There's a connector inside the rubber sleve a few inches up. It's a lot easier (necessary?) if you remove the head cover first. Pop the old one out, and put the new one in. Your overheat horn is, at least, waiting a little while beofore going off, right? By that I mean there's not a dead short in the sender wire is there?

Temp sensor is on the head. I think that year only had one - located on the starboard head. Yep, on right (I'm a airdale) side

if you remove the head cover first If I do this, what kind of gaskets do I need to replace by doing so?

connector inside the rubber sleve Haven't messed with the sleeve, I'm guessing its a quick disconnect? but haven't touched it yet.

horn is, at least, waiting a little while beofore going off, rightHorn will not sound off until it is ran at WOT for a couple of minutes.


Not trying to look or sound like an a_hole by replying this way, thought it may be easier to read

 

[aintmisbehavin]

Re: 1976 Johnson 115 overheating

I dropped the lower unit to look at the water impeller. The impeller which is 1.5 yrs old looks almost new. Had another impeller kit, so replaced everything this evening.
While the LU is down I took my air compressor and blew 90psi into the water jackets to see where or how my flow is going.

I took both upper head coolant hoses off and thus did the following:

Blow IN Left Top = Flow OUT= Right Bottom
if I plug RB= Flow out Right Top

Blow IN Right Top= Flow OUT right bottom
plug right bottom= flow out Left Top

Blow IN Left Bottom= it seems to stop and not flow out anywhere, is this a problem or is this normal op's since the thermostat isn't open in this situation?

sorry if this is a little erratic, but a couple beers into it, it makes sense to me.

 

[95cajun]

Re: 1976 Johnson 115 overheating

what about the bypass valves? I thought that at 3 grand or so the pop offs allowed full water flow? Still learning here?

 

[95cajun]

Re: 1976 Johnson 115 overheating

I'm Learning as I go here, check the obvious first, check your oil fuel mixture! Don't let anyone tell you that mixture, spark, timing will not affect the temp of your motor. If your in doubt about your fuel mixture of if it's oil injected have the system checked! Add more oil to your gas, I know that carbon build up is an issue but overheating is much more serious! I would rather replace plugs than a motor.