Johnson 115 1990 - water temp gauge goes where?

[Klink]

I want to install a water temperature gauge on a 1990 Johnson 115 I just bought. Where does the sender tap into? I don't see any threads for a sender. What kind of sender does it use, in the water or touching the outside?

(PS- I'm also going to install a water pressure gauge, which I'll just T into the indicator pee hose.)​

 

[boobie]

Re: Johnson 115 1990 - water temp gauge goes where?

Whatever water temp gauge you get there should be instructions with it as to where to install it. There are different types.

 

[toddschubert]

Re: Johnson 115 1990 - water temp gauge goes where?

I installed one on the center on the thermostat housing using that center bolt and some grinding down (rigging) of the bracket that came with gauge. Works like a charm but gives you only a composite temp from both heads which on mine is the same temp of each individual head. a rise in temp will show on gauge then you can further investigate which head/cyl it is.

 

[Klink]

Re: Johnson 115 1990 - water temp gauge goes where?

I installed one on the center on the thermostat housing using that center bolt and some grinding down (rigging) of the bracket that came with gauge. Works like a charm but gives you only a composite temp from both heads which on mine is the same temp of each individual head. a rise in temp will show on gauge then you can further investigate which head/cyl it is.

I don't see anything resembling a thermostat housing. I see a Transistor (?) with a wire, coming out of two of the heads, on the #2 and #3 , but no thermostat housing.

 

[kjdunne]

Re: Johnson 115 1990 - water temp gauge goes where?

Look below the cylinder heads, in the center, under the bubbleback. It'll have rubber water hoses attached to it.

 

[emdsapmgr]

Re: Johnson 115 1990 - water temp gauge goes where?

Normally, the flat tip of the sender should lie flat against the head. You may have to make a "Z" bracket (mount) which will hold the sender in place. That's the typical mounting for a V engine. Problem is that it only measures the temp of that one head. Since both heads are independently cooled, you run a risk that the other head could run hot and you'd not know it till you got a hot horn warning. That's why the factory put the overheat switches in each head. Mounting the sender on one head still provides a solid indication of the general temp of the powerhead. kjdunne's mounting location offers an interesting solution.

 

[Klink]

Re: Johnson 115 1990 - water temp gauge goes where?

Normally, the flat tip of the sender should lie flat against the head. You may have to make a "Z" bracket (mount) which will hold the sender in place. That's the typical mounting for a V engine. Problem is that it only measures the temp of that one head. Since both heads are independently cooled, you run a risk that the other head could run hot and you'd not know it till you got a hot horn warning. That's why the factory put the overheat switches in each head. Mounting the sender on one head still provides a solid indication of the general temp of the powerhead....

Another solution to the two heads problem could be to mount one sender on each head with the Z brackets, and have a switch to the gauge? Overkill if the overheat switch alarm system is working?

re:kjdunne's mounting location offers an interesting solution

Could that location be affected by the thermostat when it is warming up? I don't see a cooling system flow diagram in my manual. I would think the best location would be where it has the hardest time getting water, the top of the heads?​

 

[Klink]

Re: Johnson 115 1990 - water temp gauge goes where?

Found this water flow chart in the manual:


The water flows up the middle of both heads and out down the outsides.

I think this means that the thermostat housing has incoming ocean/lake cool water flowing through it, and the hottest water flowing out through it from the top. This is what I meant when I asked the question above about the thermostat housing location. The hot and cold water on the thermostat housing could compromise the accuracy of the temperature readings? Thoughts?

By the way, I can see now the reason why OMC located the temperature switches where they did, it is where the water will get the hottest on both heads.​

 

[emdsapmgr]

Re: Johnson 115 1990 - water temp gauge goes where?

The thermostat housing is at the back end of the cooling system. The stats open so that water can exit the block back into the midsection.