225 Johnson thermostat question

[klauricella]

Just purchased a 1989 225 Johnson and had to replace a piston got everything back together and went to replace thermostat diaphragm. Pulled cover and there is a spring and no diaphragm. I have service manual it shows a diaphragm and gasket kit for the motor had diaphragms. Is this ok? Thanks

 

[Dhadley]

Re: 225 Johnson thermostat question

The 1986 -92 motors used the water controlled valve (just in back of the throttle arm) and the 93 & newer motors didn't. The 93 & newer used a spring & gasket on the t-stat assembly, the 92 & older used a diaphram and no gasket.

Is the water control valve still there?

 

[klauricella]

Re: 225 Johnson thermostat question

Valve is still there but disconnected. Should I get original thermostats or is it ok?

 

[Dhadley]

Re: 225 Johnson thermostat question

Nope, it's OK. Someone has upgraded the system (which I would too). There's something else I'm curious about but I think you'll be OK.

The 89 should be an open deck block - with the heads off you can see the water passages. The cylinders are not connected to the side of the block. Is yours like that? Or is it a closed deck (with the head off there is aluminum from the cylinders to the outside of the block, like a Chevrolet block)?

 

[klauricella]

Re: 225 Johnson thermostat question

It is open you can see between cylinders and block. Thanks for the answers, also what year thermostat kit would I need to order to replace gaskets.
Thanks again.

 

[Dhadley]

Re: 225 Johnson thermostat question

The gasket from a 93 200/225 will work. The 3 cylinder 70's are the same too I believe.

 

[gregr1971]

Re: 225 Johnson thermostat question

Dhadley, can you please explain the procedure, and parts needed to update the cooling system?
i have a '90 200hp, and want to update it, i use it offshore and ANY extra insurance is a plus!!
Thanks.

 

[Dhadley]

Re: 225 Johnson thermostat question

On a 1986 to 92 carb'd 90* V6 looper you can use the t-stat cap, gasket and spring from a 93 & newer 200/225. Remove the diaphram from the vernatherm and reinstall with the new cap, gasket & spring. Be sure to get the cap and spring from the same year. There are a couple different caps and they'll all work, just consider the cap and spring a set.

Once you do that you can eliminate the throttle controlled water valve and a bunch of hoses. You'll have to plug the hose from the adaptor to the valve but you can still leave the T for the water pressure gauge in the line.

 

[Dhadley]

Re: 225 Johnson thermostat question

BTW - either system works well, the 93 & newer system is much cleaner looking.

 

[gregr1971]

Re: 225 Johnson thermostat question

what actually is the purpose of that valve?

 

[Dhadley]

Re: 225 Johnson thermostat question

To control water pressure to the backside of the diaphram so the vernatherm will operate properly. Once the diaphram is removed the valve is no longer needed.