72 25hp johnson water circulation

[Boat-ryder]

I have a question about the water circulation.i just bought this motor and im having problems with water not circulating.i replaced the impeller and i wanted to check the thermostat as well.my question is if the thermostat was stuck would water still circulate in my lower unit and not the cylinders or does this motor not have a bypass so if its stuck water will not circulate at all? sorry if thats hard to understand.basically do outboards this old have a water bypass around the thermostat? thanks

 

[ADK_Boater]

Re: 72 25hp johnson water circulation

Firstly, water will "circulate" with the thermostat closed. That is why water "pees" out your tell-tale hole.
But, it will not circulate through your entire water jacket and thus will not properly cool your engine when it exceeds the temp that your t-stat pops open at.

So you can test your thermostat in a pot of hot water by suspending it from thin wire and using a thermometer in the water to see if it pops open at the proper temp.
Search for it on youtube. there are videos.

 

[Beek14]

Re: 72 25hp johnson water circulation

Have you checked that something isn't plugging the flow of the water? Any signs of corrosion or does this outboard appear to have been run in salt water? A piece of the old impeller could be plugging the flow or many other things..

 

[Boat-ryder]

Re: 72 25hp johnson water circulation

well the thermostat is working fine. i just got the lower back on today and i gotta say how the shift rod goes on is a terrible design.im guna run it soon and see if the impeller fixed the problem.if not there has to be a blockage somewhere like you said.thanks for the help