1972 Johnson 20 hp Leaking

[amvaneyk]

Thanks to everyone on here I finally got it to crank!! Runs really well, I was just running it in a barrel so i left it in neutral. However I have a small stream of water shooting out of the top. (Circled in the pictures below). Can someone help me with this? What do I need to do, what parts do I need, is this a pretty straight forward fix. Thanks, The red box shows where its leaking.

 

[Van Wildonher]

Re: 1972 Johnson 20 hp Leaking

Looks to me like you just need a new gasket...

 

[cajuncook1]

Re: 1972 Johnson 20 hp Leaking

Your thermostat cover gasket is leaking....easy fix. Just replace the gasket and torque the bolts to 96 to 120 inch pounds (look carefully inch pounds not foot pounds) Also make sure the cylinder head screw are torqued as well, someone could have removed it and not retorque them properly. (The discoloration of the cylinder head indicates at some point it may have overheated.) Please be sure that the water pump is working and expelling water out of the exhaust relief port about midway down the leg in the back. Check the temp of the head while it is running...should not get more that 160 degree F. (Use a digital laser thermometer on the side of the cylinders.)

Here is a breakdown of the cylinder head and the thermostat. Look at part number #17. Before you order a new gasket, make sure that the thermostat (part # 19) is good. Check out the diagram.

http://www.boats.net/parts/search/BRP/JOHNSON/1972/20R72R 1972/CYLINDER & CRANKCASE/parts.html


Here is a parts breakdown of your motor. click the link.

http://www.boats.net/parts/search/BRP/JOHNSON/1972/20R72R 1972/parts.html

Good luck

 

[amvaneyk]

Re: 1972 Johnson 20 hp Leaking

Can i check if my thermostat is good by just looking at it??

 

[cajuncook1]

Re: 1972 Johnson 20 hp Leaking

Here is quote from one of our very experienced members regarding thermostats.


" ezeke
Supreme Mariner

Testing thermostat

Test your thermostats in a heating pan of water with your meat thermometer in the water. The thermostats are usually either 105 or 143 degrees as marked on the thermostats, though you may need a magnifying glass to see it. You will see them open and can verify the temp at that time with the thermometer. More than half the time you find it isn't the thermostat or vernatherm, but all the accumulated junk in the thermostat housing that causes the problem. Some motors have problems with the seats for the thermostats as well."

Hope that helps you out!!


Check your PM (private message box)

 

[amvaneyk]

Re: 1972 Johnson 20 hp Leaking

I got one of those laser thermometers. Can someone walk me through the process of checking the temp. I am just running it in a trash can of water right now only leaving it in neutral. I just keep the hose running to make sure the water level always stays full. There is sufficient water coming out of the pee hole.

I ran it in neutral just for about ten minutes last week and it looks like there is a little bit of oil around the block. (I was looking on the johnson site and it's a little oily between the CYLINDER & C' CASE ASSY). Is this typical of an old motor or what should I do.

 

[cajuncook1]

Re: 1972 Johnson 20 hp Leaking

Here is a link to a member BeTheKing youtube site. (check out some of his other video....he is pretty informative). In the video he displays using a digital thermometer.

http://www.youtube.com/watch?v=ousjnSl1u84

He is taking the temps on the side of the motor about an inch or two behind the cylinder head. (along the cylinder wall inside of the motor).

Your temps should be less than 160 and should maintain around 130 to upper 140's at idle after it has warmed up.

Hope this helps.