1970 Johnson 40hp coming back to life starting with water pump.

[broncojeff78]

Hi everybody. I have a 1970 40hp Johnson that I am fixing up. I originally tested it just to see if it would run before I started to fix it up. I put it in a barrel of water deep enough to cover the water intakes and started it up. No water came out of the upper exhaust hole and the engine ran for a couple minutes and the high temp light came on so I shut it down. I had read that little to no water would come out until the thermostat opened but nothing seemed to happen. I replaced the water pump impeller along with some seals and o-rings and have it back together. The old impeller was worn out but looked as if it may have been able to pump water but not sure. Would it be a good idea to remove the thermostat and test it or do they normally not fail? Can I test the thermostat in hot water? I want to get this squared away before I move on to the other systems. I did fail to mention that this motor likely hasn't been run for 10 years or more. I plan on rebuilding the carb, replacing the fuel lines and replacing the entire ignition system. Is there any other things that I should check and or replace on these old engines? Thanks for the help!

 

[tx1961whaler]

Re: 1970 Johnson 40hp coming back to life starting with water pump.

The lower unit needs to be submerged deep in a barrel in order to pump water. Raise the water level to right below the exhaust port and see what happens.

 

[broncojeff78]

Re: 1970 Johnson 40hp coming back to life starting with water pump.

No kidding, I didnt know it would have to be that deep. I thought if the intakes were submerged it would work. Guess I will have to find a bigger barrell.

 

[tx1961whaler]

Re: 1970 Johnson 40hp coming back to life starting with water pump.

It won't self-prime very well at all, so the water has to be up at a level even or over the top if where the pump sits which is a few inches above the anti-ventilation plate. It helps to be even higher than that with all of the swirling and bubbling that happens in the barrel.
I use a regular old-school metal trash can the pretty well goes up to the transom mount.

 

[broncojeff78]

Re: 1970 Johnson 40hp coming back to life starting with water pump.

Well I got a bigger trash can, filled it up and it worked perfectly. Seemed to pump water as it should for what little time I could get it to run so on to the carb, fuel pump and points. All thats left is everything!

 

[broncojeff78]

Re: 1970 Johnson 40hp coming back to life starting with water pump.

Well I finally got the boat in the water and it sure was worth doing all the work to that old motor. After a minor low speed needle adjustment the motor was running like a sewing machine. Thanks to this site and an original repair manual I replaced/rebuilt all the systems including the carb, fuel pump, points, coils, water pump and fuel lines. The 14ft fiberglass boat only topped out at 22 mph and I thought it would go a little faster but I didnt buy it as a speed boat anyway. All in all its a fun family boat and we even did a little tubing with it and it pulled just fine.

My only complaint is its heavy to lift out of the water. We were camping righ on a lake and kept the boat in the water all week in front of our campsite. It's all sandy and there are no docks so its push/paddle the boat out deep enough and put the motor down which was a real pain if it was wavy and windy. I was wondering if there was a power tilt/trim option for these motors or maybe a reasonable retrofit I could do with one from a bigger motor. It would be really handy to lift the motor up some to get in or out of the shallower water. Any ideas?

 

[tx1961whaler]

Re: 1970 Johnson 40hp coming back to life starting with water pump.

There was not a factory tilt for these. There are CMC aftermarket ones, but they are over 500 bucks.