1978 Johnson 15 HP. Does not appear to be pumping water.

[The Famous Grouse]

All ideas appreciated folks. I have a "barn find" 1978 Johnson 15 HP short shaft. It was in reasonable condition, but likely has not been run in well over 10 years. It did not run when I got it, but upon a total carb teardown and inspection it was obvious that all seals were shot and it had the old cork float, so I put in a new carb kit including float. She fired on the third pull.

However... She doesn't appear to be pumping water.

I did (I believe) all the usual checks:

1. Checked the indicator nozzle and hose wasn't plugged. Nothing, clean as a whistle.

2. Pulled the thermostat cover. Tested thermostat in cup of hot water. Functions fine. No mud blockage found under cover, extracted one small willow leaf, but do not think this was enough to block it totally.

3. Tore down lower unit and replaced impeller and full water pump. Could not tell if impeller "key" had come out because pump pulled apart when LU separated. Impeller had all vanes intact, so vane not blocking passage.

4. Blew compressed air through all passages and checked lower unit intakes by screen. Everything appears clean, no sign of large scale mud blockage.

Big Question: I'm in MN and it was 38 F when I was testing this thing in a tank outside. In this vintage of Johnson, does the thermostat stay completely closed with no water coming out the indicator UNTIL the engine reaches operating temp?


Or are these like a Mercury where the indicator should always be flowing?

I was afraid of damaging the engine, so I only let it run for no more an a minute at a time. Am I just not letting it warm up enough?

Many thanks

Grouse

 

[racerone]

Re: 1978 Johnson 15 HP. Does not appear to be pumping water.

Thermostat has no affect on the indicator hose !!-------Install a new impeller !!

 

[The Famous Grouse]

Re: 1978 Johnson 15 HP. Does not appear to be pumping water.

Thermostat has no affect on the indicator hose !!-------Install a new impeller !!

New water pump including impeller has been installed. I did it last night and did not have time to test it.

Just wanted to confirm that point about the indicator stream and if the thermostat had to be open for the indicator stream to be present.

Will test again tonight and see if the problem has been solved.

Many thanks for the reply.

Grouse

 

[racerone]

Re: 1978 Johnson 15 HP. Does not appear to be pumping water.

Water must come out the tell-tale imediately.---Thermostat has nothing to do with this !!

 

[The Famous Grouse]

Re: 1978 Johnson 15 HP. Does not appear to be pumping water.

Understood. Will be back with a full report tonight after I test it. Hopefully the clean out and new water pump fixed it.

Grouse

 

[bonzoscott]

Re: 1978 Johnson 15 HP. Does not appear to be pumping water.

As stated, water should start flowing immediately. Its a bit tricky to make sure the key is in correct. Plus, the plate the impeller rides on - you may have installed upside down with water passage in the wrong place. When finished with a pump install (drive off), twist the shaft clockwise and there should be some good resistance from the impeller vanes. If not, the key fell. Also make sure your water tube mated up correctly.
I have a '78 15hp and had to change impeller last season because ear muffs fell down a bit for about five seconds.

 

[The Famous Grouse]

Re: 1978 Johnson 15 HP. Does not appear to be pumping water.

And the Tank Testing verdict was....

Success!!!!!

I'm not sure what, exactly, the problem was. Which is always a little vexing, not having that "ah-ha!" moment where you see the exact cause.

But after replacing the water pump with a full new kit, pulling the thermostat cover, flushing the passages, and blowing everything out, I put it in the test tank last night. And she pumped water like there was no tomorrow after 5 seconds of run time. Water was coming out the indicator, out the above-water exhaust ports, etc.

Ahhh, the sweet smell of spent 2 stroke oil mixed with success!

Good tip Bonzoscott re the impeller and how to tell if the key fell out. Many thanks for that.

Top tips as always. Thanks.

Grouse

 

[racerone]

Re: 1978 Johnson 15 HP. Does not appear to be pumping water.

Proper way to install impeller.---------Put pin on flat surface of driveshaft , held in place with grease.-----------Then install impeller.----Check that pin is in place by rotating shaft and holding impeller.---------Lower pump housing in place while rotating driveshaft in normal direction.----Easy as can be , no chance of missing the pin.