1971 Johnson 50 overheat quick question

[Jconnell43]

Got my 50 running fine in the tub at idle till the oheat alarm goes off after 2 minutes.
Not sure if it's an impeller or thermostat or pressure relief valve
Is it an impeller check to pull thermostat and cover and see if water exits the hole?
Tstat change is relatively easy compared to impeller change
Should there be a strong stream or a dribble?
If it doesn't I guess I need a new water pump kit.

Thanks,this forum is great!

 

[interalian]

Is the leg deep enough in the bucket? The pump might not be priming if it's too high.

 

[Bosunsmate]

Move the telltale outlet from the engine to the top of the engine then the airbubbles go and you wont get an overheat. Very important

 

[Jconnell43]

Good advice thanks.

I am covering the lower grill completely in the tub.

I might be wrong but I don't think these have telltales per se, I have seen nice telltales drilled into the top, might be in my feature.

 

[flyingscott]

You need the water higher must be above where the lower unit bolts on. That is where the waterpump is

 

[oldboat1]

per your question -- think the t.stat on yours is down at the bottom, and requires a head cover gasket (maybe a head gasket if head removal is necessary to get at the t.stat....). Anyway, it would probably be just as easy to drop the l.u. and service the pump.

If you are not quickly getting spray at the exhaust port, assume it's at least the impeller. If you have a salt water motor, you may have to get in and clean out passages as well -- along with servicing the t.stat.

(edit. assuming the l.u. is sunk deep enough in your test barrel, as suggested.)

 

[jimmbo]

Good advice thanks.

I am covering the lower grill completely in the tub.

I might be wrong but I don't think these have telltales per se, I have seen nice telltales drilled into the top, might be in my feature.

You are correct, no telltale. They didn't appear on Evinrude/Johnson motors until 1978

 

[Jconnell43]

Additional info:
I saw a youtube video of the same engine running and it had water spitting out the 2 vertical exhaust ports at the back.
I have run mine till the siren went off and I never got anything but exhaust, no water as verified with paper towel.
Questions are:
1. In all conditions, thermostat open or not, shouldn't there be water coming out of the 2 vertical exhaust ports after 2 minutes ?
2. If I never have any water coming out, is that definitely an impeller problem or could that possibly be a thermostat?
3. In my old BMW's the default position on a bad thermostat is that it's always open, is it the same on these thermostats?

 

[Fed]

Read post #5.

 

[Bosunsmate]

Drill yourself a new telltale on top of the crankcase just behind the lifting ete , it will solve two of your issues in one easy job