'71 40hp johnson water pump

[dserwin]

I recently acquired a 71 40 Hp Evinrude and got her cranked and running. My question is how do you know if the water pump is pumping without the motor overheating and doing damage?--is there a tell tale? I want to run it more to test all the functions but I don't want to over heat it unknowingly. How do you know if it is getting too hot?
thanks for any responses

 

[hardwater fisherman]

The cooling water exits from the exhaust relief in back just above the waterline. Look on youtube for the video called evinrude/johnson 40hp ....plenty of water. You should see water right after start up.

 

[racerone]

You should always install a new impeller / pump when you aquire a used motor.---Have seen many failures over the years when folks said " I just bought this motor "

 

[F_R]

Do you have the motor in the water? You cannot test a water pump on any kind of flushing attachment. And a tank must be deep enough to submerge the bulge above the flat cavitation plate. Nevertheless, what racerone said---replace the impeller whether it is working or not. An old one may be working today and shed all it's fins tomorrow.....or spin a hub.

 

[dserwin]

Thanks for the responses! The video on you tube clearly answers my question about what I need to be looking for.
I do have the motor in a tank of water and I ran it only for a few seconds so no fear in overheating. I did not want to run it any longer not knowing if it was getting water flow or not.
A new impeller will be installed as soon as it arrives.
Again, thanks for the information

 

[ssportsmfg]

You can also install a tell tube or pee tube as they are sometimes called. You have to drill and tap a hole at the top of the head, and of course you have to know where a passage is, then install a "L" nipple and a hose and drill a hole in your lower cowling and put the hose through, then when you are running the motor you can look back and see the water coming out of the hose. Water pumps put out way more water than you need to cool the engine, they only cool when the thermostat opens, the excess you can use to get a visual. Put the hole in the cowling on the side where you can view it looking back from the drivers seat. Be sure to keep any metal shavings out of the engine while you are doing the mods. Use a 1/8" barb fitting for the hose of 1/8" id.

 

[racerone]

The 40 hp models from the 60's had thermostats , but does the 1971 model have one ?????

 

[F_R]

No, they didn't

 

[racerone]

And no overheat warning system either.----That is why you install a new impeller every 3 years or so.