1980 Johnson 25hp, is it pumping enough water?

[blankenship_kevin]

I just got this 1980 Johnson 25hp motor with a jon boat purchase. I immediately replaced the impeller. Does it appear to be pumping enough water to keep it cool? Also, does this model have a "pee stream" on the underside of the top housing? Thanks! Here are links to the videos of it running in a barrel.
http://www.youtube.com/watch?v=4lE9htgT6Is
http://www.youtube.com/watch?v=gS5WWfWvuAw

 

[BonairII]

Re: 1980 Johnson 25hp, is it pumping enough water?

Looks to me like it's pumping plenty of water. No idea if a "tell-tale" was factory installed on your motor. Pop the cowling and see if there's a hose routed to the lower shroud. You should be able to see the fitting from the outside of the lower shroud(probably on the starboard side).

 

[blankenship_kevin]

Re: 1980 Johnson 25hp, is it pumping enough water?

Looks to me like it's pumping plenty of water. No idea if a "tell-tale" was factory installed on your motor. Pop the cowling and see if there's a hose routed to the lower shroud. You should be able to see the fitting from the outside of the lower shroud(probably on the starboard side).

Great, thanks! I will check that out. So why would some have it and others not?

 

[BonairII]

Re: 1980 Johnson 25hp, is it pumping enough water?

I believe that telltales became standard at some point, but i have no idea what year. They are installed to make it easier to see if the impeller is working and also prevents air pockets from developing high up in the water jacket. Air pockets will/would prevent water from reaching all areas inside the water jacket. This could cause "hot spots" and possibly an overheat.

There is a sticky here that shows you how to install one yourself. Ironically, I happen to be installing a tell-tale on my '67 outboard later today.

 

[sutor623]

Re: 1980 Johnson 25hp, is it pumping enough water?

I bought an infrared surface thermometer to check the surface heat of the cylinder heads. Thats one sure way to tell if your motor is at the right operating temp. It was less than $20 at radio shack!

 

[BonairII]

Re: 1980 Johnson 25hp, is it pumping enough water?

I bought an infrared surface thermometer to check the surface heat of the cylinder heads. Thats one sure way to tell if your motor is at the right operating temp. It was less than $20 at radio shack!

Sounds like a great tool to use in addition to a tell-tale. Obviously, would be a pain in the butt to use while on the water at WOT.

 

[sutor623]

Re: 1980 Johnson 25hp, is it pumping enough water?

Sounds like a great tool to use in addition to a tell-tale. Obviously, would be a pain in the butt to use while on the water at WOT.

Oh yeah! Definitely more of a diagnostic tool than anything else.

 

[kbait]

Re: 1980 Johnson 25hp, is it pumping enough water?

That one should have a tell-tale (perhaps clogged). The water you see out the exhaust ports has gone past the open thermostat (discharge water drains down the leg there, and exhaust pressure 'pushes' some of it out). When you first start your motor cold (not run in a couple hours) there should be little/no water from those ports until the thermostat opens after a minute or 2. If it's spraying there immediately, you likely have a stuck-open thermostat.

Find the telltale port and stick a wire in the outlet nipple as it's likely clogged there. If not there, then the rubber tube or where that tube connects to the powerhead. Good luck!

 

[blankenship_kevin]

Re: 1980 Johnson 25hp, is it pumping enough water?

That one should have a tell-tale (perhaps clogged). The water you see out the exhaust ports has gone past the open thermostat (discharge water drains down the leg there, and exhaust pressure 'pushes' some of it out). When you first start your motor cold (not run in a couple hours) there should be little/no water from those ports until the thermostat opens after a minute or 2. If it's spraying there immediately, you likely have a stuck-open thermostat.

Find the telltale port and stick a wire in the outlet nipple as it's likely clogged there. If not there, then the rubber tube or where that tube connects to the powerhead. Good luck!

Ok, thanks! I will check it out. If the thermostat is stuck open like you mentioned is it necessary to replace it?

 

[kbait]

Re: 1980 Johnson 25hp, is it pumping enough water?

Absolutely. You want your motor to warm up to running temp (about 150) and stay there. No thermostat = fouling plugs, carbon build-up inside powerhead, decreased performance and fuel economy... decreased engine longevity. You can test yours w/boiling water to see if it opens, then in cool water to see if it's closing. Sometimes they're just gunked-up and cannot close, and you can pick/rinse 'em clean, test and re-install. If you need new, may as well replace the rubber seal on the thermostat itself, and the thermostat cover gasket.

 

[blankenship_kevin]

Re: 1980 Johnson 25hp, is it pumping enough water?

ok, thanks!