Johnson 20 hp

[iowafisher]

I have aquired a 1966 Jonhson 20 horse from father-in-law that hasn't ran in 10yrs. I purchased all new ignition parts and got it running. It runs for awhile then shuts off and is super hot? Is there a water pump on this thing and if so where is it and is it hard to remove?

 

[JB]

Re: Johnson 20 hp

Well there was a water pump when it was new. Sounds like the impeller has disintegrated.

You need a Service Manual, Fisher.

I recommend the OEM Manual. You can find them on eBay now and then or buy reprints from kencook.com. Or you can visit your local library.

Good luck.

 

[iowafisher]

Re: Johnson 20 hp

Thank you i will be buying new parts tommorrow as soon as i tear into it. And thank you for such a fast reply this is the best website i have ever found

 

[samo_ott]

Re: Johnson 20 hp

And dont run it anymore without proper cooling as you'll kill it. There should be water/exhaust coming out about halfway down the back...

In fact you might have already caused damage by running it hot till it stops. You might want to check the compression before spending too much on parts.

 

[iowafisher]

Re: Johnson 20 hp

Thanks guys for the info. I did a compression check today and got great compression now i just got to get a service manual to figure out how to access the water pump to figure out what is bad and what is good.

 

[darrklim2]

Re: Johnson 20 hp

Thanks guys for the info. I did a compression check today and got great compression now i just got to get a service manual to figure out how to access the water pump to figure out what is bad and what is good.

If you are going to replace the water pump impeller you might as well replace everything. The kit is only a few dollars more. For mine it is about $35 for the whole kit and $15 for just the impeller. IMO

 

[BF]

Re: Johnson 20 hp

and don't run it out of water! Muffs don't work on those ones... the primary water pickup is in the screen at the leading edge of the "fin" behind the prop (exhaust comes out the back of it). A garbage can of water is good.

 

[mikesea]

Re: Johnson 20 hp

just a note on the garbage can running,dont run it for long periods unless you change the water,a few posts have mentioned that the small volume of water,mixed with gas, oil contamination can hurt the impeller

 

[iowafisher]

Re: Johnson 20 hp

Thanks guys for your info I have a manual for it now and from what i'm reading i have to disasemble the entire lower unit to get to it?? Am i reading that right? Or is there another easier way to get to it. Also i'm gonna inspect the pick up screen to make sure its completely free of debris since after all it has been in a garage for 10 yrs

 

[F_R]

Re: Johnson 20 hp

Entire lower unit?? Nah, what kind of manual did you get anyhow? Remove the lower unit from the midsection and the water pump is right there looking at you. Your manual should at least show that much.

 

[iowafisher]

Re: Johnson 20 hp

LOL I found that out right after i posted the last response thanks though I'll let you all know what i find even though most all of you already know...

 

[iowafisher]

Re: Johnson 20 hp

got the water pump out and low and behold the impeller came out in pieces i got a new complete water pump kit today. hey thanks guys for all the help

 

[wbeaton]

Re: Johnson 20 hp

Make sure you have all the pieces to that impeller. If even one is unaccounted for it is probably lodged somewhere in your cooling passages. Blow out the cooling passages with compressed air or water and make sure you are getting good flow through them before you reassemble the motor.

 

[floatingwoody2006]

Re: Johnson 20 hp

I have been told to use Carb cleaner to blow out the water passages. I had a yamaha that was completely clogged with saw dust, and this is the only thing that solved it. Good luck./.

 

[wbeaton]

Re: Johnson 20 hp

I've never heard of that. How would you do that?