1967 johnson 20hp help

[fireman12]

so i have this motor, prob. has not run in 30 yrs, did complete overhaul of fuelpump, carb, lower unit, etc. and somehow got it to run. The only question is, how do i know if the water pump is working, i cant seem to find a water pump indicatior and it seemed as though it was running hot.... I really dont know much about this motor, with its age on it. does it even have a water pump indicator on it. i have the special waterhose hook-up for the water intake on the motor, i just dont know how to tell if it is pumping water and cooling properly. Any help would be greatly appreciated....

 

[lindy46]

Re: 1967 johnson 20hp help

You should get a fairly good spray of water out the exhaust relief port on the back of the leg of the motor. HOWEVER, if that water pump impeller is 30 years old, it MUST be replaced. I wouldn't trust it even if the motor pumps water when you test it. It could fall apart at any time.

 

[tashasdaddy]

Re: 1967 johnson 20hp help

welcome to iboats. click on picture to enlarge.

agree. also change the thermostat.

bright green is exhaust relief port, you should get atleast mist and droplets at idle, more if you rev it up a little.

red is water intake pick up.

yellow is the exhaust.

 

[Harry B.]

Re: 1967 johnson 20hp help

The "earmuff" hose hook up doesn't work on that motor as the water pickup isn't in that screen area, its lower on the fin that drops below the cavitation plate (the red area indicated in Tashasdaddy's illustration).

You've been running it without water if you've used the water hose muffs which is hard on the motor and the impeller.
I'd replace the impeller either way, put it in a 55 gal barrel and give it another whirl. The impeller should fill your hand full of water very quickly if it's working, idle or fast idle. (never rev motor in barrel in gear).

 

[samo_ott]

Re: 1967 johnson 20hp help

When it is running properly you should be able to touch the head (where the spark plugs are) for a few seconds and not burn yourself. Also if you splash water on the head it should not sizzle off immediately, if so, it is too hot.

 

[craigjudge]

Re: 1967 johnson 20hp help

I know it's an old post but I'll add to it in case anyone else uses it for reference. You must submerge this motor in order to get water through the pump and into the head. I just went through this procedure. If the pumps working you'll see water coming from the exhaust located just above where the lower unit separates. Best way to test it is to remove the thermostat first then start it up and see if it's spitting water. If it is, the pump is ok but the thermostat could be bad. If not, change the out the pump. Just a side note; I recently had a no water circulation problem. Upon inspection, I found the pump looked to be fine. I noticed the rubber seal that fits over the pick-up tube was completely broken apart and had clogged the tube. I removed the lower unit and thermostat and ran water through the inlet and outlet tubes to ensure there were no obstructions. I installed a new pump, seal, and backing plate. Shoots out water like old faithful. I am the fourth generation owner of a 67 20hp motor and hope there are four more. It's a great motor. Mine is on a 64 Grumman 15' aluminum. Runs great (once it's.....wait for it........on plane).

 

[dlynn]

Re: 1967 johnson 20hp help

I've inherited a '68 20hp Johnson from my son who traded it for some video equipment.

I had a 9hp Johnson that I had great luck working on due to finding a free download of some "how-to" info on that motor.

I want to change the impeller on the 20hp. Does anyone know of any "how-to" free downloads on the '67 - 20hp?

Thanks in advance.

 

[asdasc]

Re: 1967 johnson 20hp help

I think it is VERY similar to my '59 18HP. It is very simple. There is an oval plate on the side of the leg with 2 flat screws. Take that cover off and fully remove the lower bolt which allows the shift shaft to seperate.

(Note: never remove a phillips screw on a Johnson motor!)

There are 4 or 6 small bolts and one big bolt holding on the lower unit. Remove them and the lower unit should drop right off. Looking at the top of the lower unit now in your hands, remove the small screws holding the pump assembly in place. Keep track of the 'key' in the shaft for the impeller. 99% of the time the housing is fine if you have a fresh water motor. Simply replace the impeller making sure the fingers are shaped in the pump the same direcation as the old one. Re-assemble it and you are all set.

If you need more specific info, just post a picture of what you are stuck on, and we will walk you thru it.

It is easy once you get up the courage to start pulling bolts.

Have no fear!

 

[samo_ott]

Re: 1967 johnson 20hp help

The 18's and 20's are all the same...

 

[dlynne]

Re: 1967 johnson 20hp help

Guys....thanks.....!!