Late 60's Johnson cooling system question

[jm113]

I recently purchased a late 60's 40HP Johnson outboard. I was told at the time the water pump impeller needs to be relaced. The exhaust port for the cooling water has a steamy mist instead of a stream of water coming out. I found the impeller locally for $21.00 but cant find anyone around locally (Sanford FL) to install it. Is this a job an amature can tackle? I do have basic car repair experiance.<br /><br />Also I was told this motor is from the 60's I have no confirmation on that. I cant find a model number on it anywhere. I have attached a picture of it. <br /><br />Any guesses as to the year?<br /><br />

 

[Fouled Plug]

Re: Late 60's Johnson cooling system question

Replacing an impeller generally is an easy do-it-yourself job, and cheap too. Get a manual for that old unit and you'll be set. Wish I knew the year for sure, but with the model and serial numbers an OMC place will be able to get what you need.

 

[Dunk]

Re: Late 60's Johnson cooling system question

She looks like a 63. If you look and the starbord side of the engine leg you'll see a plate with two screws. Remove it. Inside there is another plate, remove it. You'll see a bronze coupler with two 7/16" bolts going thru it. Remove the bottom bolt in the coupler and loosen the top one. Now you have the shift shaft disconnected. After that remove the bolts holding the lower unit on. It might be easier to see what you are doing if you remove the cover on that 5" extention. Don't forget the big bolt in rear. The gearcase should drop out of the engine at this point.<br /><br /> The water pump housing will be at the base of the drive shaft on top of the gearcase. Remove the three screw and lift the housing off holding the drive shaft down. The only thing holding the DS in is the key in the water pump impeller. I wouldn't pull the DS out of the gearcase, if the pinion gear moves out of place you'll have to take the geacase apart to aline it. If the DS shaft is rusted you may need to sand it to get the impellers off and on.<br /><br /> If you mail me I can scan the part manual page and shoot it to you by email. It gives you a blowup of the whole gearcase and you'll be able to see what seals and orings you need if the one on the WP are bad.<br />Dunk@plexi.com

 

[jm]

Re: Late 60's Johnson cooling system question

Ok I have disconnected the conecting rod, removed all 6 bolts from the bottom, and the long bolt in the back. What have I missed????? The lower unit will still not come off. HELP!<br /><br />John<br /><br />

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[jm]

Re: Late 60's Johnson cooling system question

Wahooo!!!! We got it done. After hours of work we got the water pump replaced @ 3am! Thank you Dunk for all your help. You ROCK!<br /><br />Now for the bad news. I don't see much of an improvement in the exhaust water. The water still comes out in a spray rather than a steady stream. Is this normal? The amount of water and pressure has increased but I was told I should see a stream of water with the new pump.

 

[Lark40]

Re: Late 60's Johnson cooling system question

These old Big Twins aren't designed to produce a nice stream of tell-tale water as some other brands do. If your engine is producing some spray at idle, and considerable spray when throttled up, then that is normal. Of course, it may take a minute or two for the thermostat to open up before you see any output.