20 HP Johnson 1985

TinBoats.net

Help Support TinBoats.net:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

jtm546

Member
Joined
Apr 21, 2015
Messages
6
Reaction score
0
Just bought this from a guy for $450. He hasn't done much to it for 2 years. I looked at the spark plugs and checked the fluid by the water pump. Everything seemed good! It started with first pull. I don't know much about maintaince on it. Is there anything I should do before I put it on the water? Replace water pump? Any help would be great!!

Thanks,

Jon
 

Attachments

  • IMG950116_2.jpg
    IMG950116_2.jpg
    67.3 KB · Views: 901
:WELCOME:

first of all, find a good shop repair manual for that motor.
available on E-Bay or maybe here in the MOTORS forum at the top
where it says "Outboard Service Repair Manuals". (it is FREE to download)

Then, you will be able to inspect, adjust, repair and maintain your motor
so you can enjoy the best performance from it.
 
EZ707 said:
Change the impeller if it doesnt sprey off your hand at about an inch away at idil
Spray off your hand? I've never heard anything like that. Would it be better to hook up a water pressure gauge at the tell tale?
 
Probably. It would be more accurate. An old timer taught me the spray thing. Im not talking a huge spray just enough that it deflects off your finger a little bit. Thats just my way though. Im not a mechanic by any means.
 
I have never done it - never heard of it - of putting a pressure gauge on the tell tale hole.
In my mind, it seems like if you block the coolant water outlet, it may cause problems somewhere.
But that is just me. and, who knows what the acceptable pressure is anyway ??
I have never seen anything or any information that relates to the "coolant outflow pressure".

It only takes a few minutes to drop the foot and inspect the water pump and impeller.
Well worth the trouble to give you peace of mind that that part is in good shape.
An overheated motor is NOT something you want to deal with !!!!!
I think what EZ707 is saying is correct - when your motor is at idle, and there is only a trickle
of water coming out, it is "suspect" of a failing or failed impeller. Drop the foot, check it out.
And, to know the compression of each cylinder will also put your mind at rest.

Now, what I CAN share with you is this ....... I rerouted my telltale water outlet from the
engine block up to the steering wheel so I could constantly monitor it.
(( if you have tiller steer, you could do the same so you can clearly see it while you are driving ))
This is my 1979 Johnson 25hp. As you can see, it is quite a bit more than a sprinkle on your fingers.
And, the motor is at the normal idle speed, in a bucket. Not ear muffs. So there is no external influence
of pressurized water from the garden hose.
25 hp johnson 002.JPG

25 hp johnson 001.JPG

25 hp johnson 007.JPG
 
jtm546 said:
Just bought this from a guy for $450. He hasn't done much to it for 2 years. I looked at the spark plugs and checked the fluid by the water pump. Everything seemed good! It started with first pull. I don't know much about maintaince on it. Is there anything I should do before I put it on the water? Replace water pump? Any help would be great!!

Thanks,

Jon

Nice find. I have the same motor, but a 30 hp.
As previously stated, I would change the water pump and gear oil, its cheap insurance and easy to do.
Here's a video of mine after a water pump change.
edit: Also, if that's a 100:1 label at the fuel connector, remove it and run 50:1.
Good luck.

Barefoot_Johnny, that's a sweet ride!
-jasper

https://www.youtube.com/watch?v=STC7bgueu10
 
Thank you jasper for the advice. I was wondering about the 100:1 that seemed crazy. I will also get a manual before I do anything.

Thanks everyone!
 
Read up on removing the gearcase before you try it the first time. The shift linkage must be done correctly and the first time is a learning curve. If the lower has never been off before, you will have to remove some paint from the shiftshaft to get the fitting to slide off. Watch how the plastic grommets are positioned in the connector. I see them often reassembled in upsidedown position. They are springy and want to shoot off to the other side of the shop when removing or installing. They get lost easy.
 
Bought water pump kit and manual from marineengine.com... Do you guys think I should get a torque wrench?
Screenshot_2015-04-29-07-36-29.png
 
https://youtu.be/o-tiUh8LoFc

This guy in this video above doesn't use torque wrench, and I believe video will help??
 
I think you should get a torque wrench. Whether or not you use it in this application doesn't matter, but everyone should have a torque wrench. :D
 
Smart move on replacing the impeller...even if it pees water if you've got a used motor you should replace it just to know that it isn't dry-rotted or hard & about to crack etc...

For future reference, I've found www.boats.net is usually a bit less expensive than marineengine.com and they're selling the same OEM parts - at least they are for my '84 Mariner. Same idea to the layout of the site with the OEM parts diagram and order sheet below.
 

Latest posts

Top