1966 Johnson 3hp advice please

[ray 6688]

Hello all.
I have bought a seized 66 johnson 3hp model JH21E C504192.
I just love the design of these motors.
The leg has been removed and drive shaft is free to turn prop.
So I have removed the exhaust cover/plugs and can see pistons,all looks ok in
cylinder bores,but the crank is solid,only turns a few thousands of an inch each way.
As it is a tiny engine I don't want to force anything.
Have you any ideas how to free motor?
I have no chance of picking up a manual for this here in England.
One other question,when I look at the drive end of the crankshaft I cant
see an oil seal just what looks like a split bush?
would appreciate any advice.
Thanks
Ray

 

[lindy46]

Re: 1966 Johnson 3hp advice please

You can try pouring some penetrating oil or Seafoam into the cylinders and let it soak at least overnight. Sit the motor with the plug holes pointing up. After it's soaked for awhile, take the pull start off and try turning the flywheel by putting a wrench to the nut on top. Turn it clockwise when looking down on the motor. Hopefully it's just stuck rings and that will free them up.

The top of the driveshaft should have an indent where an o-ring/seal goes.

Good luck!

 

[F_R]

Re: 1966 Johnson 3hp advice please

"One other question,when I look at the drive end of the crankshaft I cant
see an oil seal just what looks like a split bush?"

That is correct, there is no seal. You are looking at the bushing halves that are cast into the case.

I guess you know you have the "heavy duty" model, right? That is, it has a right angle drive with large prop for pushing sailboats. Evinrude called their models Yachtwins.

 

[jp498770]

Re: 1966 Johnson 3hp advice please

I had a 7 horse with the same problem. Try spraying some PB Blaster penetrating oil spray into the spark plug holes. Turn it on it side and let it sit for a few hours or even days. Put a wrench on the crank and try to break it loose. Hope it works!

 

[ray 6688]

Re: 1966 Johnson 3hp advice please

OK Thank you everyone.
Will do as you say, and leave motor to soak for a couple of days.
Anyone know if parts are still around for these little engines,
iboats don't list back earlier than 68 which as I expect you all know was a totally different motor.
Thank you all for your advice,much appreciated
Regards
Ray.
PS
No I had no idea it was a heavy duty engine !

 

[F_R]

Re: 1966 Johnson 3hp advice please

OK Thank you everyone.
Will do as you say, and leave motor to soak for a couple of days.
Anyone know if parts are still around for these little engines,
iboats don't list back earlier than 68 which as I expect you all know was a totally different motor.
Thank you all for your advice,much appreciated
Regards
Ray.
PS
No I had no idea it was a heavy duty engine !

Sure there are lots of parts. That motor was made for many years. What do you need? Some parts are same as '68, some are not.

 

[ray 6688]

Re: 1966 Johnson 3hp advice please

Hello all.
Just to say all your advice was bang on,it was 2am here when I sent the
question and as all the shops had closed (except wal mart-they never close)
Any way I had a look around the garage and found some model glow plug
fuel some power steering fluid and some paint thinners.
So I mixed up all three and poured it into the plug holes as you told me.
tried a socket wrench on flywheel nut this afternoon and yes pistons had freed and motor
turns over nice and smooth.
F R if you have a parts book and happen to read this message would you be kind enough to let me know the part numbers for-
Piston rings
Head gasket
Water pump impeller.
My sister is going home to Florida for Easter,but I will be staying in the UK
if I could give her the part # she could bring them when she returns to England.
Many thanks
Ray

 

[F_R]

Re: 1966 Johnson 3hp advice please

Hello all.
Just to say all your advice was bang on,it was 2am here when I sent the
question and as all the shops had closed (except wal mart-they never close)
Any way I had a look around the garage and found some model glow plug
fuel some power steering fluid and some paint thinners.
So I mixed up all three and poured it into the plug holes as you told me.
tried a socket wrench on flywheel nut this afternoon and yes pistons had freed and motor
turns over nice and smooth.
F R if you have a parts book and happen to read this message would you be kind enough to let me know the part numbers for-
Piston rings
Head gasket
Water pump impeller.
My sister is going home to Florida for Easter,but I will be staying in the UK
if I could give her the part # she could bring them when she returns to England.
Many thanks
Ray

Piston rings are 378412 (set of two for one piston)
Head gasket is 203130
impeller was 277181, superceded by 434424
You will need new connecting rod lockplates (4) 307578

 

[ray 6688]

Re: 1966 Johnson 3hp advice please

OK great
Thank you very much for your help F R.
Much appreciated.
Best regards
Ray.
Will buy you a pint next time I see you in pub !

 

[1946Zephyr]

Re: 1966 Johnson 3hp advice please

I would do a compression test, before you go through the expense of tearing it down and rebuilding it. I brought home a motor last month that was stuck and once I got it spinning nice and free, I got 100psi in each hole. It may even be better now, since I ran it for an hour (after the compression test.) I have a 3hp also and compression on that is 60psi per hole. I think if you get this (or better) then you should be good to go. Sometimes these little motors get stuck, from sitting for a long period of time.

 

[ray 6688]

Re: 1966 Johnson 3hp advice please

Thank you 1946 Zephyr.
My next question was going to be what is the normal compression for these
little motors.
Did a test this morning and got around 65 psi on both cylinders,so I guess I'm
good to go.
Regards.
Ray

 

[tx1961whaler]

Re: 1966 Johnson 3hp advice please

Thank you 1946 Zephyr.
My next question was going to be what is the normal compression for these
little motors.
Did a test this morning and got around 65 psi on both cylinders,so I guess I'm
good to go.
Regards.
Ray

I'd run double oil for a while. If it is a 1966, then the normal ratio should be 50:1, so if you run it at 24:1 for the first gallon or so it certainly won't hurt it.

 

[1946Zephyr]

Re: 1966 Johnson 3hp advice please

That engine should still be run with 24:1 reguardless. There are no needle bearings in that motor.

 

[ray 6688]

Re: 1966 Johnson 3hp advice please

Hello 1946 Zephyr/tx1961 whaler.
I was very surprised to find no needle bearings,in fact it reminded me of the British seagull engines.
The fact that seagulls need a 10/1 mix due to bronze bearings should have
made me think about the use of a 25or30/1 mix.
I just used 50/1 in all my omc engines.
I Will use your recommended fuel mix.
Thank you both for your help.
Enjoying working on this little motor, it is very well built ,nice strong internals plus 60s looks.
Seems a shame to use it !
Best regards and thank you.
Ray