Johnson a65 scored pistons?

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Smokeonthewater
Posts: 45
Joined: Fri Jun 05, 2015 10:36 am

Johnson a65 scored pistons?

Postby Smokeonthewater » Sat Jan 06, 2018 1:13 pm

Good afternoon,
A few years ago, I picked up a Johnson a-65 complete, but very little compression. It would start and run, great, but not in water. I tore it down a year ago, because I really needed a basket case project!
The cylinders *look* okay, but the pistons appear to be lightly scored. The rings look smooth. There was a lot of carbon present in this motor, in fact I wonder if the exhaust is partially blocked. (Any tips on cleaning this?)
While is not my first outboard rescue operation, it is my first tear-down and rebuild attempt. I thought I could use some input from those who have been here before.
Let me try to upload some pictures......
Thanks in advance!
Any leads on rings /pistons and gaskets much appreciated!

Smokeonthewater
Posts: 45
Joined: Fri Jun 05, 2015 10:36 am

Re: Johnson a65 scored pistons?

Postby Smokeonthewater » Sat Jan 06, 2018 1:20 pm

Pictures here?
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Mike Stroz
Posts: 224
Joined: Mon Apr 06, 2015 10:52 am
Location: Massachusetts

Re: Johnson a65 scored pistons?

Postby Mike Stroz » Sat Jan 06, 2018 1:45 pm

I'd try Otto gas engine works in Maryland for rings. I've bought rings there a few times and they always seem to have what I need. Best to call though. They don't seem to answer emails
When in doubt, duct tape!

need2fish
Posts: 49
Joined: Fri Mar 20, 2015 1:22 pm

Re: Johnson a65 scored pistons?

Postby need2fish » Sat Jan 06, 2018 6:12 pm

Before spending your money on rings, mic the bores -- if the runout from the bottom to the top is more than .020 (in my experience), rings may not help -- the balloon in the ring wear zone may be where your compression is going. Given the shape of the piston skirts, I`d say you`ll see some significant wear. Bore should be 1 7/8".

Also, make sure the block is not leaking where it joins the crankcase, and top and bottom crank bearings are not leaking.

Lastly, pull the carb and evaluate the rotary valve for wear or damage.

I have both the A and K inline motors and they suffer when there is carbon build up in the area between the exhaust chamber and the leg. The right angle turns get loaded up with carbon and the motors lose top end and accelerate slowly (because exhaust is not getting scavenged out of the exhaust chamber).

Smokeonthewater
Posts: 45
Joined: Fri Jun 05, 2015 10:36 am

Re: Johnson a65 scored pistons?

Postby Smokeonthewater » Sun Jan 07, 2018 1:13 am

Thanks for the replies! I've got a plan, and some numbers! It looks like a fun motor once it runs..... the ignition on this one is really hot, and the gas tank is in good shape. I've been scratching my head a little on how I might get the carbon out of the leg..... those passages seem so small to begin with...... ll let you guys know what I find out.... it might be a while.... having fun with my 'new' Stevens mag and condenser tester

need2fish
Posts: 49
Joined: Fri Mar 20, 2015 1:22 pm

Re: Johnson a65 scored pistons?

Postby need2fish » Sun Jan 07, 2018 11:54 am

Consider leaving removing the carbon in the leg to last.... clean as much out as you can with a brass brush and / or a dremel. Once it is running you could put some Seafoam through to get rid of the rest.

Smokeonthewater
Posts: 45
Joined: Fri Jun 05, 2015 10:36 am

Re: Johnson a65 scored pistons?

Postby Smokeonthewater » Wed Jan 10, 2018 11:36 am

Seafoam it is! I'll see if I can get a 'snake' through those passages, since I am curious about the amount of stuff that might be in there....
Also, Otto gas works hooked me up with a set of rings at $25 post paid I figure it's a good gamble until I can find out about mic 'ing those cylinders.... if they end up measuring bad, what better place to practice my non- existent honing skills!
Thanks, guys!!


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