1971 Johnson 50HP compression repair

[Somerowl]

Good day all,
I'm looking for input on this compression situation I'm having.
I've looked through and searched on the issue, but none have addressed potential fixes.
I came across this 50ESL71S for free and built a nice stand (plans and drawings found on this website) to check it out.
After getting it into neutral, squirting some penetrating oil in the cylinders and turning it by hand I have a noticeable difference in compression between the top and bottom cylinders. The top cylinder seems to be inconsistently compressing and sucking while the bottom cylinder has a nice predictable rhythm and pull/push on my finger at the plug hole.
I do have a compression tester and will need to spin it electrically to get a "good" reading, but am looking down the road at this point.
I'm thinking there's either a hole in the piston or a broken/damaged ring on the top piston.
That being said, in order to fix it without removing the bulk of the engine, I'd like to remove the head and fix the appropriate issues from that vantage point to make it as cheap a fix as possible.
Hence this post.
Looking for input.........."don't do that you idiot" or..........." you could do that this way"........or something in between?
I'm not a novice at rebuilding motors and am willing to learn.
Thanks for your help!!

 

[racerone]

How did you get it into nuetral ?---------When that motor is not running it is in forward gear, has to be if everything is in order.------It does not shift untill the motor is turning !----Powerhead has to be removed in order to do repairs to pistons / rings.----But remove the head to see what is wrong would be step # 1 gere.

 

[flyingscott]

Do a proper compression test first just jump the starter from a battery. Thumbs and fingers lie

 

[Somerowl]

Will do the compression test. Perhaps the shaft is broken as well, I just moved the circular lever on the side of the unit, but, if it defaults into forward gear, either I didn't notice the shaft spinning (no prop) or the drive shaft is not connected or broken.
Will let you know the results of the proper compression test.
Thanks for your help!

 

[Somerowl]

Shaft is turning, good news! Now to "Borrow" a battery...............

 

[Somerowl]

Ok, here we go..............
The loaner battery spun the starter, but it didn't jump up to engage the flywheel. That meant off to this forum one more time to decipher the issue. Everything pointed to not enough juice and/or a sticky bendix. Removed the starter, cleaned and lubed the gear (white lithium grease) and it would spin still, but only engage the flywheel if I "walked" it up to engage manually and spun the motor. The loaner battery might not be spinning it hard enough, we'll deal with that in the future if there is one for this beastie.
Pulled out my compression tester and it would not register anything. The tester itself had seen better days, so, in the spirit of "got nothing to lose" I took it apart, cleaned it up and got it to work.
So, I enlisted the boy (15yr old Freshman) to hold the compression tester and we spun it.
Guess what, Compression!
OK, we only registered 75psi on the top cylinder and 100 on the bottom, but there was compression and it could easily be due to sitting for so long.
A fringe benefit of the exercise was I was able to view spark between the plug wires and the block, sweet.
So, now what guys?
Do I try to give it more oil in the cylinder with a squirt can and see if that changes anything?
Do I just try to get it started?
I was not able to get it to spin with the selectric unit, but went direct power to the starter.
Should I go through the control first?
Super excited (can ya tell?) and am very optimistic that my 50 will be hanging on the back of my StarCraft Mariner soon!
Thanks for all your help to date.
Nick

 

[F_R]

That is way too low compression (assuming your tester is working). Don't mess with anything till you resolve that question. Just FYI, broken pistons/rings were too common on that model.

 

[Somerowl]

Can I replace the rings by removing the head alone or do I need to remove the whole Powerhead to do the work?

 

[racerone]

It has already been stated that the powerhead needs to be removed to do internal work !!

 

[Somerowl]

OK, understood, when you said broken pistons/rings are common on this model, is there a way to upgrade their robust characteristics with a certain rebuild kit manufacturer etc? I don't mind going through the whole motor if it's going to give me a good unit for the next 10 years.
Any input is welcome, thank you.
:hail:

 

[flyingscott]

Yes wiseco pistons usually are a better improvement over the originals.

 

[Somerowl]

Got it.

 

[Somerowl]

Ok y'all, got the flywheel, carbs, linkage, starter and almost all of the wiring system removed except for the three wires (one pair at one location and a single at another location) that seem to be entering the powerhead itself. Can someone help me with their removal and also let me know if I need(or should) take the lower unit off as part of the powerhead removal?
Thanks!

 

[Somerowl]

Good day,
I got the cover off with the choke wires leaving all the wiring removed from the motor. The inside from what I can see doesn't show me any catastrophic problems at least. I've got all the bolts out and have about a 1/8" separation evenly all around the base of the Powerhead. I'm afraid to pound on it, but I do have it suspended slightly still in my engine stand but with all the weight being pulled up at the engine hoist point.
Everything I've read says do NOT pry between the two surfaces to keep from damaging their mating characteristics, so where to apply a little more force then?
Any and all suggestions greatly appreciated. Really looking forward to getting her running again...........
thanks,
Nick
:hail:

 

[racerone]

How many bolts are taken out----And did you remove the one nut at the back ?

 

[Somerowl]

Sounds like I missed the "nut at the back", where might that be? I've got it probably 1/4" separated all the way around right now.
thanks VERY much for your help racerone.

 

[racerone]

Below the cylinder head.----Not hard to find.-------Unless the previous mechanic left this nut off.

 

[Somerowl]

OK, behind the inspection plate at the aft of the exhaust housing? I'll check that tonight. I did have separation of over 1/4" all the way around evenly, but I could not initially get those two screws out holding the plate on. Will do tonight.
Thanks,

 

[racerone]

???---------------No , it is under the cylinder head and in the middle.---You should be able to see it in plain view !!

 

[Somerowl]

OK, I'm pretty sure I didn't see it, just the 8 (four on each side) of the main nuts on studs and the four mounting bolts on the inside. I'll look again tonight and send a picture if I still can't see it. Thanks for your patience...........