1984 Johnson 115 Cylinder damage--Pics for opinions.

[rothfm]

Hi,

I got this motor back in the fall as a spare or parts...and I just opened it up to borrow a head for another motor i'm working on. I was surprised at what i found!!! Attached are a bunch of pics for your thoughts on what happened...I have my thoughts on the Prior Owner and what he might have done.

1st... This motor did run, and had 110-115 across all 4, even the cylinder in question. Before I opened the heads just now, the compression again was good.

I am wondering if the Prior owner broke a ring, installed new rings in this Cyl, and closed it up without replacing anything more if there wasnt wall damage?? Maybe they honed the walls? I can tell that the Power-head bolts are new, and I can see new sealant down there too. The head bolts came out easily like someone had "been there" recently.

The damage looks to be on one side of the piston top, and on the matching side of its head. Its nicked up, and "pocked". But the Cyl Walls are very very smooth, which is wierd. If this is an ongoing situation happening "right now", I would expect the walls to be scored badly and find small pieces of the damage. But maybe not....Can rings tear up and damage the top of piston and portion of head and not mark-up the walls? He must of gone in there and did the rings and left everything else

I have no idea really. Thoughts??

Like I said, compression was good..It moves smoothly and absolutely no marks on the walls.

Thanks in advance for opinions.

 

[emdsapmgr]

Re: 1984 Johnson 115 Cylinder damage--Pics for opinions.

The most typical failure on a crossflow engine is when a top ring breaks. The ring breaks into pcs and get blown back into the combusion chamber, where the ring pcs pulverize themselves between the head and the crown of the piston. (that's where all the dents come from.) Usually when this happens, the rebuilder will replace the piston, ringset and the head. With the compression numbers you have it is always possible that it got re-ringed only, re-using all other parts. That's a pretty unusual/uncommon rebuild. I'd do a visual check of that cyl. The piston to wall clearances are fairly loose on this engine. You can move the piston back and forth inside the cyl walls. This extra clearance lets you peer between the piston and cyl wall. Bring the piston up to top dead center. With a flashlight, you should be able to see the top ring. Esp, you should be able to visually confirm that the top ring is wholly intact or not by moving the piston around in the cyl. If it is intact, some type of rebuild was performed, your compression is good, it just looks ugly. That's a best case scenario, and it may run for years that way. However, it is possible you will find that top ring broken. That's a different story.

 

[rothfm]

Re: 1984 Johnson 115 Cylinder damage--Pics for opinions.

emdsapmgr, Thank you. I will try to get in closer to see of that top ring is intact. Yes its ugly and i was surprised to see it really as it was running. The new Sealant and newer powerhead bolts tell me someone was in there. I'm guessing they went in, and put in rings, and sold it like that. I'm hoping thats the case, and that ring is ok.

Do you think if that top ring disintegrated totally, and not replaced, I'd have smooth Cyl walls, and good compression????

Will repost my findings.

thanks for the response, appreciated.

 

[emdsapmgr]

Re: 1984 Johnson 115 Cylinder damage--Pics for opinions.

The engine will run on the remaining lower ring. It may even make good compression-but typically not as good as the other 3 cyls with both rings. When a ring goes, it's not a given that there will also be cylinder wall damage. Depending on the existing cylinder wall taper, you might be able to hone the cylinder wall, put in a new piston and ringset. Usually when you get an engine down this far, it's best to also re-ring/hone the other 3 cyls at the same time. No point in fixing one piston and have another top ring go bad next week.....

 

[Haffiman]

Re: 1984 Johnson 115 Cylinder damage--Pics for opinions.

Has the block itself been split? Look for fresh red Gel Seal II between crank halves.

 

[rothfm]

Re: 1984 Johnson 115 Cylinder damage--Pics for opinions.

Thanks to both of you...going to look closer tonight and see what I can feel with a thin feeler guage...I was hoping to work on this one soon, but maybe it will be a project for next fall...fishing time is soon upon me.

I'll post my findings if it will help others with similar.

Thanks

 

[rothfm]

Re: 1984 Johnson 115 Cylinder damage--Pics for opinions.

YEP, Its ring damage. Not what I expected for good running, and good compression. With a bright light in there I can see most of the upper ring but since its the bottom cyl, the lower portion is hard to see.

I made a then plastic "feeler" guage. Sliding it in at the top, I can easily feel the ring all the way around, EXCEPT 4'oclock to 8'oclock. Thats what nicked up an area of the piston, and head...While the lower is maintaining compression. The walls incredibly are completely smooth (hard to believe).

Looks like I picked the right motor to put on my boat (working on a 1995 88SPL)!! This 115 will be a fall/winter project. That will be fun and give me something to do after the season. Never did anything like that but I'm pretty mechanical and will give it a shot.

Hope this can help someone else that has a similar experience.

 

[toddschubert]

Re: 1984 Johnson 115 Cylinder damage--Pics for opinions.

Go 88spl!!! lol. I love mine. cant hardly beat it for performance under pressure and ease of working on.

 

[emdsapmgr]

Re: 1984 Johnson 115 Cylinder damage--Pics for opinions.

Once the ring cracks, it will start to migrate around the piston ring groove. As it migrates, the broken ring edges will surely catch on the intake/exhaust port holes-eventually cracking the whole ring into small pcs. You've evidently caught it just after the ring first broke. That's good, you may have minimized any potential for cylinder wall damage or port damage.

 

[rothfm]

Re: 1984 Johnson 115 Cylinder damage--Pics for opinions.

Thanks guys, appreciated...While I work and tinker on motors, I havent really gone internal much on them. But I'll save the 115 for a cold winter project. Thanks Todd, Yea the 88spl is newer 1995, and in pretty good shape--I'm glad to that was the one I chose early on to get ready. Replaced a bunch of items on it, and a new paint job. I hope it treats me as well as yours!!