AHHHHHH piston rings busted! What next??? Help

[cforgan]

I am doing my first outboard engine tear down to reseal the crankcase on my 1974 Johnson 115hp . In doing so I am cleaning all the parts and checking things as I go. I labeled each piston and rods to ensure I place it back in the same cylinder. Well.... I think I screwed up. While cleaning two of the pistons I noticed the rings were wedged into the groove and where almost welded in. So I thought I should clean these to make them loose fit and get the tar out. Well I busted two of the rings. I did measure the cylinder bores and the block has not been bored over sized and is still at the standard 3.5" dia.

My question is can I just buy new rings and install them on the pistons? Then follow the break in procedure to get the rings to wear in. This is my first tear down and the feedback and help is really appreciated!!!

 

[S.A. Baker]

Well...the good part is, a section of broken ring works the best for cleaning the carbon out of the ring lands!

 

[Bosunsmate]

My question is can I just buy new rings and install them on the pistons? Then follow the break in procedure to get the rings to wear in. This is my first tear down and the feedback and help is really appreciated!!!

yes sure, they should still be available.

 

[emdsapmgr]

I'd go further than just replacing one ringset. Do all 4. Your rings are old. Not much reason to just repl one ringset, then have another ringset break in the near future-requiring another compl teardown.... You'll need to hone the cyl walls when you install all 4 pistons. Should run pretty much like new. That carbon around the ringsets is a common problem of these old crossflows. I'd also run some Bombardier Carbon Guard with your gas in the future to minimize the carbon accumulation as your run the engine.

 

[gm280]

I have to concur with endsapmgr with buying and replacing all the rings. BUT, I simply would not just install the new rings and close it up. I would use a hone and break the glaze in the cylinders first so the new rings and walls break in together. But soak the pistons in some good carbon dissolver like the gallon can carb cleaners offer. The ring groove carbon will get really soft and then you can use even a cut popsicle stick to remove the softened carbon out of the ring grooves. Be careful when scraping the ring grooves to not scrape the ring groove walls and change the ring fit... JMHO!

 

[cforgan]

Thanks everyone!!! I purchased a new set of rings for each piston and a drill hone. Rather do this now than having to tear it down again later. Not to mention it sounds like it will be like new again or at least closer to that.

 

[emdsapmgr]

Those 74's had some pretty tight heads. Should make some good compression when you are all done.

 

[Bosunsmate]

goodluck, id also do your upper and lower crankcase seals, they a cheap and a bugger to change if they go when the motors back together. Also if they go the engine runs lean hot and can boom

 

[emdsapmgr]

Agree on the crank seals. Since you will have the whole engine apart, you may just want to buy a powerhead gasket set. Should come with all the gaskets and seals you will need to reassemble. The powerhead gasket set is Bombardier part no: 388602. You will also want to purchase two head gaskets: 318358.