Stuck piston ring

ChesapeakeChiller

I have researched this online but I trust some members on this site and was hoping to get some feedback from them.

2004 6.2L Mercruiser Horizon FWC inboard 307Hr

I bought boat late last fall, port engine risers/manifolds had just been done but not starboard engine. The survey and compression check were good, boat achieved rpm at WOT. I ran the boat for 2 weeks (a couple hrs) no problems winterized and stored. This spring before launch I had marina do risers/manifolds on starboard engine, they found almost no compression on 2 cylinders due to valves (could see some corrosion) sent heads out had them redone.

Now those 2 cylinders have improved to low compression 100psi. Sounds like stuck piston rings and the boat has not been run yet to see if it frees up so this may be a bit premature. They are replacing water pump today then run and see if compression improves. If it does not is there anything I can have them do to help free up the 2 piston rings before pulling the engine for major work?

jhofmann

Penetrating oil is used to free up a piston that won't move due to the rings being rusted to the cylinder wall (called summer seize in the snowmobiling world). I like 212rowboat's idea of honing the cylinder with the piston at it's lowest point to use friction to try and move the rings. If all else fails, you could try using oil as a last attempt before pulling the motor.

Dream_Inn

CC, I'm assuming that Brian is working on this?  I'll be real curious what they come up with, as I believe you have the right people working on this.

ChesapeakeChiller

Yes Brian is working on this and he may have suggestions before major work. I think I am just a bit nervous about this and trying to get to far ahead of it.

Handymans342

There is something you can spray in the cylinder. Penatrating oil I think

ChesapeakeChiller

Handy, yes that's what I have been finding online. A lot of different products to put in oil or on cylinder to help with this but I don't know or trust those people and fear some of those products could cause other issues. Hoping to get some feed back on here of what product and procedure to use if any.

212rowboat

if you didn't have the heads back on, you could buff the cylinder walls... believe it or not, you don't want lubricity, you want some drag to free the ring.  the cross hatching of cylinder walls is done for that reason- to promote rotation of the rings before they settle... it's a bit of a calibrated crap shoot that they don't align.  

did you see the bores before the heads were planted? what kind of condition were the walls in?  

but even said- run the engine to temperature.... after a few cycles of this it is likely to break free anyway... 

ChesapeakeChiller

I did not see the bores but the mechanic is good and I assume he would have checked. I will talk with them today to make sure. I have my fingers crossed that it will just free up when ran. I am just trying to have a back up plan in mind if I get bad news so I can keep them moving on this. I don't want them to put me up and move to the next boat just yet.

Handymans342

Ask the Grease. He has a lot of experience with sticky stuff. LOL

ChesapeakeChiller

LOL as much as I like talking to the greaseman I don't think I would take much advice from him.

BellevilleMXZ

Seafoam or GM carbon cleaner works well....let it sit for a day or 2 then change oil
......penetrating fluid doesnt work well.....and don't hone it.....very big risk of oil consumption doing that.  That said if cyls look clean will.probably ly free up itself. ......can always use seafoam after. ......just pull plugs on bad clys and pour in through plug hole on preferably hot engine

youstolemybeer

been there done that,  if the head is still off spray seafoam over the piston and let it soak for an hour. Then wiggle the piston back and forth in the cylinder. wiggle it and dump more seafoam on the piston. Let it soak, then wiggle again. This loosens all the rust/carbon/crud built up in the ring lands. after a few times of this the rings should loosen up. If the head is back on, then just pour the seafoam into the sparkplug hole and let it soak for an hour, then start it up 

BUTT with this engine being a fuely injected engine I would doubt you have a carbon build up.

212rowboat

sometimes rings just align, or, they stick... 

I asked a builder about this, and he spoke the obvious after squinting at me for a good solid second... he asked "Heads off?" and went on to answer before receiving response- he said to drop the piston to BDC, and 'tap' it around the perimeter with the handle of a mallet and another mallet... BDC because the skirt has a mill or two less tolerance on a marine engine in the unusable bottom of the cylinder (which answered and age old question of mine, "what are the differences in a Marine block compared to a Auto block?).. the wrist will wiggle and free up more often than not stuck rings.. .

"heads on" was the next question and same thing (response not needed) saying "compressed air in cylinder on compression stroke starting at BDC and bumping starter all the way to BDC of power stroke, then fast turning it a few cycles stopping at BDC/compression stroke again- adding a touch of oil, like you're doing a leak down test at TDC"...

but he also said "run the *&%*& thing".... nothing will assist like heat and varying RPM's..  

ChesapeakeChiller

Just an update, went with marina on test run and something let go in the bottom end of the engine. Back onland waiting for new motor or rebuild.

Handymans342

Good luck