omc guru question

[maloney]

I just had rebuilt my 1998 225 johnson and it has now done about 20hrs. We gave it a compression test and all cylinders were very low on comp 60 to 80 psi. We pulled the heads off and found extreme wear to all cylinder. I mean a lip in the bore at where the top and second rings stop at the top and ablout 3 mm ring end gap. All the rings and pistons were new genuine and the cylinders were nice before reasembly. Does any one have any idea on what can cause such a fast rate of wear.

[BenKeith]

Not an OMC guru but do know a little about building engines and it sounds like you didn't clean the block after having it bored/honed and the honing residue was still stuck in the cross hatches. After honing, a block has to be scurbed well with a bore brush and hot soapy water or steam cleaned to get the residue out. If you can put mineral spirets on a white rag, scrub the cylinder wall and it has any gray on it, you need to wash it again and keep doing this until it comes out white. Only other thing I could contribute that to would be a generally dirty engine when it went together. Don't know of an oil that would be that poor of a grade to cause it.

[maloney]

the dude that built it has built a lot of engines and i was there when he was building it. Yes he did use hot soapy water to clean it before assembly and and then wiped out with white paper to check it was clean.

[Riverratt]

I would not even think the residue would last that long and cause that. Is it possible the vro was on the week side?

[Riverratt]

what brand oil did you use?

[maloney]

yes vro maybe weak but i would have thought it pick up on thrust side of piston and it has not done that. The wear is all the way around the bore ,very clean smooth wear almost like it has done thousands of hours.

[maloney]

have used XD30 oil

[dynobo]

Did you do a check of the ring gap.The ring gap must be such that the rings remain "springy" at all times. If they go solid after heating up they will scuff the cylinder pretty good. As you didn't mention any scuffing I would assume the gaps are not the culprit. Also if memory serves correctly many of the 3.0's had the top ring gap in the boost port so, too tight would have probably caused a ring to catch the lip of the port anyways. Sooooooooo I'm gonna go back 25+ years and switch channels to automobiles and most American auto V-8's used Chrome or some other hardened material for their piston rings, worked great but everytime you had to rebuild with significant miles the rings were practically unscathed and the engine had to be bored .040+ just to clean up. I have seen this hundreds of times. Then sometime around the early 80's (engines) I would start to see worn rings and little wear in the cylinders. I rebuilt a 318 Dodge that had 220.000+ miles on it and it belonged to my dad so I know the oil wasn't changed more than once a year and probably more like every two years. Don't get me wrong everything in the motor that could wear out, was wore out, but the cylinders still had the crosshatches visible. I checked with a dial bore and the cylinders all had less than .003 taper from top to bottom. I have seen many since this one that were wore out but the cylinders still had the crosshatches visible. I doubt seriously this is oil related, If the oil wasn't supplying the proper lube you would have definitely smoked the cylinders on a looper, heck I've seen them smoke with no obvious reason. Only motor design That I know that has a mind of its own. I usually name all my loopers after ex-girlfriends. SORRY!!!! Back to the post; I would check the composition of the rings vs. the cylinders. Or as Keith alluded to, make sure all the carbide material and other abrasives are thouroughly cleaned from the cylinders. Sorry so long, I'm bored; Been watching paint dry all day.....Bobo:D :D :D

[BenKeith]

Now a question for the guru's. Is it posible to put one together with the rings on the piston upside down. That would create a tremendous amount of ring pressure on the cylinders if you could get it to go in the cylinder that way. For the wear he's describing, there would have to be a temendous amount of force on the rings, a lot of abrassive material in the cylinder or as eluded to, the VRO was barely supplying enough oil to keep the bearings from coming apart and not enough to lube the rings. If it was lack of oil, I would think the bearings would be blue when he pulls it down.

[maloney]

It is possible to put rings on piston upside down but then impossible to get piston in bore with rings upside down. The ring end gaps were checked and were all ok . The ring were genuine OMC/bombardier rings.
I am getting a fuel test done to see if there is any thing abrasive in the fuel.

[racer]

How was the engine honed and what grit, what was your finished clearance, factory rings on factory pistons?

[gfinch]

Take pic's and post them. Rings, pistons, walls and bearings. What DO the bearings look like? Please explain XD30 oil for me.

Anyone here remember what was called, the BonAmi treatment?