How much is enough?

[Bugsy]

In 2005 I overheated the port engine--450 hp 6v92--shutting down immediately upon hearing the alarm.
No issues since cleaning the exchanger.
About 500 hours later, I discover water in the oil.
The mech tore down the engine and found both o-rings on the #2 cylinder had failed both in the same area. One o-ring in the
next cylinder was about to go in the same area. The 3rd cylinder rings were fine.
The mech thought the damage was heat-related.
He took the head for testing. A small crack is suspected.
The mech suggests I consider cylinder kits. Wouldn't liners suffice? Wear on the bearings is minimal.
Do I (can I) repair the head? And how much?
And all of this from a momentary overheat 7 years ago?
Does that make any sense?

 

[bobk]

Bugsy,

I'm not knowledgeable in this but can relate a similar experience FWIW.

I found coolant in the oil a few years back many hours after a rebuild. No overheats in my ownership. Because there was glycol in coolant and therefore the oil, the mains were considered 'shot'. The mech said my issue was a mis installed O ring. I did a full rebuild in frame, new bearings, kits etc. Insurance covered their share because they deemed it to be a covered problem. You can search back for more detail. 2010

If your issue was related to overheat, can you be sure it was a head issue vs block?? Just asking. Might change the repair plan.

Bobk

 

[Bugsy]

Thx, BobK.

Actually, what I KNOW is that on the last occasion I ran the boat---and for the 500 or more hours since I had the overheat alarm on the port engine, I had absolutely NO operational issues with the port engine.

I was about to go for fueling and my wife checked the oil levels and reported that there was too much "oil" on the port dipstick. I confirmed that the oil was contaminated by coolant. That "failure" had to have occurred on my last short run.

The mechanic came and began at the top and worked his way down. He reported that the coolant was in the #2 cylinder. He took it out and confirmed that one o-ring was barely holding together. The second o-ring was removed. It was completely broken. The mech pointed out that both were not in bad shape EXCEPT in the immediate area of the break/deterioration.

I then agreed he should look at the other two cylinders on the outboard side of the engine. On one, the o-rings were fine. On the other, one of the rings was deteriorated----again in a small area.

He thought that the damage to the o-rings was consistent with an overheat event.

My only overheat was the ones described in 2005 though last year, the same engine temp went up to 190 (no alarm) and I dropped her down and flushed the exchangers.

I agreed with the mech that since the head was out, it should be serviced. He took it to a shop and they reported to him that there was evidence of overheat and that though they hadn't yet done the required analysis, they suspected a hairline crack. He'll know next Monday.

The mech also said that the shop was of the opinion that if the overheat was sufficient to crack the head, the liners were also probably damaged and that replacement of the cylinders should be considered.

Replacement liners are a LOT cheaper than a whole kit.

My question is whether it makes any sense that a head could be cracked in 2005 and that there would be absolutely no evidence of same until an examination secondary to discovery of failed o-rings.

And does it make sense that those o-rings could have been damaged in 2005 but not fail until now?

I don't want to be "penny wise and pound foolish"---but I would like to understand what happened and assistance in considering the appropriate response.

From an admittedly simplistic perspective, it seems that by simply replacing the o-rings, I will have restored the engine to the condition in which it functioned without issue for 7 years!!

 

[captddis]

don't want to be "penny wise and pound foolish"---but I would like to understand what happened and assistance in considering the appropriate response [

You are in there now. Do it right!
You may well of had an injector failure that took the kit out. I had the same thing happen 253 hours after a through rebuild done by me. I had no symptoms until failure.

As a minimum I would do kits, bearings,recond the good head, replace the cracked head, new injectors, clean aftercooler , regulator and relief valves, airbox valves and anything that looks bad.

 

[rsmith]

But then again at 75 hours per year you could do like some of the others around here and ride around on one engine and save all that money.

 

[saltshaker]

I'll second what captddis said, do it right while you're in there. I can't imagine why you would tear down the engine and only replace a liner or 2, do the kits needed as a bare minimum. It would suck to put it back together and have another failure shortly afterward. I had a failure on a 6V92 that was otherwise in good shape. Damage was confined to one cylinder and I contemplated doing just the one. In the end we did the whole engine, just made sense to do it while it's already torn down.

 

[Bugsy]

That's the consensus---bite the bullet and do it right so even though the head passed the pressure test, I guess we're going ahead and replacing that block and re-conditioning (after testing) the other head---cylinder kits all the way round etc etc.

And the boat is on the market so a purchaser will be getting a deal since the price has to remain the same----and I'll feel better (though poorer) knowing I didn't do only "half the job" .

Thanks for the input.

"Bugsy"

 

[Boatnut]

Somebody is riding around on one engine? Tell me it's not so. You will never convince me it can be done safely in much of a current or wind, but then I guess there are super skippers out there that can do anything.