Catastrophic failure on 175 Oceanrunner

[Hankamatic]

Greetings All,
I'm looking for some opinions as to why my 1995 175hp Johnson Oceanrunner ate a piston ring last weekend.The engine has just over 300hrs.The plugs all look to have a nice brownish hue so i'm ruling out lean condition .The motor ran flawlessly all day and on the run back to shore ,within sight of the landing (thankfully),boom she let go after a 17 mile run at near wot. I use Penzoil synthetic blend and have in most all of my previous outboards without a problem.
Generally the 175 would run wot near 6k @46mph fully laden. Since adding a T-top last month rpms seemed to have fallen to 5.2k @ 41 mph. On the day she blew we had a fair amount of weight on board but everything seemed ok. I chalked up the RPM loss to the t-top. The following day I removed the cyl head and found pieces of ring imbedded in the top of the piston . The bore looks good and I'm hoping to just replace the piston, pin bearing and rod bearing and get back on the water,but I need to find the cause as not to repeat the event.
If any of you fine folks have had a similar occurrence or care to offer an opinion as to why this may have happened It would be most appreciated. Thanks in advance for your Time.

Hank

 

[angus63]

Re: Catastrophic failure on 175 Oceanrunner

Welcome!!!!!
Very sorry to hear your story. I run a E175exeo myself. After 500+ hrs, still have 105-110 psi all cyls without issue. Do you decarb regularly? Its not unheard of for a ring to break up after 300 hrs. Using QL77jc4 or QL78yc gapped at 0.030"? Using 87 octane? WOT timing correct? Carb for bad cyl clear? I'll be paying close attention.
Good luck

 

[Silvertip]

Re: Catastrophic failure on 175 Oceanrunner

When you get it apart, check the ports on that cylinder very carefully. Chances are the ring caught the edge of the port and broke. There are a few reasons but a stuck ring due to carbon build-up is just one of them. A lean mixture on that cylinder can damage a ring land causing the problem as well.

 

[angus63]

Re: Catastrophic failure on 175 Oceanrunner

Hank
Any more news or answers to ? above????


...Bump...

 

[Hankamatic]

Re: Catastrophic failure on 175 Oceanrunner

Thanks for the replies,

Sorry to only be getting back now, been terribly busy.

I'm running Champion QL78YC plugs, 87 octane (% of ethanol unknown).I'll assume the wot timing was on or nearly on as the boat was running pretty close to normal (though I won't completely rule timing out). I have a picture of the piston and cylinder head I will try and post.

At this point I suspect carbon. It was actually time for maintenance ,but the grouper bite was so hot i couldn't resist putting it off for a few more trips, (Definably my bad!) after all it's Johnson not something designed by Porsche. No offense to any Verado owners it just seems like they need a bit more care and feeding than the old workhorse looper.


Ok, so the picture things not working out.I'll post them after I figure this little puzzle out. Thanks again for your time and interest.

 

[DJ]

Re: Catastrophic failure on 175 Oceanrunner

5200 is lugging/working that engine pretty hard. That and carbon build up probably got it.