Not good....

[froggy]

Kevin,

Somewhere, in the dark recesses of my memory, I seem to remember that the, plastic(nylon), oil pump drive gear is two piece(glued together) on all the merc's except the opti's. If this is true, your oil drive gear may have separated and will work fine hand turning but not when running.

froggy

 

[John Richied]

If you going to mix @ 40:1 even with 100% synthetic oil you have increased your chances of carbon build up. I’m not saying it’s wrong to do in my opinion, after all oil is the film of protection. I’m just suggesting you decarb twice a year if you run much or use Merc Powertune once a year and run the Yamaha Ringfree (or your favorite equivalent brand) at a maintenance dose now and then.

I’m a fan of preventing the carbon from building up, not letting it build up then shocking the engine and all the carbon (a substance as hard as diamonds) lets loose in your engine.

When you take the heads off and decarb you get a lot more then just spraying it through the sparkplug holes. I use a 3M pad on the top of the pistons and gasket surface that’s called Synthetic Steel Wool, its not steel wool so you are not putting little pieces of steel in your engine.

When you get your engine back you might also want to check the mesh fuel filter screen that’s just after the electric fuel pump, cleaning it is easy and it shouldn’t need replaced (item 10 in the picture on my ProMax). Then the micro screens they put in the fuel injectors themselves, I removed these because if something makes it that far I hope it passes through the injector being it would be very small. If it doesn’t pass it would plug that screen and cause a lean condition (no fuel = no oil) on that injector/cylinder.

The information I have passed on here is just what I do and have learned from others and my personal experience, if you have a like or better way that’s cool.

 

[Kevin from FL]

Every fuel, oil, and water related component has been looked at, flowed, and disassembled. All checked good except for the oil drive sensor.

We found another lower cylinder that was starting to get the 360 degree scuffing but nothing has been found to have caused it.

I can assure you John, a decarb maintenance program has already been planned out

 

[Yellowallison]

KEV!!!!!!!!!!!! :?:

What the HECK!!!!!!!! :?: Yur slackin.... :x I see brown speck of grass over there near the T's planter ......... :roll:

Time for you to resod aint it! HAHHAAHa! :mrgreen: :mrgreen:

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Yu guys otta see Kev GRASS.... that chit thicker and prettier than The best daggum BURBER carpet!

 

[flatout]

Ive seen quite a few blown pistons in my day! Those look a lot like the pistons got too big for the bore. Overheated pistons grow faster than the bore size causing the clearance to become "0" or less. The result is aluminum plated cylinder liners! The good news is it looks like there are no scratches so a good honing and a couple of new pistons and "there you go!!!." The cause looks like a bad water pump or a blown water pump gasket. I have replaced a couple of pistons right on the boat without removing the powerhead. Honed them out without a problem. Just be sure to stuff a good rag down on top of the crank to prevent any honing oil from getting in the bearings. make sure to flush and reflush the bore. I always use spray 9 as my final cleaner to remove any embedded hone grit.
Howard``````>=/">

 

[Kevin from FL]

Could have been that Howard but we found nothing that would point a finger to the cause. It's strange to say the least. I hate a mystery like this with no root cause's found. I've been involved in many crash investigations over the last 30 years on jet engines and some of them we found no cause for the failure.

We re-sleeved the two real bad cylinders and everything cleaned back up to the standard bore size. Insurance covered it so I lucked out on that

Thanks for the input.