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Damaged piston in Honda BF 225

hondatic

Member
Have been working on finding the knock in an older 225, low hours reportedly when I bought a pair on a catamaran. One engine developed a knock shortly after I got the boat back to Alaska and ran it for two hours. Upon initial inspection before I bought the boat I watched the mechanic compression test the engines and all cylinders on both engines were 200+ psi. After a few test runs I left the boat with the dealer selling it used in FL and went fishing, returning a week later to have a final inspection and sea trial. Some minor mechanical issues were discovered by the mechanic and were supposedly addressed before my return. Engines ran good on final sea trial.

After discovering the knock, compression on the middle cylinder on right bank was just over 160 psi, all others still over 200. Engine starts and runs fine though I haven't done more than idle since knock appeared.

After sitting on the stand in my shop for a year I finally got to the motor and started tearing it down. Took off the starboard bank cylinder head where the knock seemed to be originating this morning and wow. Middle piston is trashed. It looks like a valve dropped in and went around for quite a few rotations before either it shut the engine off or someone shut it down. Cylinder is clean, no debris at all came out when the cylinder head was removed.

The dealer never mentioned anything happening, piston lining is scored.

The troubling thing is that all four valves are intact and in perfect shape. The cylinder head on that hole looks fine.

I expect they replaced the cylinder head between sea trials and never said anything. I imagine it bent the connecting rod and took a while for the bent rod to wear through the bearing enough for it to start knocking.

Wanted some advice from some with experience on what is best course of action? Can the cylinder liner be replaced along with a piston and rod? Is it likely that the crank is fine after such an incident? Is a short block the best bet in these instances? The cylinders on the other two pistons look brand new. Not even a hind of any wear on the sleeves. I suspect the engines really do have low hours but have sat for 10 years which is probably worse than running hard.

Any suggestions or past experiences would be welcome. All valves look to be seating fully and properly, I expect this is a different head than the one that was on the engine when the piston was damaged. I have attached a photo of both.
 

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Wow - that's a bummer! While it's not likely your problem, my dad had a car worked on that showed similar problems. His was caused by a dealer that didn't peen down the screws in the carburetor. One loosened and backed out - finding it's way into the engine. But, we did recover the screw upon removal of the head. I wonder if you have something similar - and it found it way out the exhaust valve and that's why you didn't find anything in the cylinder? That's a long shot, so likely your theory is more probable. If so, you have some discussions to have with them. Good luck as you work through this.
 
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