Now that's it's a new day and have had some sleep; what really happened becomes more clear given
that we now know what parts were involved and have a chronological sequence of events to work with.
It also simplifies things to leave the woody completely out of the equation, since it predated anything in this storyboard.
In the beginning, at your first rebuild while your engine had early, 76cc heads, that first builder screwed the pooch when he used those KB pistons.
Those pistons are intended to be used with the later 120cc heads and produce about 9:1 only in that case. With the early heads that you had at that time, they produced 13:1. This far exceeds any expectation of staying together for long, absent exotic fuel use. Your first rebuild actually fell victim to the exact scenario I described earlier:
Deano said:
. . . A common, and nearly always fatal mistake is to mate early heads with later pistons. This results in nearly 13:1 which will run like a stripped-assed ape for a little bit. Then it grenades an it's done. To much compression requires exotic fuel to not detonate.
A man simply can not swap pistons back and forth between open and closed chambered heads for this reason.
This was why I elaborated earlier, and pointed out how compression is determined:
Deano said:
By design, the compression from the factory is determined by the combination of the heads AND pistons.
The early model (small, closed chamber) 76cc heads produced about 10:1 with the correct pistons.
The later model (large, open chamber) 120cc heads produced about 8.25:1 with the correct pistons.
So . . . what we know now, is that the first rebuild was running on borrowed time right out of the gate, and it was pure coincidence that your friend on the jet ski was a smart ass right when it decided to let go. It would have done the same thing without his involvement.
This also explains your comparative lack of power now. When you clocked 52 on that big ol' boat, that engine was in the "running like a stripped-assed ape" mode, and was in fact self destructing while making that effort. 12 hours is longer than most like that last.
Now after the second rebuild, you have an engine that was at least assembled with the correctly compatible parts and may very well be fine for the long term. The reason I qualify that statement is this; those other seven pistons were exposed to the same abuse as the one pictured. I don't know what lengths your second re-builder went to determine the health of those that survived. Maybe they are fine, maybe they are wounded. It would have been preferable to replace the whole set, but in actuality may not have been necessary. :dontknow:
The one thing that is for certain is that you are not going to regain your lost performance with your current stockish build.
It can and could be done, but without a defined need to go 52 instead of 43, I would call it a day or get a smaller hull to push around.
What to do now? Presumably the engine is still together (ie. you haven't removed the intake yet)?
I personally, dislike taking apart a running engine unless there is a well defined need. As such, if it is still together, I would leave well enough alone and run the 2115 that's on it. The difference is not large enough either way to make me want to buy a new bathtub to put under the stock intake, especially on a 17' hull where the difference will be even less noticeable.
Were I you, I would very diligently perform a cranking compression test and see what I get. My wild ass guess is that you will be around 160ish, although what is more important is consistency. If there is much variance then you should do a leak down test, which could show
that your loss is past the rings, which may be a red flag to your piston's health. If there is only
minimal difference in comp readings (it should only be minimal on a fresh build) I would take that as a good sign and run it. Naturally keeping clean oil/filter will help. I would probably run a bit of Lucas in it as well, just for the extra piece of mind.
One last note: When you do your comp check be sure to record and save your results. Given the unknown condition of the pistons, if it seems down on power later, you'll have a benchmark to compare to. Not that you need to forever hold them suspect, but if you check it whenever you change the oil, you may head off a problem and then not need to worry about it after two or three oil changes.