I finally got the engine back in last weekend after getting the crack welded. The engine removal/installation was much easier that I thought, as I think it only took us about 2 hours to get it back in this spring. The boat started back up and we hooked up the engine flush kit to a hose and let it run for about 10 minutes with no water leaking! I tested the boat on the lake today and it ran great, and everything seems to be repaired. It even seems to run smoother, and I think that is due to the spark plug replacement. When I removed the engine I also replaced all of the spark plugs, which the bottom 2 (almost impossible to replace when engine is in boat) were much worse off than the top 4.....I'm guessing they haven't been replaced in quite some time. I had it up to 38 MPH today (slight headwind) at about 5500 RPM
I also had IMPROS re-weld the damage to the stator vanes that seemed to be causing my cavitation when under load. On my testing today, it seemed to have helped, but I only had one other guy on the boat with me. The real test will come when we have 4-6 adults plus kids, but it does seem to be better. I went from idle to full throttle very quickly and heard/felt no cavitation when I would have before, so I am feeling quite optimistic about this.
Since I've had all winter with the motor out of the boat to think about this crack, I'm wondering if this could've been caused by water freezing. I always keep the boat as nose-up as I can while it's on the trailer to help water drain out of the rear drain holes. This could cause water to sit in this part of the engine and not drain out. I leave it in an unheated shed in the Iowa winter, which usually gets down to about -20 at least a couple of times per year. I've probably been thinking about this too long, but with the extent of this crack, I'm wondering if this could've been caused by freezing water....
