Well, last night at the lake wasn't so bad. My son's flex-shaft held together, no problems there.
Cranked up my ship, put her in the water and about 50' from shore, the engine quit...just as I was starting to get her going. Brought it back, adjusted the low-speed needle and the high-speed needle a little (maybe because I was using the new NGK plug?). Back in the water, she ran just fine. Good low and high speed running. No misses, no problems. Went back to 16:1 oil mix...just to be sure.
We had three good runs of 8-10 minutes each, then a good cool-down in-between. We've designed a cooling system that uses a Sullivan Streamer 6-12 volt fuel pump, gallon of water (or just draw water out of the lake with a filter on the end of the tubing), then hook the other end up to the brass, water pick-up tube. With a ''T'' fitting, can cool our two boats down at one time. Run a 2-cell lipo and you get a nice cool-down following a run. We can meter down the volume of water being pumped with a small fuel-line clamp, so there should be no fear of shock-cooling the cylinder down. I'll get some pictures this weekend.
You can really tell the difference between the two and three blade props. Just by estimate, the three blade takes a little longer to get up to speed, but it's at least 25% faster on the the water. Of course, we're not running ours full out, nor are the engines leaned for max performance. Still a lot of break-in to go and we're not going to do any serious racing. Running ''formation'' with boats is about as tough as flying formation with RC airplanes.
We were able to get three, 8-10 minute runs on one tank of fuel. When we were done, there was about 1/4 tank left in each boat, so we could have probably run the boats for one more 8-10 minute run, but with little reserve. All in all, a fairly successful evening.