At last some activity on this one. I thought I'd better measure the wriggly amps so I can work out what to ask my electrical advisor and ESC supplier for. At the first try both motors wired in parallel were pulling 810mA, on the bench with no load. This seems like quite a lot to me - 4/5 of an amp just to turn the things over! The shafts felt fairly stiff so I thought I'd try a bit of running in, out of the water, with plenty of lubricant and checking for local heating quite often. After flattening the battery, I got 740mA on both motors, 370 on the port engine and 400 on the stbd. This still semed quite a lot - while I was investigating the shafts I discovered that there was no end float at all on the port, and only a smidgeon on the stbd one. I therefore stripped the motors out in turn, to show the UJs as pictured below. With the motors out, both shafts had a 1/4" or so end float, and the motors had about as much as motors usually seem to have. The socket part of the UJ is pushed right on the the motor shaft, so that the end of the ball is touching the end of it. I shaved a bit off the end of both balls with a scalpel, and reassembled things. Both shafts now had some end float and a bit more running gave me 600mA in parallel, 260 port and 290 stbd. So we seem to be making progress - I'll try a bit more dry running and see if the figures go down much more before I try running under load. There is loads of side play in the shaft outboard end bearing, so that's never been tight, but I don't know what happens in the inboard one, and I don't really want to disassemble it. I wonder if there's an O ring in there - has anybody had a look?
Is anybody out there finding any of this in the slightest bit interesting?