I took the ASR to the Oxford model boat club's Thursday afternoon session at the pond, and it behaved perfectly. It seemed a little faster, and definitely quieter, but the move forward of the motor by an inch and a half has made very little difference.
I took two 2S 2900 mah lipos, changed them over after about 90 minutes on the water.
Sometimes it is hard to beat a good simple boat that simply works as it should.

Following the submerged branch incident last Sunday, the broken coupling has been removed (that was the easy part!) and the motor mount prised way from its original position and fixed in place about 1 1/2" further forward (that was the difficult part!) in order to be able to use a Huco double coupling.
All installed, runs smoothly, and the current draw when coupled to the shaft is about one amp more than the motor on its own.
Weather permitting, it'll be back on the water tomorrow.

I took the ASR out to the local club in Oxford last Sunday and, unfortunately, hit a submerged branch which broke the coupling between motor and prop shaft.
I changed the broken component that evening, a fairly tricky operation as it required the motor to be removed, and there isn't much room for tools and fingers in that hull.
Having changed the coupling and replaced the motor in the boat, I started to think that the coupling broke rather easily, so removed the motor again this evening, carefully cut away the motor mount (managed to get it out without damaging the thin GRP hull), so tomorrow will glass in a new motor mount about 1 1/2" further forward to allow me to use a more substantial coupling. It will also move the c/g further forward, which will help as it sits a little stern heavy in the water.
Next club day is Thursday, but I am visiting my daughter & granddaughter tomorrow, so might be taking a different boat out on Thursday, unless I have time to put the new mount in tomorrow evening.

Thirty plus years ago I built a British Power Boats co. Motor Gun Boat from the Dean's Marine kit, and sailed it all around the south of England at various shows. I sadly sold it when I was moving abroad, but never forgot the great little boat.

Last December, I was shown a Dean's 63ft ASR (same hull as the MGB both in model and full size versions) which the oxford model boat club was selling as it had been donated in order to help the club raise funds.

The motor (540), ESC and rudder servo plus Tx & Rx were removed by another member of the club and a little money changed hands.

Got it home, and started working on it. Obviously, I needed to replace the drive and radio components, as the prop shaft and stern tube simply fell out when I picked it up - I think it was held in mainly by the motor coupling!

The coaming around the deck edge had definitely seen better days and was held together but patches of plasticard. I moved the entire coaming and replaced it, with a light wooden strip to help it sit against the edge of the deck.

I then turned my attention to the stern tube. I had a spare of the same size (bought a while ago from Steve at Model Boat Bits) and set about removing the mass of filler that was intended to hold it in place. Once the filler was removed, a rather large hole was revealed.

At this point, I visited Dean's Marine for their Christmas open day and bought a second MGB kit, as I still wanted to replace my old one and also because the dimensions for mounting the prop shaft, etc. were the same for both the MGB & the ASR.

I have followed Ron Dean's advice and added an inner stern tube support as a precaution. Just a piece of 1/8th ply held in place with microballons and cyano.

Two months or so later, I now have the ASR hull ready for the final placement of the battery tray & radio gear, which shouldn't take long. I will then make a start on its sibling the MGB.