Thought it about time i updated the thread. The first attempt at powering the boat didn't go well, mainly due to me not really listening to the advice given on here.
I was fortunale to find a second hand turnigy 35 amp marine esc that someone had bought but never used. I used a small 2100kva outrunner the I was given by a friend. It was originally for a 'foamie' aircraft & was very small. It seemed to lack the torque required to drive the boat at a reasonable speed.
I changed it for the motor HS93 recommended, but this time the boat would get on the plane & then the esc would cut out. presumably because the bec circuit was lacking volts. Further investigation showed that the old ni cads i was using were past their best & although they would seem to charge OK, as soon as they were put on load they dropped voltage quickly.
A new pack of 6 4500mah ni mh were installed, & the boat tried again. WOW what a difference !!! It hurtled across the lake much faster than i had expected. The shaft is a m2 thread, which limits the props easily available. This first run was made using a Graupner 30mm 3 blade prop which has a very low pitch, but still gave a very good turn of speed. The only other prop i had was a 24mm very coarse pitch, runs with this prop were exciting, but not without problems.
with the 24 mm prop the boat 'blew away club 500 racer in a straight line, but the boat sat at an angle due to the torque reaction & would have turned over if i had applied full rudder to starboard. Also it porpoised when running flat out. Run times were surprisingly long, around 25 Min's flat out, with the motor & esc only getting slightly warm
I think the prop answer is somewhere in the middle of these 2 sizes, I'm thinking propshop 3 blade 30 mm should do the trick.
Many thanks to all who suggested motors etc, i really didn't know where to start with this one.
I had better get the model finished now !!
Cheers Glenn.