Holy crap, don't tell me I've overthought the problem. I've assumed there was an issue due to the fact that the engine revved so hard at full throttle.
My old man bought a Victa Silver Streak in 1980 (I think) and I just used it as a comparison. That old beast is always used at full throttle and doesn't rev as hard as this one.
I'm not entirely sure I haven't already tried that but will get onto it when this bloody weather improves a bit.
Thanks.
