Hi and thanks for your kind responses. I think I need a 15 X 12 (Volvo PN: 21381264) or 15 X 13 (Volvo PN: 21381265) 3 bladed prop.
I intend to err towards bigger / more pitch as I do feel the current prop isn’t loading the engine.
Does anyone have a suitable S/H prop or know where I could get a good deal on a new one. I don’t want to spend £300 on an experiment…