Many thanks Scorcher

On the spreadsheet you have kindly supplied does ‘datum’ mean year of manufacture do you think?
I think my boat is a bit too old for the spreadsheet you have supplied.
My boat is a B 38, not a ‘match’. It is the rear cockpit cruiser that is everywhere, not centre cockpit, not ‘sporty’.

My engine and saildrive don’t match the data in the spreadsheet.
My spec:
Engine MD2030 – D
Leg MS25S, ratio 2.47:1. Also known as a Volvo 120 I believe.

However I do note that boats in the spreadsheet with the same spec engine and leg have a prop larger than 15″ Dia. This lends credence to my feeling that the boat is ‘underpropped’.

Can anyone add anything to this? I need to replace my existing, rather tired prop soon. I will also be throwing the Stripper rope cutter away as it is damaging the leg where it locates on the Allen head fixings.