I used to have an old 7hp single
in the ferro
Hartley RORC 32' that I built.
7 hp powered a 7 tonne boat along very nicely.
I didn't notice any wealthy nobs in their overpowered plastic surging past.
10hp should be plenty for your boat. I would suspect a combination of folding prop in poor condition and incorrect pitch/diameter for your boat and sailing conditions.
It sounds like you want your power to be available in some pretty specific conditions.
I would suggest clearly defining those conditions, getting the gearbox
ratio and power/torque curves (I found this on the internet - there are others
) for your engine/gearbox (not to mention the model/serial numbers) and then discussing what is needed with your local (recommended) prop shop.
I note that the 10hp for the Bukh
is a continuous rating so it may be possible to load it up.
If your boat is coming out of the water I would check that the folding prop is functioning correctly and measure the diameter and pitch.