Yamaha 4 stroke HT
I bought my 26M with the Yamaha 50HP fourstroke. I am not sure what you have now but this unit allows me to cruise comfortably at 15Kn with full ballast and load.
If I dump the ballast ( on the smooth ) this will rise to a good 22Kn.
It also has little effect on sailing as it is substantially less weight than the bigger powerplants. This may be worth considering as you choose.