I've got 70hp on mine. Actually the engine is a 2-stroke Tohatsu MC60C tweaked to 70hp, weighs in at 118kg. M60 and M70 engines are identical apart from some tweaks to throttle and advance stop.
Top end speed isn't important to me, its overall low end grunt and cruising speed. It will achieve 30mph, two up with trim out slightly and 60 litres of fuel and usual kit on board, tender and 4hp auxilliary engine. Currently has 17 pitch stainless steel propeller. There is a whole argument out there about the benefits of stainless steel propellers on sub 100hp engines. I think it makes a marginal difference only.
A 15 pitch propeller wi give you better hole shot for sure.
If I ever change it, then a Yamaha 70hp 4-stroke would be top of my list.
The transom weight rating is key.