Working on merc two strokes is fun, super easy to do.I own a 06 25 Yamaha and a 01 Merc 20. Both have been great motors maintenance wise. Regardless, you are going to have to hunt to find one of the 2 strokes in good shape and pay $. It really depends on preference for brand. You have Merc fans an Yamaha fans. They both will serve you well given there not junk when you purchase..
The Merc does seem to have more power than the Yamaha. I have a 25 Yami on my Gladesmen and a 20 Merc on my Gheenoe Classic. The classic will smoke the Gman all day long. Take into consideration, the Yamaha is running a four blade and the Merc is a 3. If the Merc wasn't a long shaft then I would switch no questions asked. The Yamaha has its cold mornings too..Go Black (Merc) and never look back.. For some reason, Merc 25hp 2 strokes put out more power than a Yamaha 25 2 stroke.. I've tested both on my Waterman and there was a noticeable difference with the Merc in terms of torque and top end speed using the same prop..
Merc is 6000 tooIve owned both 25 mercs and yamahas
The merc feels torquier (like it has more power) out of the hole.
But its because of the gear ratios
The yamaha is faster on the top end when put on the same boats and propped accordingly.
I think its vecause on the top end the yamaha has 2 carbs, a slightly smaller gearcase and the better (for top end)
Gear ratio as well as the max rpm is 6000 and the merc is 5600 I belive