I've got a 2003 40 hp Mercury that is giving me fits. Its the 59 ci 3 cylinder 2 -stroke motor.
I've had the reed plate worked over, the reed stops are still in place, but have been bent out it looks like. All the gaskets are good on the front end. Timing is set for maximum advance (I've played with this and haven't gotten any noticeable difference in performance). Has good even compression on all three cylinders at 140 psi exactly. And here's the kicker...it runs great with the stock 40 hp carbs.

However, with the 60 hp carbs, the newer WME- 45 models, top speed and performance is right around 5/8th throttle. If i give it more throttle, I actually see a drop in rpms and speed not a gain like I would expect. I've ran two sets of these carbs with no change. I've went as far as to ship both sets of carbs to a friend who put them on his motor, which is exactly like mine, just 2 years newer, and they ran awesome.

I'm running #62 jets with 87 octane fuel with an oil mix of 50:1 and Chris Carson sport reeds.

I've been dealing with this issue for some time and don't know where to go from here. Very frustrated and need some help.

Thanks