low power from 2000 25hp merc outboard

I just had my 2000 Mercury 25HP outboard serviced after it sat up for 2 years. The shop cleaned and rebuilt the carb and replaced plugs among a few other things. It now starts great and idles smoothly. It runs very smooth until I try to get it up on plane. It struggles to get up and feels like it only has about half the power it used to. It used to push my boat at about 28MPH with 2 people in it and always jumped on plane right away.

The mechanic thinks it may be the switch box (power pack?). Any suggestions out there? Does that seem reasonable? Or should I check something else before buying a new one?

Re: low power from 25 merc outboard

It could be the box or one of your coils. Next time it does this, let it do it for a minute then immediately shut her off and pull both plugs. If one is hot and the other cold and wet, that's your problem.

Jeff

PS: I've seen several bad coils lately. Assuming one of yours is bad, you can swap the green wires to the coils AND the spark plug wires, then see if the problem moves to the other cylinder. If so, it's the coil. If not, it's the blackbox.