I have a 99 Mercury 2-stroke (40 HP). Starts up instantly and idles fine. The problem is when I give it gas it doesn't want to go. I can only get up to 15 mph even though the throtlle is pegged wide open. I can push the choke in and it will take off as if it going to run normal, but it will slow again. I've had the carbs broken down and cleaned, changed the plugs and installed a new fuel filter. I even drained most of the gas out and put in 93 octane along with Seafoam. Still the same. Any ideas what to do next?

have you had better performance from it before?      what kinda boat are you pushing

Sounds like a fuel delivery problem. First off you won't want to run it for very long like that, if it's running lean on fuel it's running out of oil also. My guess would be the fuel pump, the pulse hose going to it or the primer bulb in the fuel line, if you have someone with you have them squeeze the primer bulb while it's acting up, if it takes off you will know its fuel. You might want to go ahead and replace the fuel line and primer bulb it won't cost too much and they do cause problems from time to time.

sounds like a fuel resrtiction...

if when pushing the choke it clears up and runs...I would check the choke module. ( small round cylinder on the side of the motor with fuel lines and two wires attached). The diaphram in mine was all...cattywampus...and stretched out when I first bought my boat. My boat would start but not stay running unless I held the choke in.

I'm pushing a 17ft. Tracker. When I first got it a year ago it ran fine. Just started acting up. I appreciate the tips. I'll get to working on it right away. Thanks Fellows.