'72 6HP Johnson Help...

I have a '72, 6HP Johnson that has no power under load? I rebuilt carb and the thing idles and throttles up real well....until I put it on the boat and try to go. Did not feel like it was running wide open and was barely pushing my 14ft jon boat. Anyone have any thoughts? Any help would be greatly appreciated.

Compression check?

What was it doing before carb rebuild? Was anything else worked on or done to the motor? Any changes to the linkages or stops? More info helps us help you.

Could still be a fuel issue.