Re: Motor bogs down in gear
It could be.....
Poor compression in one or more cylinder
Weak or mis-timed spark in one or more cylinder
Poor crankcase pressure/vacuum
Poor fuel supply or atomization in one or more carb
Poor fuel supply to the engine
It takes
Compression, fuel, and spark to make an engine run. Any deviance from correct amounts of each at the right time, could cause the issue you describe.
Excuse my ignorance but I do not know off the top of my head which exact configuration, or actual manufacturer made your motor.
Some motors may have had issues with some parts of the ignition systems which could only be tested with unique test equipment, using specified procedures available pretty much only in the actual service manuals.
Many times a problem as you describe might be fuel related, sometimes as easily corrected as an adjustment to the idle mixture screws.
Perhaps the easiest tests I would make would be to squeeze the primer bulb a bit when it's on the water not quite running well, and see if it straightens out. If it did I would suspect fuel delivery to the carbs.
I would do a compression test out of the water and if any cylinder was more than 15% lower than the others, I would stop there and consider it a major mechanical issue.
I'd try that idle mixture adjustment thing.
I'd try to figure out how many, or which cylinders are actually running and look at the ones that probably aren't.
Perhaps a carb tear-down, clean, and re-assemble.
These are just the "basic" directions I'd head with any motor having issues as you describe.
Also note that if there is, or was a fuel supply issue due (in part) to old, or contaminated fuels, I'd be sure I didn't try running it on that supply after corrective repairs have been made.
It would only lead it to act up again, what with the statement being made "it can't be that again, I just had that done"
