I have a late 1980's model 60hp Johnson ob (on an 18' boat) with a problem
that I hope someone can help me make sense of.

It was running fine at the end of the season, but wasn't charging the
battery, so over the winter I took it to a shop that determined the
rectifier was bad. They replaced the rectifier, which corrected the charging
problem, but then the engine wouldn't open up under a load--well before the
boat could get on a plane, the motor would bog down and die. Using the
"neutral throttle" the motor would rev up like normal.

Back to the same shop, where they said the carbs needed to be rebuilt, which
they did. Back in the water, same story, engine bogs down under a load. But
then I noticed a ringing rattle under the cover, and found the flywheel nut
loose; I could remove it with my fingers.

Back to the shop, and now they say the shifter is not able to open the
throttle when in gear. They put on a new shifter, but it has made no
difference, it still bogs down.

I believe coincidences are rare. My suspicion is that when they worked on
the charging problem, they removed the flywheel (am I correct to assume this
would be done?) and never tightened it afterwards. Would a loose flywheel
cause the problem I've experienced? Could running with the flywheel loose
damage the fit where it can't be tightened properly, and the problem
continues? I suppose they could have screwed up the carbs when they put kits
in, but the performance of the engine didn't change any so I don't think
that's it.

Am I off base here? Any ideas?

Thanks for any suggestions.