Mercury 500 bogging down and dying under load?

[Sacky661530]

Hey guys I just took my boat out for the first time since I got it. It's a 1965 alumacraft 16ft. Anyways it has a 1973 Mercury 500 thunderbolt ignition 50hp. So it seemed to be running just fine crusing around the lake , but it was super slow almost like it had a govener on or something. So I adjusted the trim and it was a little better. But then I would slowly get up to speed and it kept dying out on me every time I got to where it sounded top speed it would bogging down and die. So I'd start it back up and try 30 times to get it going but every time I put it in gear it would die. So I just towed it back to shore. It was getting gas and all that so any suggestion would be great

 

[Tassie 1]

Have a read through the stickies at the top here and at the start of the engine repair page.

Do all usual checks,
compression
fuel
spark