I have a 1996 502 mpi, the hose running from the front of intake is plugged. It looks like it should be running to the pcv but the hose is plugged with a bolt. Is it ok to just leave it plugged and run breathers or put the pcv back in it?

Engines need a pcv to actively breath and scavenge air. Just having breathers isn't enough. I would pull the bolt out and run the pcv.

the OEM stock MPI - 502 for 1996 off the top of my head - One valve cover should have a grommet with a baffle breather and that hose connects to the flame arrestor / throttle body area

The other side valve cover should have a grommet and PCV valve with a hose connect to it So what is in your valve covers ? No PVC valve and no baffle breather ?

Also it would be helpful to post your engine serial to be able to figure exactly what set up you have. 1996 was the trans year from VST fuel system to Cool fuel GEN 2 fuel system.

All OEM stock marine engine set ups, systems, parts and service procedures go by the engine serial number for the engine side of things. Year of the hull means nothing.

Some one put a bolt in a hose in the front of the intake ? are you referring to the water circ pump by pass hose ?

I always run a real pcv system. Screw that hose to the flame arrestor crap.

How do you run yours?

Just has a breather on each side. Just wanted to make sure the hose that was plugged should go to the PCV.

What does the hose hook to on the intake?

Lucky enough for me I use after market carbs and even when the baseplate is not drilled for a PCV the casting for the port is almost always there and is simple to drill out. Then it is as simple as a air breather oil cap in one valve cover and the PCV valve in the other, hooked to carb base. I wouldn't run it to the intake (unless it was a tall and the port was just under where the carb mounts) because no matter what port you run it into it will off balance that intake runner.