Help Me Out If You Can 88 Merc Xr2 150

[carpet guy]

Got my boat out for the first time this year due to bad floods
150 has always been hard to start but when I get to sometimes it dies going into gear
takes off like a bat out of hell but out of the blue it bogged down bad and would not let me go full throttle it*
it will stay idle and putz around the lake but out of the blue it takes off good then right back to bogging down
put new plugs,head gaskets,water pump