That much condensation means the air in the engine room is quite a bit warmer than the hatch. Any insulation on the inside of the hatch will help, as would some ventilation. I have a storage area in the bow, I threw some wet rope in there once last summer, a week later I opened the hatch and it was still very dank & muggy-- I just propped the hatch open with an old shoe, and by the end of the weekend it had dried out nicely. That's a bit different than cold condensation, but some ventilation will help equalize the air and hatch temp to help prevent the condensation in the first place, and will also allow the moisture to escape.
In the meantime, a $7 tarp from Harbor Freight comes to mind!
1988 SkipperLiner 53x14
1995 Tracker Party Cruiser 32 *for sale*
2003 Chaparral 260 SSI
2000 Allegro Bus 40' DP