I know this forum isn't for this type of boat, but some of the people on here know the Gen IV big blocks better than anyone.
My brother has a boat with twin 454's that vapor lock after sitting for about 30 minutes to an hour. The boat has forced ventilation through two blowers and adding extra ventilation would be very difficult without hurting the looks of the boat.
The engines are stock 1998 Mercruiser MPI inboards.
Any suggestions on how the vapor lock can be prevented or removed easily? If possible, he would prefer to not open the engine hatch which is also the floor.
Thanks in advance for any insight you can offer.