05 Volvo closed cooling overheat?

[Dale R. Duffy]

Brother in-law has a 2005 34' chapparel with twin 5.0L Volvo Penta composite drives. He's had nothing but problems with the drives. The pins keep falling out and in doing so, trashed the starboard drive. After the replacement drive was installed he now has an overheat issue going on with the starboard motor. If he hits the throttle only and gives it some throttle chops it will pump and will be fine the rest of the day. If he just fires it up after sitting on the lift all night, it will overheat and then he has to go back to the throttle chops. Any ideas why this would happen?