On how to make a plug of some sorts for washing or when it rains... Im afraid the water will be an issue.. waves coming over are also an issue.. maybe a custom rubber plug??

How about a Sunbrella cover for each side with snaps..that's really all you need and it would look good as well. It would be easy to get on and of and fold up to stow away. If you wanted something super trick you could have the Cigarette Logo put in each one.

How about something like this Dan. Make a template close to the size of the hole, just slightly larger. Have your guy cut them out, then glue foam to them. The foam will keep them snug enough so they don't fall out while sitting at the dock or the beach. Just need to remember to remove them so they don't blow out when running

I like that idea, Joe! I think we talked about it before but I have a short memory! haha

I have seen a few race boats with flaps that cover holes at rest and then when running, the in flow of air the the engine compartment lifts then up to let the extra air out. I assume you have similar cut outs on the front side ???? Make some flaps that have a thin rubber/foam seal and you will be golden.

Like these Smitty?

How about some little flaps that are actuated by the throttle cables. When throttles pushed down, flaps open. http://www.youtube.com/watch?v=zVENNZ8jZQM

Or maybe have some alumnium vents fabbed up that look like the ones on your transom

Mild---

Yes something similar, but smaller.

I say combine the two ideas... billet vents but with throttle activated louvers. So to try to explain what's in my head it would look solid at a stop and then when your on the sticks it would open to look like grills. If you gave me the cut out dimensions I could make a solid model.