I did much the same on our '91 30T. I mounted two blowers, one intake and one exhaust and put the intake and outlet vents on the sides of the walk thru transom. My batteries were in the aft seat lockers so I didn't want to heat the lockers. We ran the blowers when motoring and for a while after getting back to the slip. Helped especially when we would turn the air conditioner on. The rule blowers were mounted in the two aft seat lockers. I used two blowers because I found it easier to run 1.5 inch flexible corrugated tubing out of the engine compartment, under the aft berth decking, thru the bulk head, then up past the fuel tank and into the lockers. I seem to recall the 3" vent was going to be a real challenge so I adapted the 3" rule blowers with pvc fittings to fit the 1.5" vent tubing. I used 3" tubing to the vents in the walkthrough and added a "riser" loop that would keep water out of the tubing and blower in following seas if a wave were to have washed over the walk thru transom (not likely, but was easy to do). That restriction is why I decided to use an inlet and outlet vents. Cool air was forced in and hot air sucked out. Both vent pipes ran by the prop shaft and up into the engine compartment. The suction pipe went to the top of the compartment to get the heat and the cool air inlet stopped just above the tranny. I probably should have run the cool air blower pipe right to the back of the Balmar alternator to cool it better. I'm considering adding a second blower to our h36 just like Nick said above to bring cool air in as well. PM me if you want photos or more detail.
Ralph, the engine cover is awesome...looks like it gives lots of access when removed.
Dan