The original install on mine was really bad. There were 4 blowers running through clothes drier vent hose. The hose wound all over the place and was partially crushed is a number of spots. Very minimal flow. I redid the 4" drier hose with 5" fiberglass exhaust pipe and sweep exhaust rubber 90s. It goes though the rear engine room bulkhead near the ceiling, along the ceiling of the lazarette, and out through the transom below the swim platform. There is a water block where the pipe turns up in the hollow transom, going most of the way to the cap rail. The blower mounts to the 5" pipe with a 4" to 5" flexible coupling which eliminates vibration. The purpose of the 5" pipe (over 4") is to eliminate frictional line loss. It is amazing how well it works! The one blower produces more flow than the previous 4. You can see ripples on the water out to 2' from the force of the air coming out of the blower. The blower is worth 10 to 15 degree temperature reduction in the engine room measured at the ceiling. So far, temperatures have stayed below 100 degrees with the ventilation on. Outside air tracks into the engine room through the hollow keel and rises in front of the engine.
Blower (yellow fan blades) going through stern engine room bulkhead.
Blower pipe exiting transom on port side under swim platform. Engine exhausts is on the starboard. The water block goes above the rub rail before turning back down.