So, your boat was a 575 boat from the start. I wonder why the air is limited. Only reason I can think of is possibly too much air pressurizes the engine bay and puts fumes into the cabin? Maybe Reggie will let us know. It seems like more air would be better to me. Rob, is yours the same as 4bus?

Mine's the same, board comes up and sides have large holes. There's plenty of room for air to get into the bilge.
I've thought about putting vents on the back of the boat to relieve air pressure in the bilge and on the rear of the boat. Kinda like Outerlimit flaps. And building ducts to direct the air flow right to the air cleaners. I started making the ducts and handed my molds to someone to finish. He f#$%@& them up so I never continued.
I've also contemplated ducting and adding small fins ahead of the windshield to lower air pressure and direct air flow. I was set up with an air pressure gauge, red yarn, tape, video camera, and an aeronautics engineer to do it once and blew a head gasket. Never tried since.

I think your air duct set up might be good for 100 rpms pr so. Run your boat with the hatches off or open ( you can strap a couple tiedowns accross it to secure it) I picked up 100 rpms w my last boat , something about plenty off fresh clean air. My boxes are probably the old school ex stlye .. when mine was built the ram air tops were new. Pressurizing is great for na motors but probably not so much with the blown motors. I think directing air to the engine intakes might work for more speed.

Yes, boat is exactly the way it cam from fountain.


I have experimented with running the hatches cracked and it helps, even more so on extremely hot days. The split hatches work great for this :D I get a high pitched whistle from between the hatch cushions when the hatches are closed, which leads me to believe that the holes in the air ducts are not large enough to feed the required cfm to the engines. The whistle goes away with the hatches cracked 1 inch

If you want to know how well true ram air can help a NA motor, just take a look at what sport bikes have been doing the last 15 years.

They offer Ram Air. Not a pressuriozed air box. I have run presurized air boxes before on Superbikes I have raced. Not only do they force air, they also force fuel when it is pressurized. That is the effect of the engine compartment having ram air. It is ram air and fuel like a pressurized air box. Or it is more volume. 1 of the 2.