I know that in cars, the "ram air" effect does not start until 100+ mph. Before that, its just cold air induction.

I would say as long as you have cool air flooding the engine compartment you will be fine. I'm not sure if there is much of a gain past 100 either. Someone else here should know, and you can calculate it pretty easy also if you wanted to see how much pressure difference you would get.

I've built a new hatch with two scoops for my old boat. The scoops were locally made [ similar to Harwoods ] and I cut them down for low profile look. Cut the ends off too , so the air flows right through .I have stainless screens in the intake and the rear oulet to keep any critters out . The ambient temperature is at least 20 degrees cooler in the engine bay now.Here are some pictures .
http://www3.telus.net/spectrasonly/Scoop%201
http://www3.telus.net/spectrasonly/Scoop%20project%202
http://www3.telus.net/spectrasonly/Scoop%20project%203

We have a ZZ 572 in my friend's boat we put together 2 years ago . The engine is covered with an engine box inside the enclosed cabin .
We've installed a similar scoop on top of the cabin and air directed thruogh a duct .The temperature is a constant 72 degrees inside the engine bay at WOT .
http://www3.telus.net/spectrasonly/IMG_1858.jpg
http://www3.telus.net/spectrasonly/c...20interior%201

WHAT kind of boat is that?? I love the headers and the teak...

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Originally Posted by Scott B (Post 2289775)

WHAT kind of boat is that?? I love the headers and the teak...

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A one of kind , not for production. . My friend built the entire boat in 3 yrs, including the mold . He destroyed the mold afterwards. The boat is 33' , foam cored hull and weighs at 6000 lbs rigged . We had her up to 65 mph on GPS .
He's in the process of painting the hull sides blue and some simple trim colour. The wood inside is actually mahogany , and the headers are dry Stellings . He did the inside finishing on 'Status Quo' when he worked for Sovereign [ now Richmond Yachts] http://www.richmondyachts.com/gallery.html
I've been on 'Sun Chaser' to check it out while it was being finished, and it's one nice yacht too .
Here's a test run of Craig's boat from 2 yrs ago http://media.putfile.com/Craig-pushes-the-stick