When i freshened/upgraded my motor this year i had a reversion problem with my lightning headers w/captains call. I replaced exhaust system with stainless marine hi torque 3 manifolds and 5"tails.You could hold your hand on the lightning headers after sustained wot and they weren't probably 130 dgerees,these high torque 3's get HOT,even at idle. I have already burned my arm on them so without actually measuring them i would guess the surface temp is over 200 degrees.They have a ton of water coming thru exhaust tips so it's not a water flow problem,i just think the water jackets are close to internal manifold and that they by design just run real hot. My problem is my underhatch temp is also dramaticly higher and my procharger air intake literally sucks right off the hot manifold surface. When i open hatch after running hard you get a blast of heat from engine compartment,the blower is so hot you can't touch it,even the innercooler is warm on the outside and it never was before these manifolds. My boat is a baja 272 and it has some typcal bilge blowers that pull air in and out under a cowl behind engine hatch,running them makes no difference in the engine compt temp,these new manifolds are like giant radiant heaters!! Rm builder suggested installing a couple of "NACA DUCTS",they are the wedge shaped air inlets you see on aircraft and some sports cars. Has any one installed these on their boat,what is the ideal location? My boat has a real round hull above the rubrail where upper and lower hull meet so it would be difficult to mount one up there unless i got tiny ones. I don't think it would be a good idea to mount them below the rubrail/seam as it is too close to the water line. Boatersworld sells white plastic louvers that are approx 2 1/2 inches wide by 10 or 12 inches long that i colud also cut in. Ive seen boats from the 80's with the vents similar to that mounted down the sides of engine compartment. Without being ducted to blower inlet does anyone think it would make any real difference?Thanks for anyones experience or input that has added vents to their boat,good or bad,please post,Smitty

I know a guy that will custom make anything you want out of fiberglass/gelcoat if you're interested. It might cost a little more, but you'll get whatever you want. He made the one's for my Cig..

Fred, Whats the prices on the vents?

Smitty,

A good way to check is to crack the engine hatch open when you are running at speed, However make sure you run a tiedown strap across the hatch to make sure the wind doesn't rip it off, maybe from the ski hook to the seat frame.

I have 3 stainless louvres directing air into the engine compartment and one out. 2 on each side.

Have you contacted your exhaust supplier regarding the high exhaust temps, that doesn't sound right.

My boat had one on each side origionally, but found that raising hatch a couple of inches picked me up 200rpm so I added two more. They came from boat us or west marine.

Only downside is that they are easy to ding on some docks.

My biggest problem i'm trying to solve is the supercharger air horn is drawing air acrosed a real hot manifold raising my intake air temp signifigantly. The air horn is so tight to the manifold i had to cut 1 inch off the blower snout and trim 1/5th of the air inlet screen off the bottom to get it to fit at all so putting any kind of bend on it to pull air from somewhere else is out of the question.My boat doesn't have any flat areas above rubrail to really mount a naca duct without loooking real cobbled,i was thinking one on each side with a 3" duct directed to the manifolds would do it. I'm thinking a couple of louvered ducts above the rubrail are probably the best i can do without cutting engine hatch and putting a scoop on it but keep the ideas coming because maybe theres something I'm overlooking,Smitty

getting air out is just as important.... think about venting the back too...

Neat...

Nice nail polish you got there Sean

this coming from the guy that had me fill in all the ducts on his boat

i think it runs cooler now than it used too....