Engine Compartment Ventilation

[Turbojack]

I did search & here is thread that has a picture of naca on boat (last picture in thread)

naca

It would be nice to have one made out of metal to fit on side of hull. This would be way better that the other vents out.

As to 130 air temp. I have good friend that works for big engine company (2000+hp) as a trouble shooter. He was telling me that they have their computers programed to shut the engine down when air temp gets to 130 Said they can not build any kind of HP when air temp gets that high.

If you get your hands on a K&N Catalogue they have a dual snorkel intake made to sit on top of a Holley. You could run some duct work from the snorkels to an outside air source. This is not Coast Guard approved however. The intake planum is not on their website, only in the catalogue

[Smitty]

I have a K&N catalog and I looked at the one they list and in IMHO it doesn't look big enough to flow the right amount of air for a big block engine in a boat application. I need even more airflow because I run a supercharger.

I did look at the ram air boxes and that looks to be alot bigger and it all depends on how much room you have around carb as far as diameter and height. I am restricted to 4" above carb due to engine package height because I will not cut hatch.

I am going to build a custom box this winter out of aluminum and feed air to it via 2 or 4 NACA ducts that I am going to graft into the sides of my boat. I just need to figure out my max CFM that the engine draws and then design a system that can provide 25% more flow than max demand.I will post photos when I am completed.

Dave

For the economy minded do-it-your-selfers who need a water manometer to measure compartment pressure it is easy to make one. Take 1/4" clear plastic tubing and attach it in a "U" shaped pattern to a vertical flat surface or board. Add a ruler or marks at 1" or increments. If you want to get fancy put coloring in the water or use any liquid with a specific gravity of 1.0

You can also beg, barrow or steal manometers from oil burner service people who have them.

[ThirdBird]

Interesting thread here. I also have thought much about this issue. As others have said above, I really don't want to hack holes in my boat for additional vents but, somebody mentioned adding ventillation from the cockpit to the engine bay. That sounds pretty do-able and it won't show. As others have said, it gets pretty damn hot in there especially when shut down.

Good info here guys, keep it up! Best boat site on the web.

The vent holes I put in mine are at the rear of the cabin side storage areas. At the rear, I have a removable panel on each side. I cut a 4" round hole using a hole saw in each side. They are not visible unless you stuck your head in my side storage ( you know...where the beer holders and dock lines go). I also have my battery switch mounted back there so I can switch w/o removing seat or anything.

[formula31]

Because I run in the rain and rough water a lot, plus washing the boat, I kept my hoses well away from the carb flame arrestors since I didnt want the carbs eating any water.

[later]

i have a 98 fountain and on the back transom notch fountain has installed 2 two inch through hull fitting and attached hoses reaching to near the tops of the motors, when asked about this as my other fountain did not have this i was told that it does 2 things
1.) it breaks the vacuum created at the notch on the bottom
2.) it pulls hot air out of the engine compartment.

later
dave

[formula31]

Ive heard it works very good at sinking them too. Just kidding.

[Bill272]

I saw a boat this summer out in the bay that addressed this issue. It was a Formula 311 with some big power, I kdon't recall how much but I think 650HP+. Anyway, he put 4 extra vents in the back and then raised his engine hatch for more ventalation. I'll attach a pic. The extra vents are in the black stripe above the rubrail, and he made some taller back hinge brackets to raise the sunpad/hatch. Everything seemed pretty stock until he fired it up...