Need more air in engine compartment 42 lightning
 

Hey guys, I am trying very hard to avoid scoops. I need alot more air in my engine compartment and I dont want to ruin the hatches by cutting them up. If anybody has done mods without scoops, if you can send some pics, it would be greatly appreciated. I have a pair of 1200's + going in and last year when I raised the hatches at 4000 RPM, the AFR meter rose by .5 to .75 which is alot at that RPM so just imagine how much more it would raise at 6000 RPM.. Thats quite a bit... Any other ideas would be great too!

1996 42 lightning
Joe

I'll get some pics this weekend. I'm building new hatches now. My third set, first ones were flat, seconds one scoops now ......you'll see

I removed the back off each of the six vents in the bilge.
Also the triangular vents on each side only had one 5" hole and I added a few more
2" ones. I would think your reading differed with adding more cool air to the bilge.

Please send the pics, I would like to see them

Well exactly, we were adding more cool air to the engines. We did the test repeatedly and it was the same result all 3 times at 4200 RPM's. Plus it responds on the AFR meter in seconds each and every time. That meter was the best investment I could have ever made!

I made some better flowing side vents, you can also duct your speaker holes under back seat directly into engine compartment

Nice vents....got anymore pics?

Also remember that you need to get the air out of the engine compartment too. Add good clean air but vent out equally. Great example to see is the stern of Outerlimits GTX......good luck.

Install a vacuum gage hose next to the engine intake and run out the hatch so you can read it.
Close the hatch and go for a ride.
Is there a vacuum in the engine compartment?
If so then opening up the inlets will help...
But it also could open them up too much and pressurize the engine compartment and force engine room exhaust gasses, (carbon monoxide gas) into the cabin.
The cabin is not perfectly sealed like a car or aircraft where the gasses cant make it back into the cabin.
Be very careful changing intake without increasing the exhaust side of engine compartment air/gasses

I had that problem on my old boat with forward facing scoops. Cabin would smell like fuel/bilge after a run.

I like the idea of adding ports/vents on the back of the transom, like these To help exit some air.