Powerhead Cowl Modifacations for Performance

[olboatman]

This is my take on fresh air.
The stock cover goes over the front hole in the cowl when running.
Sounds killer with the resignation in the box.
Think about the ex chest and how it works.
Now look up resonators and do some reading.
http://www.me.umn.edu/~hork0004/2006-01-3654.pdf
I hate reading SAE papers my self.......................LOL

This is what I'm thinkin of ..... has to be better than suckin in hot air. AirRaid and K&N say their cold air auto systems make more hp. Would need to see dyno proof BUT it makes since considering turbo intercoolers help make big hp.
Gary

[olboatman]

Here is one I modified. I kept the slots high and being cut in the angle of the cowl does create some what of a ram effect. I glassed up the rear handle because some cowls will suck in water from the spray, and I wanted it more air tight.

Attachment 394839

Paul being a Finish carpenter originally(I'm finished all right) I'm curious as to what tool(s) did ya use to cut the slots. I've been usin a Fein Multi Tool to hack at mine....I did an old 25hp yrs ago (louvers) with it but I'm always lookin for better and easyer methods.
Thanks Gary

[racervboat]

Gary or a rotozip with fine blade?

[Forkin' Crazy]

Ram air is fine, unless you are directing it down the carb throats.

[spybot]

Ram air is fine, unless you are directing it down the carb throats.

So if you force air into the cowling but not down the carbs thuis is a good thing ?

[olboatman]

Yes
If the air is forced into the cowl it should not be plumbed tight to the carbs(injection) so to force open the reeds. Allowing the intake to only draw fresh air from outside the cowl is an upgrade from stock.
Gary

[spybot]

So if i add an intake like this
And open up the handle at the back of the cowling like so
This will allow fresh cold air but at the same time blow the hot air out
Any thoughts on this ?
the other options is to have the scoop vertical on the front facing down and have 2 slats cut just at the back of the air silencer
Thoughts please guys

[olboatman]

What you show in the two pics is where I am goin with my 140 OMC. I cut a hole in the cowl in front of the carbs, added a plate about an inch off the hole to break the air flow and keep out water. Also I opened up the hole under the rear handle that I tipped up so to act as a venturi to suck air out the rear. When I get the cowl back from the vinyl shop I'll post some pics with the rest of the project.
Gary

[racervboat]

spybot gary is not using a front plastic cover in front of carbs just like my motor.

[spybot]

spybot gary is not using a front plastic cover in front of carbs just like my motor.

So the black plastic cover that is screwed to the aluminium plate is taken off ?
That would leave the 4 barrels of the carbs left open ???
The plastic part is circled red. This part will be removed ?
Andy

[spybot]

What you show in the two pics is where I am goin with my 140 OMC. I cut a hole in the cowl in front of the carbs, added a plate about an inch off the hole to break the air flow and keep out water. Also I opened up the hole under the rear handle that I tipped up so to act as a venturi to suck air out the rear. When I get the cowl back from the vinyl shop I'll post some pics with the rest of the project.
Gary

Look forward to see it Gary
Andy

[racervboat]

Yes and the alum casting is cut down around the carbs except the two mounts that hold throttle and shift cables.

[spybot]

Go it. Is there any gauze or mesh over the throats or the alu thats left ?
Is it just plain ?
Andy

[racervboat]

just plain,but were not running the boat down a dirt road LOL

[spybot]

Thats true but over here at every loch we have a small fly called a midge pronounced mid-gee

https://en.wikipedia.org/wiki/Highland_midge

They are a total p.i.t.a. They attack in swarms. Not nice especially if you drive through them
They bite like hell and love the taste of blood.
I may think about some sort of gauze.
Andy