Naca Scoops For Opti Engines
 

For those running Opti power 250 -300 you should be aware that @ high speeds there is a Vacuum that is created on rear of engines and have seen video of mist getting drawn into air intake which is on rear of cowl . You might not think its a problem inhaling mist and maybe fresh water is maybe Ok but if you run an OPTi in salt you should be aware that your Powerhead is getting misted with corrosive salt water . Simon Motorsports recommend that a front intake is installed to break vacuum .

I manufacture several marine related items and in final tooling stages for pair of super sleek recessed ABS plastic molded NACA ducts that drop in on upper right and left of cowl on the angled section . Will keep uptaded
HERE IS YOUTUBE VIDEO :http://www.youtube.com/watch?v=Zfx6l...layer_embeddedhttp://www.youtube.com/watch?v=sV3Zo...layer_embedded

hey larry, can you come up with a naca duct to fill in the side scoops on my 36 skater? I called Skater about it and Peter doesnt have anything

Good idea,How big are the vents?

I was having the same problems with my 300XS on my 28,motors looked like rock candy after a few hrs run in the ocean.I had Shaun Torrente install popet water diverters,most of the water dumps out the side.Motors seem to be staying dry now.I would like to see what you come up with though,Motors can't be too dry:drink:

I made these NACA ducts for my old race boat and still have the mold .

As far as OPtI my new NACA ducts will be better @ force feeding fresh air very close to intake

Larry,

I am also interested to see what you come up with.

Frank ,

No problem will have tooling done this week . Anyone with an Opti is going to want a set , they are sleek and will srop in with small lip with doublle sided 3 M tape .

Here a few pics of the first ones out of mold . They are ABS plastic in will com with doulble sided 3M tape and template . A must have for anyone running an Optimax. The area in which these drop in has a complex curve and these will fit like a glove . I have many hours in tooling to insure fit

Where on the cowling do these mount?
Would there be 2 per cowling?

Yes two and they will be located in upper front section of cowl area that is angled

Larry,
Can you paint to match? Is the surface smooth? How much?
Curious on the dimension of the opening and if it is enough to provide additonal airflow besides eliminating vacuum. I have a pair of 3.0l's years back with heads/brucato intakes etc and the boat was 3mph faster with the cowling off. We did some mods and gained 2mph but never got the full 3mph.
I would be willing to take a look at a set. Send a pm with the info.
Thanks

Larry,

I have the same question as 'Double Rigged' above.

Ok they are made from ABS plastic and one side has a fine texture and the other is smooth . I was planning on offering them with texture out which will closely match the rear vent texture , but I suppose I could make them for you smooth side out . They dont recommend painting ABS but if you know what you doing ( scuff pad , adheasion promoter ) you will be fine .
Dont have any Data and will never claim HP gain ! That said the opening is 2.5 " x 3/8 " and any engine on planet will run better with direct cool air Vs ais being drawn in over hot engine prior to being injested . I may offer @ extra charge pair painted black

For those of you who dont like my NACA ducts here is an option !!! Grabbed pic from S&F , who in their right mind would do this

How waterproof are these? Spray or rain water won't get in ?

Bill,

How are you doing? Been enjoying your Skater?

Larry is a very talented guy, and is really on to something
here, in relieving the vacuum from the rear intake, which
ingests the spray. As a side benefit, we should get cooler
air going into the engine, and that is always a good thing.
I am very interested, but will probably keep them covered
when the boat is not in use. Here in FL, it rains like a
monsoon during the summer.

As far as spray, I would rather get occasional spray from
the front, than continuous spray from the back.

I am sure Larry will check all of this out, and let us know.

Thank you Frabk for that !! This is the first one from mold and I think I can bridge the rear of opening and open the slots to wrap around curved area .

Larry

Bigger is better. I do not think water from the front is a problem. My vote would be for a painted finished look to match the cowling. Would be willing to pay extra for it. As far as rain goes when in use a little fresh water to rinse/wash the motor not a bad thing boating in salt water. Saves cleaning the motor LOL.
I keep my motors covered when not in use.
Would love to try some. When can you ship?

Will keep you all posted , 2 weeks or so . They look simple , but I have many hours in tooling and after pulled from mold I have to trim by hand , install 3M double sided tape .

Looks like an AC vent for a small cruiser,I would NOT have that crap on my cowl.I imagine driving in the rain,would ingestion water the air intake:eek:

Watching closely! looks like a great idea bro!

I agree !!! But you already are injesting water 100 % of the time !!! Check this out http://www.youtube.com/watch?v=Zfx6l...layer_embedded


I often ponder if Mercury hires Chimps to engineer their engines ??? How in the hell could they overlook this ??

Just finished up 2nd prototype , this one has improved air flow as slot is much longer and painting it will be an option The Naca Opti duxt on left is my first prototype with air slot on rear . As you can see in the other Photos the slot wraps around the side which should be all the air it needs . Each engine will have two dropped in the upper R & L front angled section on cowl

Looks great on the painted one. How much and when can I get 4.

Not sure on pricing , will keep posted when they are released . The painted ones are much more work as they have to be prepped , adhesion promoter and then straight up black Urethane . NOT A MICKEY MOUSE SPRAY JOB !!!

Larry

ss screens to stop the direct spray ?? those are nice ,I am interested. Maybe only mount 1 vent on the inside side of each cowling?

They are not flat , highy complex curve and will only fit as shown . Keep in mind as of right now your engine is inhaling water 100 % of the time so that one time you get a splash is really no big deal. I shoild have a pic of them in place later today. Each set will come with template and you simply tape cowl to protect from scratching and use a roto zip

Larry, any chance I could get four sets of your scoops?

Been hard at work on thses scoops and here is what they look like installed . They come painted gloss black Urethane , have 3M emblem double-sided tape , instructions and Template . They will be on Ebay very soon

more pics

these came out really nice Larry, and the colour blends nicely too!

I will need 2 sets also

The Naca ducts look nice.I had Shaun Torrente install the popet water diverter on my motors.The water dumps out the side,No more water on the engine,and with the new tuner ,lightened flywheels,motors sound like 2.5s. When I picked up my skater from STR,took it to Sanibel & ran my Skater for 2weeks in the Gulf.No water at All,checked the cowlings daily.Before STR......, water in drives,on motors,top speed 105.Now.....No water in drives,no water on motors......cruise at 5,000 90 - 92mph WOT 6,300 115+ Thanks again for the referall to STR!

I just took delivery on my 375 HP EFI strokers . I have heard from many people including Dav Bush that the Opti will pick-up 2-3 MPH with coel removed proving that the stock rear entry air inlet is restrictive and my scopps will deliver cool fresh air right next Plenum

I dont know how restrictive it is,as a stock motor Sucks spray in.2-3mph is huge,since I actually Run my boat I will try it and let you know.I would not run like,that daily.... I am NOT Knocking your ducts you did a great job,looks factory,just letting people know there are other options,that add HP and stop the spray.Shaun told me your motors are 350 not 375....My 300XS came in about 335 according to Shaun.

I have since decided to go with pair STR 4 inch throttle body , should be well above 350 hp . Only running these for a season an then swapping in pair Opti powerheads

Offshore Steve, just curious do you have any air mods to your cowlings or are they stock?

Those should work well.Shaun wanted me to wait till I had put some time on the current mods for a baseline.Larry ,I wish I had your Tallent,what you have done with that old 32 is Amazing!!Cant wait to see the performance#s,when do you plan on splashing her?

Thank you !! I'm hoping this spring but to be honest I'm very tired and out of money .

Larry

Yes I heavily modified.........I pulled out the top insulation:drink: No seriously the popet water diverters stoped the water on the motors for me & it looks cool when you take off and it throws large stream of water to port and starboard of the boat.I will install the Larry Naca Ducts as well,cant have too much AIR!