• Welcome to the Checkmate Community Forums forums.

    You are currently viewing our boards as a guest which gives you limited access to view most discussions, articles and access to our other FREE features.
    By joining our free community you will be able to:

    » Interact with over 10,000 Checkmate Fanatics from around the world!
    » Post topics and messages
    » Post and view photos
    » Communicate privately with other members
    » Access our extensive gallery of old Checkmate brochures located in our Media Gallery
    » Browse the various pictures in our Checkmate photo gallery

    Registration is fast, simple and absolutely free so please, join our community today!

    If you have any problems with the registration process or your account login, please contact support by clicking here or by using the"contact us" link at the bottom of the page.

Nose Cone Help

J

jmwaterski

Member
I have a 1992 Checkmate Persuader 219. when we bought the boat it had a nose cone on it and would run around 65, last season after the first engine overhaul we saw 75 on GPS and still had the nose cone. Over the winter we have done more engine work to increase power. We have also had the outdrive serviced, painted and during this time it was noticed that the nose cone was loose so it was removed to clean everything up before putting it back on.

What we are trying to decide is do we need to put it back on. Is it giving us positive results now that we should be over the 75 mph mark maybe 80?

Any advice is appreciated!
 
I hear around 80 they start to help, I'd say leave it off and put it on later if you need it. I'd be on the lookout for a sportmaster or imco shorty, those would probably make more difference than the cone. Even if you just find a bare case you can always swap your parts in them
 
I saw a 4 mph loss when adding one. But then I was able to gain it all back and then some when I jacked it up to the surface. (outboard)

I think when running them deep they are less efficient. Mercury dropped millions of dollars into R&D to build their lower units. If they didn't design them with a cone shape, I have to believe they did it for a reason.

I second the idea of running without. If you get any blowout then you can add it. Every boat reacts different to changes. :thumb:

Good luck.
 
wired said:
I dont know how useful they are on an outdrive as you cant surface them.
Click to expand...

What's that mean, my outdrives surface. But even if they don't the shape and added length of the cones help reduce drag and not force the water as far away from the center of the bullet reducing prop slip.
 
jazzy said:
What's that mean, my outdrives surface. But even if they don't the shape and added length of the cones help reduce drag and not force the water as far away from the center of the bullet reducing prop slip.
Click to expand...


How far is the prop centerline over the pad on yours? Most all I/O's Ive seen were below the pad unless its a shortened outdrive.

I dont see any real gain in speed or prop efficiency until I get it 1/2" to 1" over the pad. Then I pick up several MPH . Even big eared Choppers get down in the 5-7 % slip range at those heights. Below the pad I'm lucky to get 15% on some of my props with out without the nosecone.
 
I'm 2" below the hull directly in front of the drives, but in a twin setup. I've never measured off the keel like you would in a single but I would guess at least six or eight inches above,drives are also on 12" boxes for setback. I'm seeing about 8% prop slip at wot. On the boat right now are coned drives with the water pickups filled in.
 
wired said:
How far is the prop centerline over the pad on yours? Most all I/O's Ive seen were below the pad unless its a shortened outdrive.

I dont see any real gain in speed or prop efficiency until I get it 1/2" to 1" over the pad. Then I pick up several MPH . Even big eared Choppers get down in the 5-7 % slip range at those heights. Below the pad I'm lucky to get 15% on some of my props with out without the nosecone.
Click to expand...

Horsepower to weight ratio has a lot to do with it as well.
 
Saw an article at bobs machine shop about lower units and the stock gearcase with bobs nose cone was faster than the cle gearcase and also heard if u not running in the 80's they just look cool that's about it!
 
jazzy said:
What's that mean, my outdrives surface. But even if they don't the shape and added length of the cones help reduce drag and not force the water as far away from the center of the bullet reducing prop slip.
Click to expand...


The added length of the cone actually increases drag which is one of the reasons they don't work very well below 80. With your prop shaft 2" below the hull and 12" of set back, you are still not running above the surface. Go back and watch Wildmans video from the transom of his 2100 at 95mph. That drive is surfacing!
 
I've read on S&F that it's not so much the mph as it is if it's surfaced or not and if you are using a lot of positive trim to get the boat aired out it will hurt your speed. A 15ft Hydrostream will get on the pad and allow you to surface the prop at a much lower speed than a Pulsare.

John
 
Articles, schmarticles. Those boat writers are worse hack hacks than gun writers. Its not the nosecone that makes you faster, its the pulling the lower out of the water that does it. Get it up high and utilize the low water pickup and forget you have a trim button . Thats when the nose cone turns a 75 MPH boat into a 85 MPH boat.
 
boatman4021 said:
The added length of the cone actually increases drag which is one of the reasons they don't work very well below 80. With your prop shaft 2" below the hull and 12" of set back, you are still not running above the surface. Go back and watch Wildmans video from the transom of his 2100 at 95mph. That drive is surfacing!
Click to expand...

Just to clarify on a twin setup you designate the prop centerline height at the point directly in front of the drives. So I'm 2"below directly in front of the drives. Since the hull is a v shape I'm several inches higher than the keel. Here's a pic, I've never seen another bravo boat rigged that high. I'm definetly not as high as wild man was getting with his hydraulic jack plate but I'm still surfacing the props. As far as cones go, my understanding of them is that yes at slower speeds the added drag mass of the cone causes drag, but as speed increases they lower it. It was explained to me like this: the lower has to make a hole through the water to move through it, so the longer the lower the smaller the diameter of disturbed water is at the props getting better bite.
https://picasaweb.google.com/m/view...key:Gv1sRgCO7-j7b9t7-r0QE/5987108007304969362
 
The longer cone doesnt make more drag through the water unless its trimmed up in which case it certainly does. If you are surfacing the prop the last thing you need to do is trim the motor up. Set it in plane with the hull bottom and call it a day.
 
You must log in or register to reply here.
Back
Top