Nose cone, good or bad idea.
 

I have heard that they can slow ya down in some app's, under a certain mph but help if running better then a certain mph, I am running in the 70's with this boat now, was just wonder if at this point a cone would benifit me.


Thanks John :boat:

Most likely a nose cone wont do anything for you unless your running over 80 mph and or experiancing blow out or loosing bite on the water at reasonable trim levels.

70's No
80's Maybe
90's Yes
:drink:

Wait till you add that supercharger. I seriously looked at a Hydromotive nose cone, prior to my Imcos. I was told just what zt260 said. I also think there is an art to properly getting the nose cone attached and blended. I have seen some that didn't turn out.

Ok. I am losing bite it seems when bringing the drive up, the boat keeps pulling, then loses bite, so I think I might take a gamble and try it next spring.. Thanks for the info..
John

At less than 80mph a drive spacer would be a simpler approach. Many people lose speed and see the drive dart or chine walk. Not to mention spacers can be easily added and removed. Nose cones can’t. If you’re set on trying it, I would look to borrow an imco lower from someone rather than alter yours. Good Luck

I would look at your slip numbers at WOT to determine the need for nose cones/spacers. My situation was 80 mph 11% slip. Went from 500 hps to 600 hp motors, speed went to 86 mph at 16% slip. Boat was very insensitive to trim and also different props did not make a difference i.e. labbed vs. non-labbed. Tried 1" drive spacers that did not help slip. Put on nose cones (pointy kind) from Teague, slip went to 9.5% at 91 mph.

See the Thunderstruck goes 90 mph in the Active Thunder section for more info.

Talk to Throttleup and the parts guys at Teague Marine. They were very helpful.

Tom

Quick question.

How do I determine the slippage on the props?

I just ran a set of hydros and it's slower then my Bravos. Bravos are 24" P Hydros were 25" P and the speed with the hydros were actually lower. Harder to get up on plnane as well, so I think it's a higher slipage.
How do I test this??

Thx

p

How would I go about finding the slip numbers, Julie at throttle up is prolly tired of me asking questions about this thing. This seems to be the right prop 30p bravo, is the one that was recomended to me from them, It doesn't feel like it is slipping very much compared to the other ones i have tried, from what she came up with my mph should be 80ish with about 16% slip in this thing. It isn't quite there but 75gps.I might have to try a labbed 32p. Also I am running a alpha1 drive, do they even make spacers for them? There is more left in this thing just need to fine tune. Chine walking all day. What do I do to eliminate slip? Thanks for any and all input guys..

John

You can use this page to calculate your slip, use a GPS to get the actual speed and a tachometer that you know for sure gives the correct reading. http://www.go-fast.com/Prop_Slip_Calculator.htm Hope this helps.

A propellor's pitch determines the theoretical distance the boat would move after the prop turns 1 revolution. Throttleup recommends using 1" less pitch than advertised for BI props. So, for a 30" B1 prop the boat should move 29" per revolution. But, the props are not 100% efficient, so the prop "slips" somewhat.

The formula is:
Slip = (1-actual speed/theoretical speed) x 100%

Theoretical Speed = rpm x pitch/1056/gear ratio

For example:

You are turning 30P BI's at 6000 rpm with 1.5/1 Bravo I outdrives and your GPS/Radar speed is 92 mph:

Theo. Speed = 6000 X 29 /1056/1.5 = 109.9 mph

Slip = (1-92/109.9) X 100% = 16.3%

Theoretical speed is the speed that the boat would go if there were no slip. Comparing actual speed to theoretical speed on a 100% basis yields the % slip.

Once you see how the number work use the go-fast web site calculator. It's much faster.

Slip is usually only applicable at WOT. You need to be honest with yourself and take the rpm and a reliable speed to calculate your slip. People that lie to themselves take away the tools that would enable them to start picking away at a slip/inefficiency issue.

Also, I believe that part of the efficiency process should include an evaluation of the hull straightness. My plan is to have my hull looked at this winter.

Tom

First thing to understand is slip is not bad. Actually you need some or the drive would break all the time. You can run anywhere from 5-25% slip and be setup perfect. As long as the boat handles well, goes fast, and runs economically your good. Don’t get hung up on slip. It's just a gauge.

BTW, No prop is all around perfect. They are all a compromise.

Thanks a lot TOM. Big help there. Only differnece is I am running a alpha 1 with 1.98 gears.. I will try to figure this out tommorow, it is getting late now. To be honest the hull on this boat has lil to no hook in it, surprised me. I cruise the boat at about 34-3800 with a cruise of about 40-45ish., maybe a bit better, but not really concerned on cruisen, but the top end, it cruises good.
All in all I am satisfied with the speed but just would like to have it all fine tuned, to get the most out of it. Would love to have a honest 80 mph 202 stinger with stock power..:party-smiley-048:
John

I've been researching this for a few days and a few good sources have pointed out many alpha's start having issues high 60's and that nosecone is needed. My resdearch is only on smaller single engine boats with alpha's. Hydromotive nosecone's where recommended.

Again, this is what I found (not experienced) and just letting you know. Search here, Hotboat, and SW under 'alpha nose cones.'

So can anybody else verify this, is it true about the alpha, a cone, again this is a small boat with a single.
Thanks John

Also what I came up with on the slip calc, doesn't seem right, can this be right.
GEAR 1.98-1
PITCH 30p but entered 29p
RPM 5300 = a theo speed of 74. Gps is at 74 and some change so it is giving me 0% slip using 29p and 3% using a 30p, can that be right?? Duno is that possible to have 0 slip, I think not.
I will have to go run the boat again and note them to see for sure.

John

Anything lower than around 10% for a V-hull means one of your numbers is off. Test one more time and be very certain of the numbers.

Will do and I am sure 0% isn't freaking possible. So hopefully I will get some good numbers this weekend, hope the the tach is bsin me(gaffrig) and the gps is legit(garmin). I will try on flat water, even though it will run better in a cop, but see what happens.
again thanks
JOHN

You may also want to double check your gear ratio. I know when I bought my boat i was told it had a different ratio than it turned out to be. I was told it had a 1.35 ratio or something like that and that it had been GPS'd between 80-85. This all sounded good being as I was turning it 5400 rpms with a SS 24 pitch 3 blade. However it turned out to be false, it has a 1.50 ratio and only GPS'd 72 with that prop. Also, mine has the old Alpha SS, which is basically an older Alpha with a lower that was made with the elongated pointed case. I actually had a prop guy tell me how big a mistake i made putting a nose cone on that drive. Even after I explained it was original Merc he said I was wrong and that someone had added it. At that point I gave up trying to talk to him.

Are you sure of the 1.98 ratio in the Alpha? That ratio was used with 4 cylinders. Powerboat did a test years back and found the Alpha Gen 1 would experience hydrodynamic blowout around 70mph. I figure there are some factors that could affect the speed but it's around there that they are required to go faster with the Alpha drive. The Bravo has no problem at those speeds as it has a better aspect ratio.

I have Hydromotive nosecones on my Alpha Gen 1's. They require alot of blending, sanding and elbow grease to mount and make look like factory. I have the process down to a science. I'm running a 355ci SBC with around 400hp and am seeing 70-73 gps most of the time.

Give us some specs on your stinger's engine? Seems to be running good.

http://img504.imageshack.us/img504/8...yingsk9.th.jpg

http://img250.imageshack.us/img250/1...ted2lx7.th.jpg

My research was made because I was tuning an Alpha equipped boat this past Sunday that seems to be experiencing major prop blow out (feels like coupler disconnects) at 66mph (GPS) and just over 5100rpm engine rpm. You can feel it start to do strange things just before 5100rpm. 1.47 ratio '90 older style alpha. We repeated this almost a dozen times in same 2hrs in same water.

Will try other props to see if it helps go past this but will be getting a nose cone anyway.

Ryan00TJ - your name came up in a lot of my searches. Thanks for sharing your info.

I beleive I am exp'n the blowout. This boat came with a 4.3 175hp v-6 and I am sure the gears are 1.98's. If The cone will truly help this on the alpha I don't mind doing the work for the cone.
RYAN I just purchased the engine a month or so ago, when we sold the 6 banger. It is a 96 or 97 fuel injected 350, other then a computer tune from ASM it is stock. I have put a set of emi exhauste on it. I have read that the stock tune is pretty good on those engines, the tune usually just ups the rev limit. There might be something more then just that in this tune it is defenatly making more power then we thought, I could spin a 28B 4 blade to the box 5500rpm, no problem, can also hit it with this new 30p B1, so we are thinking the hp might be around 365-370, could be wrong but none the less this thing screems, am right about the 75mark on gps. I just want to go faster, every lil bit counts know what I mean. I will have to research more on the cones and alphas, but keep the info and exps coming.
John