PDA

View Full Version : V-Drive help



hcb26
12-27-2001, 06:29 PM
I just got done putting a blower on my 21ft. Howard v-drive,the motor is a 468 cu.in.the blower is just a 174,the motor should have around 450 to 500hp. My question is when I recently took it out to test drive it, I ran 69 mph, hitting the rev. limiter at 5900 rpm, im turning a 13,14 prop, should I regear it or get a bigger prop or just have the prop I have reworked?

pgf127rt
12-28-2001, 04:54 AM
What gears are you running sounds like they are very low and the prop is suspect also.

hcb26
12-28-2001, 07:26 AM
I dont know what gears are in it, thats part of my problem, before I put the blower on everything was about right I was turning the same prop 5000 rpm at 60mph, so I know I need to do something I just dont know whats the easiest and cheapest way to go.

superdave013
12-28-2001, 08:14 AM
What v-drive do you have? Is it a Casale C-500 or a Casale Quick Change?
I would start with gears but the one for C-500s are $$$ new and hard to find used.
At least find out what ratio gears you have. I bet they are in the 15% range.

Stab-n-Steer
12-28-2001, 10:46 AM
hcb26,
Using the 'ol speed caculator formula with a 13% slipage it works out that you have only a 2% overdrive, which I think is unlikely. Maybe a higher slipage number should be used for your boat since it is 21'. The 13% is usually within 2mph for my boat (only 16 1/2') when checked with a GPS. I have a little Excel speadsheet I made with the formula if anyone wants it. You just plug in the variables and it gives you a theoretical speed. Also, you can create your own with the formula below. The easiest way to check your gear ratio is put marks on the input and output shafts that line up. Rotate the driveline until the lines line up perfectly again. Then divide the propshaft rotation by the driveline rotation. Example,
Propshaft 14, Driveline 12, 12/14=1.167 or about 17% overdrive.
Speed=(((1-slipage%)xpitch)x(gearratioxRPM)x60)/63360
Randy
[This message has been edited by Stab-n-Steer (edited December 28, 2001).]

LeE ss13
12-28-2001, 11:44 AM
I have found that 21' cruisers run about 22 to 25% slipage under 100mph. I would say the V-Drive has 9% to 12% gears. I suggest trying the easiest thing first. Try a big eared 2-blade 11 1/2" x 15 prop. If you are going to limit the rpm to 5900, eventually a bigger gear would be needed.
---------
LeE ss13

Infomaniac
12-28-2001, 03:26 PM
hcb26 Take the rev limiter off. That is the cheapest. It may only be limiting it a few hundred RPM. If it were me I would give it a try. A very careful try.

Stab-n-Steer
12-28-2001, 03:47 PM
ss13,
Your numbers make more sense. At 22% slipage, 69 mph and 5900 rpm, it works out to be 13% gears in the box...
S&S

VD CRUISER
12-29-2001, 02:30 PM
HCB26,
22% slippage is what I have in my 21' Howard at over 100 mph with a 12x16 2 blade. Did you ever figure out what type v-drive you have, split case or C500, also what type prop are you using, 2 or 3 blade, bronze, steel or stainless. My boat handles better and runs better with more overdrive and a smaller diameter prop like 11 1/2 or 12 dia.

hcb26
12-29-2001, 05:50 PM
vd cruiser I have a c500 and the prop is a 3 blade bronze,From what I have gathered I think I am going to try a slightly bigger prop,its a menkins 12x15 3 blade stainless, hopefully that will do the trick,what year is your Howard, do you ever take it to Havasu?

VD CRUISER
12-29-2001, 07:19 PM
hcb26,
My Howard is a 1983,bought it new from Howard Brown himself. Made a lot of changes to it over the years. I also have a Menkins 3 blade stainless, 11 1/4x15,lot smoother than the 2 blades. What year is your boat? I'm on the east coast,(VA.) haven't made it to Havasu yet. I really wanted to come to the V-DRIVE regatta but its a long tow.

hcb26
12-29-2001, 10:38 PM
My 21 is a 1987, that I just picked up last april, I striped it down to a bare hull and went to work, I got it running by July 4 weekened, it was diffently a project, I also have a 2000 26Ft Howard Cat which is my real Hotrod so that takes a lot of my time up. I have owned 3 Howards and cant say enough about them. The V-drive regatta is a lot of fun, you should try to make it this year, but that is a long tow from the east coast.

Stab-n-Steer
12-30-2001, 08:07 AM
hcb26,
When is the V-Drive Regatta this year?
S&S

hcb26
12-30-2001, 08:34 AM
stab n steer, Im not sure of the exact date, they usually announce it at the LA boat show which is in early March this year.

superdave013
12-30-2001, 10:34 AM
Originally posted by hcb26:
I just got done putting a blower on my 21ft. Howard v-drive,the motor is a 468 cu.in.the blower is just a 174,the motor should have around 450 to 500hp. My question is when I recently took it out to test drive it, I ran 69 mph, hitting the rev. limiter at 5900 rpm, im turning a 13,14 prop, should I regear it or get a bigger prop or just have the prop I have reworked?
hcb26, Is your Howard the boat that Hot Boat did a write up on? I was at the last HB v-drive regatta too. Can't wait until the next one.

hcb26
12-30-2001, 11:42 AM
superdave, No ***boat didnt do a writeup on mine,I belive the one your talking about is a blue 21ft Howard. Do you own a Howard?

superdave013
12-30-2001, 01:34 PM
Originally posted by hcb26:
superdave, No ***boat didnt do a writeup on mine,I belive the one your talking about is a blue 21ft Howard. Do you own a Howard?
Nope, I have a 20' schiada.

V-Kid
01-08-2002, 08:53 PM
S&S
Thanks for that info on figuring out the % also the formula for gear,rpm,prop,speed can it be used in different orders to figure out each spec. What the hell is slipage? And what would my 16 ft rayson be.Could you please do the calculations for me using 7000 rpm and 100 mph . DO you think 460hp and 502 ft lbs can accomplish this
Kid