Reply With QuoteWhat gears are you running sounds like they are very low and the prop is suspect also.
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?
What gears are you running sounds like they are very low and the prop is suspect also.
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.
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.
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).]
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.
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LeE ss13
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.
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
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.
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?
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