Wheres Fobes? SPEED QUESTIONS TOO!!!
08-17-2003, 12:35 AM
#1
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Wheres Fobes? SPEED QUESTIONS TOO!!!
Hail Sutphen people,
Here's one to chew on...38' KV "Smith" Scarab with #4s spinning 30s with 557 800+hp motors one day does 89.2mph with six guys(some BIG) and 100gallons of fuel. Another day the owner changes the drive around to turn in and does 84mph with four guys and no fuel. Chime walks like a mother?/=$@*& when trimmed out to 5 on the dial with no rooster to see and just wont go faster. The water conditions weren't really too good(too smooth in spots) Boat spins 5600rpm...weighs almost 11,000lbs, and this boat did 100mph with 8lbs of boost, chillers and big wheels at 5900 rpm...with the drives normal...is this normal?
Here's one to chew on...38' KV "Smith" Scarab with #4s spinning 30s with 557 800+hp motors one day does 89.2mph with six guys(some BIG) and 100gallons of fuel. Another day the owner changes the drive around to turn in and does 84mph with four guys and no fuel. Chime walks like a mother?/=$@*& when trimmed out to 5 on the dial with no rooster to see and just wont go faster. The water conditions weren't really too good(too smooth in spots) Boat spins 5600rpm...weighs almost 11,000lbs, and this boat did 100mph with 8lbs of boost, chillers and big wheels at 5900 rpm...with the drives normal...is this normal?
08-17-2003, 07:37 AM
#2
Charter Member #40
Charter Member
I can respond based on what my 39 does with 4's on boxes, prop c/l 1.00" above bottom. When turning the props in, I have better speed as the transom is getting a little more lift, and since Sutphens normally have no problem with bow lift it seems to reduce the wetted surface. Turning in gives me a 100-200 or so more rpm. Rooster rail is lower than spinning out. Does not like docking and tough on backing up. Turning out is a little slower, maybe 3-4 mph. Great around docks. No problems on handling either way in the lower 90's speed wise.
My guess is that the Scarab does not have the bow lift characteristics compatible with getting more transom lift? Which would suggest the boat would also begin to bow steer with drives in? I am also assuming the drives are surfaced.
My guess is that the Scarab does not have the bow lift characteristics compatible with getting more transom lift? Which would suggest the boat would also begin to bow steer with drives in? I am also assuming the drives are surfaced.
08-18-2003, 06:57 PM
#3
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Bill
The boat had about six feet of water breakfrom the stern, if that. It chimed walked really bad over any kind of water we didn't take straight on, and if I trimmed it out to about six, we got 4mph more. Docking was terrible too. I liked the other way much better and it was much faster too. Theres no way in hell I'm going that way with my drives...6000lbs less weight and eight feet shorter at that speed and higher I'm going to want every bit of control I can get.
The boat had about six feet of water breakfrom the stern, if that. It chimed walked really bad over any kind of water we didn't take straight on, and if I trimmed it out to about six, we got 4mph more. Docking was terrible too. I liked the other way much better and it was much faster too. Theres no way in hell I'm going that way with my drives...6000lbs less weight and eight feet shorter at that speed and higher I'm going to want every bit of control I can get.
08-20-2003, 08:13 AM
#4
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Suphen30 and I had a conversation about this yesterday. The X dimension and setback if you have extention boxes play a big part in which way you should spin your drives. Of course prop selection (pointed or rounded ear) will also play a role. The only thing you can do is to try it because every boat is different.
