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Thread: gear ratio ???

  1. #1
    mike37
    OK you gear heads what takes more Horse Power
    Set up 1
    26p prop 1.36 gear ratio 5000 rpm 83mph
    wouldnÂ’t this set up be better
    Set up 2
    28p prop 1.50 gear ratio 5000 rpm = 81mph

  2. #2
    Dennis Moore
    I don't know if anyone can answer that question but from my years of working at Hallett boats I never saw anyone really happier with 1.32:1 gears after we made the switch. Some boaters didn't like it. We could never figure out which boats needed it (the exception was really high horsepower boats but they would blow Bravo drives every weekend so who knew?)I am not much help here but if the boat will handle a higher pitch prop without being tossed around by the aggresive pitch I would think that the 1.50:1 would be my choice.
    Dennis Moore
    Merc Master Tech

  3. #3
    spectras only
    Dennis, I have one of Bud's dinosaur [72 spectraV-drive]which I love for the way it handles big water.The only problem is too much wetted surface.It's extremely quick to plane with a 14X13 cupped three blade prop [OJ].Unless it's a foot of chop out there ,it won't run faster than 53MPH in smooth water.It still has the original LS-6 ,rec heads ,hydraulic cam , 500 lift in/exh,TR2 manifold and a 800 Holley DP .Don't know the duration spec on the cam .I guess around 220/230 @ 0.50. At what RPM does this engine makes the max HP with this cam? I run 4% underdrive with the ACe Champ drive.I can flip this drive 180 deg to achieve 4% overdrive.Should I try a 13X15 or 13X16 prop to get a little more top speed.I'm not concerned about holeshot.Thanks

  4. #4
    Senior Member
    Join Date
    Feb 2009
    Posts
    763
    Why wouldn't you try and run the higher gear ratio with the lower pitch prop or vise versa? Just wondering.

  5. #5
    spectras only
    Stix, thanks for the advice .I was going to flip th drive for the higher ratio,but I'm still boating as the weather holds out here.I can try different props from the shop ,which is quicker wink than removing my floor to flip the drive. The LS-6 engines were solid tappet equipped for the Chevelles ,so my guess is they could handle higher RPM's than the hydraulics in the marine version .There are quite few 24 spectras out there [most of them I/O],and I've wondered if someone experimented with different props beside gear ratios with their V-drive .

  6. #6
    Senior Member
    Join Date
    Feb 2009
    Posts
    763
    I wasn't sure if there was a reason that they made changes like that or what. We have a different application but we still run a v-drive. We are always trying new props. I bet our last full season we tried at least 6 or 7 different props and maybe changed our gear ratio two or three times. Our big thing was we tried to change one thing at a time that way you know what things did what. I'm not saying to go out and buy a bunch of props but maybe borrow or try a couple at a gear ratio that you are currently at to see if it does make a difference. Let me know what your results were if any?
    [ September 25, 2002, 05:21 PM: Message edited by: Stix818 ]

  7. #7
    mike37
    I don't know if anyone can answer that question but from my years of working at Hallett boats I never saw anyone really happier with 1.32:1 gears after we made the switch. Some boaters didn't like it. We could never figure out which boats needed it (the exception was really high horsepower boats but they would blow Bravo drives every weekend so who knew?)I am not much help here but if the boat will handle a higher pitch prop without being tossed around by the aggresive pitch I would think that the 1.50:1 would be my choice.
    Dennis Moore
    Merc Master Tech are the 1.32:1 weeker than the 1.50:1

  8. #8
    Dennis Moore
    Spectras only,
    I see Bud all the time, he is retired and living in Boulder, Nevada. I will tell him about this chat on the Forum.
    Dennis

  9. #9
    Dennis Moore
    Spectras only
    If it is an original LS6 it has a solid lifter camshaft. Less than .500 lift, 114 LSA and a very slow opening and closing rate. An old design camshaft from the 1960's. Big performance increase from a modern hydraulic cam!
    Dennis

  10. #10
    Ric 232
    Mike,
    If the numbers you posted are real, then you already know which is better. If they are calculated hypothetical numbers only, the rule of thumb is to stay with your current gear until you run out of prop options. The higher the pitch, the more efficient the prop runs.
    Ric
    [ September 25, 2002, 08:15 PM: Message edited by: Ric 232 ]

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