Luhrs 28 with single 454 V-drive

Discussion in 'Inboards' started by 7228sedan, Nov 13, 2009.

  1. 7228sedan
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    7228sedan Senior Member

    I recently took ownership of a 1972 28' Luhrs sedan bridge. The boat was repowered a while back with a Mercruiser 454 coupled to a Velvetdrive 72 V drive. It has the 1.5:1 ratio in it. I have not run the boat yet as the transmission needs a rebuild due to bad bearings in the V drive. I am concerned that the ratio is not correct for this size boat. Does anyone have any experience with a similar combination?
     
  2. gonzo
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    gonzo Senior Member

    The ratio looks OK. What diameter prop do you have?
     
  3. 7228sedan
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    7228sedan Senior Member

    I have'nt checked out the prop yet. The boat is being hauled to my yard on 11/17. I have alot of experience with sterndrive boats, this is my 1st inboard. What size would you expect to be on there?
     
  4. gonzo
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    gonzo Senior Member

    On a sterndrive with that engine and a 1.5 ratio the diameter would be about 15". It should be similar.
     
  5. 7228sedan
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    7228sedan Senior Member

    I'm going to take a ride to the yard where she's on blocks to take a look this weekend. I assume that the pitch & diameter should be marked into the prop?
     
  6. gonzo
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    gonzo Senior Member

    It is usually stamped on the face of the prop. Diameter is easy to measure with a tape from the center to the tip of the blade.
     
  7. 7228sedan
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    7228sedan Senior Member

    I'll check it out this weekend & get back to you. Thanks for the information!
     
  8. mongo75
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    mongo75 Senior Member

    On my 440 powered 25' Luhrs, the prop guy told me I would need a 16x16 cupped prop. I too am new to inboard formerly being an I/O guy, and for the engine size I thought the prop is a bit small, but it's a good starting point I guess. Your best bet would be to find a prop shop that'll let you test different props, but it's a pain in the *** when you're not on a trailer, having to dive every time you want to change props.
     
  9. 7228sedan
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    7228sedan Senior Member

    I finaly got around to cleaning up the prop this weekend; it is a Michigan Wheel 17 RH 16. I assume that it is a 17 diam. 16 pitch. Any comments?
     
  10. baeckmo
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    baeckmo Hydrodynamics

    Stick to that prop. Provided the engine is ok, this is what is needed!
     
  11. 7228sedan
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    7228sedan Senior Member

    I finaly got around to pulling the bad trans & V drive out. Come to find out, it is a 71 series Velvet Drive, not a 72 as I was told. I have a fresh 72 series ready to drop in but I have 2 concerns.
    1. the 72 series bolted to the V Drive puts the output shaft coupling about an inch further forward (away) from the propeler shaft. Will I need a spacer for this, or is there a way for me to push the whole shaft inwards to take up the extra space?
    2. What is the best way to beef up the mounting beds for the transmission? I saw a post by mongo75 where he had a similar problem. When I removed the transmission, the port trans mount pulled right out of the wood that is through bolted to the stringer. Can I cut out the rotted wood & replace with new? If so what species of wood dould be recommended?

    Thanks all
     
  12. TollyWally
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    TollyWally Senior Member

    I can't help but wonder if a rotted mounting member had anything to do with the bearings going bad in the first place. You may need to do a little bit more than splice in a bit of new.
     
  13. Jango
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    Jango Senior Enthusiast

    Since the 72C Trans is about an inch longer than the 71C, in addition to repairing the wood problem, you will need to RAISE the motor/ trans slightly to properly align with the drive shaft - probably less than a 1/4 inch depending on shaft angle.

    Shaft length problem can be taken care of by moving engine/trans Aft, about an inch,OR installing a longer shaft or if you're lucky and have more than inch clearance between prop and strut, just pull the shaft/prop forward to match couplings.
     
  14. gonzo
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    gonzo Senior Member

    You may need to cut the shaft if the distance from the face of the prop to the cutlass is too long or if it touches the rudder. Otherwise, it will line up the same. The 72 is a bit over an inch longer.
     

  15. 7228sedan
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    7228sedan Senior Member

    I have not yet installed the new transmission, however the shaft does slide in & out of the hull fairly easy. It will easilly make up the difference in transmission length; my question now is, should the shaft slide in & out of the hull? It's not like it goes with gravity, but I was able to push on the prop with my hands & slide it forward.
     
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