height of stern drive on transom

Discussion in 'Boat Design' started by whitepointer23, Sep 28, 2011.

  1. whitepointer23

    whitepointer23 Previous Member

    i am about to cut out the hole for my volvo leg and am still not sure where the cav plate should be. i have been told level with bottom or slightly above. i always thought it was an inch below the bottom. if anyone can supply some info it would be appreciated. thanks.
     
  2. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 489, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Log onto the Volvo site and download the installation PDF, which will show you the appropriate heights for your specific drive.
     
  3. whitepointer23

    whitepointer23 Previous Member

    thanks par.
     
  4. Willallison
    Joined: Oct 2001
    Posts: 3,590
    Likes: 130, Points: 0, Legacy Rep: 2369
    Location: Australia

    Willallison Senior Member

    I'm rather surprised that it didn't come with all that info in the box.... or didn't you buy it new?
     
  5. whitepointer23

    whitepointer23 Previous Member

    its an old leg will. i rang a bloke that has one of my old boats this morning and he got the measurement off his leg which has the cav plate level with the bottom as i was told by imp-ish. so i cut the hole to suit. i tried to find the diagram on the volvo site par but i must be looking in the wrong place.
     
  6. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 489, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    They sometimes make this information difficult to find, but it's commonly available stuff. Glad you've got it sorted out. Is this the boat you're beefing up the transom on?
     
  7. tunnels

    tunnels Previous Member

    Like a out board cav plate level with or 10mm above depending on how far aft it is .draw it full size on a piece of plywood!!, its the underside of the cav plate you should be looking at . !:D
     
  8. whitepointer23

    whitepointer23 Previous Member

    yes it is par.
     
  9. whitepointer23

    whitepointer23 Previous Member

    thanks tunnels.
     
  10. u4ea32
    Joined: Nov 2005
    Posts: 416
    Likes: 14, Points: 0, Legacy Rep: 192
    Location: Los Angeles

    u4ea32 Senior Member

    Depends on how fast you want to go. The faster you go, the higher it should be. The higher it is, the faster you go. Reggie Fountain, who is one of the few experimental scientific boat designers (he measures every boat, and continuously varies factors) has been moving drives higher and higher for years. His latest boats have the drive shaft 2" above the bottom, so the cav plate is way up there. He has added roughly 50% top speed to his designs for same power over past 20 years. Hard to find another designer who has evolved similar improvements. There really is something to this scientific theory thing after all!
     
  11. Willallison
    Joined: Oct 2001
    Posts: 3,590
    Likes: 130, Points: 0, Legacy Rep: 2369
    Location: Australia

    Willallison Senior Member

    True - but the opposite is also true... if you want to go slowly, then the drive s better off at the lower end of the manufacturer's recomendations
     
  12. tunnels

    tunnels Previous Member

    I think this is a normal practical application so after all the sillyness of raising the unit 2 inchs for top speed we dont normally fish at 40mph so set to a useable level for most all situations usually for every 1 foot back the cav plate it can be raised 5 mm ==2 feet back 10 mm ! this is parctical and sensable . sure top speed is something we all like at times but for the gain of a couple of extra mph its not nessasary and chances of cavitation in a tight turn , :eek:
     
  13. IMP-ish
    Joined: Jan 2011
    Posts: 389
    Likes: 9, Points: 18, Legacy Rep: 150
    Location: united states of america

    IMP-ish powerboater

    To raise the x-dimension 2" Fountain has a transom notch - are the drives also set back on setoff boxes?
     
  14. whitepointer23

    whitepointer23 Previous Member

    my boat only does 25 knts and i will be using it at 10 to 15 knts . i fitted the leg with the cav plate level with the bottom. looks right to me. thanks for the replys.
     

  15. u4ea32
    Joined: Nov 2005
    Posts: 416
    Likes: 14, Points: 0, Legacy Rep: 192
    Location: Los Angeles

    u4ea32 Senior Member

    Sounds like you did the right thing for those speeds.
     
Loading...
Forum posts represent the experience, opinion, and view of individual users. Boat Design Net does not necessarily endorse nor share the view of each individual post.
When making potentially dangerous or financial decisions, always employ and consult appropriate professionals. Your circumstances or experience may be different.