Modifying Transom on Trophy 2106

Discussion in 'Boat Design' started by kapukavik, Jun 6, 2013.

  1. kapukavik
    Joined: Jun 2013
    Posts: 4
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Alaska

    kapukavik New Member

    Modifying Transome

    I'm looking at the possibility of modifying the transom of my Trophy 2106 to accommodate a Honda 135 with a 20" lower unit. Right now it is set up as a 25", and I just want to cut it down without having to go through all the hassle of extending the lower unit (at a quoted cost of $2500). I was thinking to just cut it down, and glass over the cut and mount the motor...should be a simple fix. Any thoughts?
     
  2. kapukavik
    Joined: Jun 2013
    Posts: 4
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Alaska

    kapukavik New Member

    I'm looking at the possibility of modifying the transom of my Trophy 2106 to accommodate a Honda 135 with a 20" lower unit. Right now it is set up as a 25". I was thinking to just cut it down, and glass over the cut and mount the motor...should be a simple fix. Of the three solutions I've looked at: 1)extend the lower unit $2500, 2)buy a bracket $1200 but comes with moving a lot of weight back or 3) cut down the transom $200...that one seems the best. Of course it means losing that 5" of height, which might be a problem in rough water (I boat in Valdez Alaska).

    Anyone have any thoughts or experience on this?
     
    Last edited by a moderator: Jun 7, 2013
  3. rasorinc
    Joined: Nov 2007
    Posts: 1,854
    Likes: 70, Points: 48, Legacy Rep: 896
    Location: OREGON

    rasorinc Senior Member

    Do you need to add an extra layer of plywood to handle the HP.? going to 20" should not present a problem as you need to install an upward tilted splash plate in front of the engine out of 1/2" ply the size of the transom opening with vertical side pieces and 2 holes for draining through the transom below the engine. About a 30* rise+ will be enough to drain wave lap over the transom.
     
    1 person likes this.
  4. PAR
    Joined: Nov 2003
    Posts: 19,133
    Likes: 473, Points: 93, Legacy Rep: 3967
    Location: Eustis, FL

    PAR Yacht Designer/Builder

    Whenever possible the longer shaft setup is better, if only to protect the boat. I'm not sure of the 2106's transom core, but it should be at least 2", preferably thicker for the 135. The other considerations, as Stan has eluded to are the splash well, which might need modification. I find it hard to believe that Trophy would have a well molded into their deck cap, that is too tall for a 20, though anything is possible. Measure carefully and insure a good laminate schedule, to insure the cap and hull shell have their strength and stiffness restored after the modifications.
     
  5. kapukavik
    Joined: Jun 2013
    Posts: 4
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Alaska

    kapukavik New Member

    The boat had a Evinrude 175hp on it, so horse power should not be a problem...the BF135 is a LOT heavier...nearly 500lbs, compared to the 300lbs for the Evinrude, but it should not be torqier...(is that a word?). The transom width is 2", and I don't know what the core is..it is already set up for an outboard, just 5" too high. The splash well will not have to change, I don't think...it looks like there will be enough room when the engine is tilted up.
     
  6. Mr Efficiency
    Joined: Oct 2010
    Posts: 8,162
    Likes: 395, Points: 83, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

    There should be a diagram available from Honda that shows the clearances required when the motor is fully tilted. You don't want to proceed till you know it will fit in there.
     
  7. CDK
    Joined: Aug 2007
    Posts: 3,324
    Likes: 145, Points: 63, Legacy Rep: 1819
    Location: Adriatic sea

    CDK retired engineer

    Sounds easy and straightforward. Usually something unexpected turns up, like the well not being deep enough to tilt the engine or the transom needing reinforcement. Make sure the cutout is wide enough for the engine to fully swivel both left and right.

    Have you considered mounting a bracket?
     
  8. Mr Efficiency
    Joined: Oct 2010
    Posts: 8,162
    Likes: 395, Points: 83, Legacy Rep: 702
    Location: Australia

    Mr Efficiency Senior Member

  9. Boat Design Net Moderator
    Joined: Feb 2010
    Posts: 500
    Likes: 95, Points: 28, Legacy Rep: 1004
    Location: www.boatdesign.net

    Boat Design Net Moderator Moderator

    <duplicate thread merged to keep the discussion together>
     
  10. kapukavik
    Joined: Jun 2013
    Posts: 4
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Alaska

    kapukavik New Member

    Really good advice...I'm on it. Thanks! I was going to do an experiment on a stand, which I will still do, but this is a better first step.
     
  11. keysdisease
    Joined: Mar 2006
    Posts: 794
    Likes: 43, Points: 28, Legacy Rep: 324
    Location: South Florida USA

    keysdisease Senior Member

    Take a look here:

    http://www.thmarine.com/products/Outboard-Jack-Plates?gclid=CNjwhNS30rcCFUtk7Aod5h0A6A

    Manual jack plates or set back plates, should make the modification a bolt on without changing the transom plus any performance gained by set back.

    http://www.thmarine.com/products/Ou...atic-Height-Plates/Hi-Jacker-Fixed-Jack-Plate

    This tough 3/8" thick aluminum bracket provides an inexpensive solution to mounting a long shaft outboard to a short transom. Also great as a fixed jack plate for all V6 outboards. Handles all outboards up to 150 hp. Three engine mounting holes and two transom mounting holes combined with a 3" designed lift allows a total of 5 1/2" of lift with a full four (4) inches of setback.

    Just turn it upside down.

    Steve
     

  12. liki
    Joined: Nov 2008
    Posts: 220
    Likes: 12, Points: 18, Legacy Rep: 114
    Location: Finland

    liki Senior Member

    Mounted the normal way the outboard will raise higher than the transom edge. The other way you will likely have clearance issues with the outboard and transom.
     
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.