Need Help with Gap

Discussion in 'Fiberglass and Composite Boat Building' started by mhayessummit, Aug 10, 2010.

  1. mhayessummit
    Joined: Aug 2010
    Posts: 2
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Knoxville

    mhayessummit New Member

    I am a new boat owner so please forgive me if I state something wrong but here it goes.

    I have a bass boat and one of the upper mounting bolts for the outboard has pulled through the fiberglass on the inside of the boat. This is now fixed but now I have a 1/8" gap between the jack plate and the boat. I know that I need to seal this to prevent what happened last week(almost sank)

    What do I need to use to fill this gap? I have heard about 3m 5200 and 4200 but dont really know which way to go at this point.

    Thanks for any help you can provide. Pictures are below.
    Image is at link below

    Attached Files:

  2. ondarvr
    Joined: Dec 2005
    Posts: 2,846
    Likes: 502, Points: 113, Legacy Rep: 506
    Location: Monroe WA

    ondarvr Senior Member

    When the bolts pull trough like that it normally means the transom wood is rotten and needs to be replaced.

    The other issue is there should be no gap between the transom bracket and the hull, plus using a sealer around it will be of no value.
  3. mhayessummit
    Joined: Aug 2010
    Posts: 2
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Knoxville

    mhayessummit New Member

    The top has been repaired. The gap only exists because I have not tightened the bolts back up. I just need to know what to apply between the jack plate and the back of the boat to prevent water from entering the boat.
  4. tinhorn
    Joined: Jan 2008
    Posts: 575
    Likes: 20, Points: 18, Legacy Rep: 310
    Location: Massachusetts South Shore.

    tinhorn Senior Member

    Dude, I'm no powerboater, but shouldn't you replace that coathanger with a pin?

    A good fiberglass guy could replace the transom wood from the inside, so you wouldn't have to worry about repairing the metalflake gelcoat.
  5. ondarvr
    Joined: Dec 2005
    Posts: 2,846
    Likes: 502, Points: 113, Legacy Rep: 506
    Location: Monroe WA

    ondarvr Senior Member

    You don't have a jackplate, that is the transom bracket and no sealent is required there, you should use something like 3M 4200 in the bolt holes though.

    When a bolt pulls through it typically can't be fixed quickly or easily, the bolt pulling through means there are bigger issues.
    How was it fixed? I would hate to see you run into problems on the water.
  6. Landlubber
    Joined: Jun 2007
    Posts: 2,640
    Likes: 124, Points: 0, Legacy Rep: 1802
    Location: Brisbane

    Landlubber Senior Member

    ....when drilling to attach an outboard to a transom, the my procedure is to drill, from the inside out, a hole with a SpeedBore type drill, so that the drill bit just protrudes through the transom and out to the other side. The tip only comes through. This hole is drilled to, say 1", if you are using 3/8" bolts.

    The hole is then filled in with solid epoxy glue to make a nice solid plug. The inside is covered with tape to allow the epoxy to dry and not ooze out.

    Next day the correct size drill for the bolts is used to drill through the centre of this epoxy block with just slight clearence for the bolt, such as a 3/8" drill.

    The bolts are then inserted a few threads only and 3M or Sika is used from that point on to create a nice casket seal through the entire shaft. Do up using a tension wrench to the desired tension and clean up any excess sealant.

    This method will result in a sealed transom, and nice compression blocks for the outboard bracket to clamp up to.

    Very few installers do this, most just drill and seal the bolts, which results in rotten transoms and compressed timbers of the transom.

    As previously stated by another member, most likely your transom has been buggered and need replacing if the wood has crushed so easily.
  7. J3
    Joined: Jun 2010
    Posts: 60
    Likes: 1, Points: 0, Legacy Rep: 16
    Location: MI

    J3 Junior Member

    Don't use 5200 on anything you'll need to take off again or it will make a mess out of one side or the other or both!

    However, my mechanic uses 5200 as a quick and dirty way to cote holes he drills. It gets thinner after a while and has a tenacious adhesion. He lets it dry before inserting the bolt into the hole. Not nearly as good I think as Landlubber's proper method of overdrilling and using epoxy and then drilling again, but probably better than nothing to seal the holes.

    I've seen washers dent into fiberglass but if it pulled all the way through I'd look carefully at the wood quality as the others have said. Did water leak in through the bolt holes over time and rot it? Also did you have room to install a backing plate now if it's a light layup but sound?
  8. pescaloco
    Joined: Feb 2006
    Posts: 301
    Likes: 10, Points: 18, Legacy Rep: 81
    Location: so. california

    pescaloco Senior Member

    Like others have stated you may very well have soft or rotten wood in the transom that is compressing. Take a quarter or a screwdrive handle and tap the outside transom corners you will hear a very solid and sharp rap. Then work your way in, listening to the tone of the rap if it sounds like a dead thud then likely your transom is soft.

    To answer your question thought I think you need a back up plate or very large washers made of aluminum plate under your bolt heads on the inside of the transom (this is need to spread the load). Seal the bolt holes (landlubber meathod is the right way) with 4200 sealant. Tighten it all down and if a small gap remains on the outside it is a cosmetic issue that can be delt with by applying a bead of marine sealant or silicone.

    Lastly grab the leg (lower unit) when it's all torqued down and yank up and down (hard) while some watches the bolts from the inside and the gap on the outside. This will not even come close to the forces that are exerted on the transom when you trailer the boat but it should give you an idea if your solid.
  9. tunnels

    tunnels Previous Member

    You need a decent sized plate on the inside to give a bigger load bareing surface even a 1/4 thick bar to go across would be better . to carry all the load of the bolts
  10. Homefront
    Joined: Oct 2009
    Posts: 41
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: Eastern Pa

    Homefront Junior Member

    You will ultimately need a permanent fix, if you want to keep fishing (or whatever) in that boat some years from now.

    My friend and I recently repaired that same problem in his 20' Grady White and we did the repair like this:

    Remove the motor.

    Remove the aluminum cap from the top of the transom.

    Use a router or a Dremel or any appropriate too to remove the fiberglass from the top of the transom; ONLY from the horizontal section the motor sits on, edge to edge going across.

    Using a chainsaw, CAREFULLY dig down into the area beneath where you removed the fiberglass to cut up and remove the soft/rotten wood from between the inner and outer layers of the glass hull. DO NOT allow the chainsaw to "pop out" through the outside of the transom or the inside of the hull. If you're careful you'll hardly touch the boat glass as you go...take your time here.

    After removing the bad wood, or going as far down as your chainsaw can reach, you have to assess what you see... it's likely the remaining wood will be at least wet. You may have to move the boat to an enclosure or rig up tarps over the stern to keep rain out. Set up a fan and rig it to blow down into the excavated transom and let it go for as many days as it takes to make things reasonably dry down there. Use the sun to your advantage, too.

    When the above is complete, use a quality duct tape (like Gorilla Tape from Home Depot) to seal over any exterior AND interior penetrations in the transom, such as bolt holes, motor well drain holes, hardware holes, etc..

    Since you've removed the structural interior of the transom, the outer glass skin of the hull may no longer be flat, so apply a straight edge (like a straight piece of 2x4, on edge), and use a couple of big clamps on it to flatten the transom out again; this is very important. Failing to do this could result in a bulge where the motor mounts.

    Buy at least 1 gallon of a good epoxy with slow hardener; we used U.S. Composites. Mix up and pour enough epoxy into the excavation to fill it to roughly 1" at the bottom. This will be trial and error as to how much to use, but you want to see liquid epoxy down there. Now's the time to start checking for epoxy leaks inside and out and getting them patched! Epoxy is too expensive to waste! You will need lots of mixing containers (sour cream containers are good) and plastic spoons for mixing.

    Next, cut pieces of a decent exterior plywood (we used southern yellow pine ply in mixed thicknesses) to fill your excavation in the transom. PLACE THESE WHILE THE FIRST POUR OF EPOXY IS STILL WET!! You shouldn't take more than an hour to do this after you've poured the first batch of epoxy in. It doesn't need to be packed solidly and shouldn't be because you'll be pouring in more epoxy! I'd say our repair had gaps front to back and side to side of less than 10%. NOTE: We dry-fit all of the pieces, numbered and removed them before we did the first epoxy pour. It was only 3 or four pieces total, so no big deal.

    After the plywood pieces are in, pour more epoxy to bond everything together and fill the excavation completely; no voids, no dry gaps. We had to remove the straight edge and the clamps as well as tap shims between the plywood pieces to spread them so the epoxy got into every crevice, then we immediately reclamped the straight edge into place. The plywood will soak up some epoxy, so keep watching/mixing/pouring until it's filled up.

    After a few days of hardening time, we used a belt sander to smooth and shape everything, then reglassed the top edge of the transom, sanded again, painted our work (oil base only!) and reinstalled the aluminum transom cap. Follow Landlubber's directions to redo the motor mount and other holes but I would add this: thicken that epoxy with a healthy dose of Cabosil filler to a spackle-like consistency.

    If you take your time, plan out all the steps, mix and use the epoxy correctly and safely, etc. this should turn out well; ours worked out great.

    If you can't follow directions, have no carpentry skills, have never used a chainsaw or a router, lack confidence, etc. etc.... hire somebody else to do it. Maybe you have a carpenter friend who's willing to learn to use epoxy and fiberglass? This repair has the potential to be a very inexpensive and satisfying success or a total disaster... it's all up to you.

    Here is a good resource:

  11. Garyak
    Joined: Nov 2009
    Posts: 1
    Likes: 0, Points: 0, Legacy Rep: 10
    Location: alaska

    Garyak New Member

    So glad I found this instruction!!...For once I can correct my screw up and make it better than envisioned in the first place!
Similar Threads
  1. Carlazzomark
  2. Bradley Adkins
  3. Reefdog
  4. RSD1
  5. SamC
  6. jangr
  8. Deezil
  9. brokensheer
  10. moka
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.