Thread: Bad transom.

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  1. #1
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    Bad transom.

    My buddy just bought a cobra 201d. Turns out the transom May be bad. Has a little crack just under the 90 degree rail top of the splash well and some brown stains coming out of the tie downs. Also has a couple lines of cracks going side to side in the splash well. During the past few days we’ve been heavily researching Cobras and champions and transom repairs. I know a few have done it with seacast or Arjay. I’m not sure if baking it will help any wet/rotten wood.

    Are there any active members still on here that has looked inside the transom or has done one before? Would be nice to get some tips and tricks. Our plan is to trim the top of the splash well like others have done and dig the old wood out.

    One of the main questions we were looking at was how the stringers were attached to the transom. If we were to get all the wood out of the transom, will there be wood directly going to the stringer where we wouldn’t be able to get at it?

  2. Member
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    #2
    Post this in the bassboat restoration forum on this site. Someone may have done a Cobra and can give you info.

  3. Member hookahawg's Avatar
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    #3
    I had a 99 201 with a similar condition. The brown stains appeared one spring after winter storage, but the transom was otherwise sound. I could stand on the cav plate and bounce up and down and no movement, tongue of trailer would lift of the ground, 6'5" 240lbs. I removed the splashwell drain tubes, tie down rings and even unbolted the j/p with motor and hung it out of the maple in the front yard....and nooo "redneck" don't just belong to you fellars south of the border. Anyway, poked around with a flathead screwdriver in all the through hull holes to find that the damage was limited to a very small portion of each of the attachment holes, maybe 1/8" deep, but enough to get the dreaded brown streaks. I took a syringe and injected all affected areas with antifreeze and let it sit for a day, kills the mold bacteria so I understand.
    Then I put a couple 500 watt halogen construction lights about 2-3 inches from the transom on the outside, centering them to cover all the holes as evenly as possible. Not so close as to burn or delaminate. Covered area with a tarp.
    Gotta be careful, but the gelcoat can take quite a bit of heat.
    I let it bake for a couple weeks until I saw no more humidity being evacuated, (you can best see this at dark when the halogen lights illuminate the very slight "fog" of the evaporation).
    Flooded and resealed all holes with resin, let cure and reinstalled everything with a good marine sealant..NOT SILICONE. I used 3M 4200. All in all, it turned out to be not as bad as I thought.
    I eventually wound up hanging a 250 XB on that hull...no issues whatsoever and scary fast!

    My current 2000 201d also has a couple stress cracks in the splashwell, I suspect that alot of Cobras do, it's that dang square back end that doesn't lend well to flexing.
    It does not concern me as the fiberglass on the inside of the transom where it joins with the knees which then tie into the stringers, has no evidence of compromise, cracking etc. I plan on taking apart and resealing everything as a precaution anyway.

    To answer your second question, yes! My buddy had a 96 201d with a HORRIBLE transom. I mean we thought the motor might just tear away at some point. We did the dig out and Seacast thing on the transom but I believe that the rot had made it's way deep into the stringers which you cant get to from the top of the transom. So while the Seacast may be a good product, you need to remove ALL rot, otherwise simply replacing one section, that ties into an integral part of the structure that is rotten, is just a waste of time and money...and a potential for injury or worse!
    Our repair marginally reinforced and stiffened the transom and he ended up getting rid of the boat.
    Sorry for the long winded...but if this can help you or someone else, great!
    Good luck!
    2000 VIPER COBRA 201D /225 Merc EFI SER: 0T054298
    Where does the white go when the snow melts?

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    #4

  5. Member
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    #5
    hookaway. thanks for your reply. i think this transom is not as rotton but only towards the top half of it. the crack in the splashwell is pretty bad near where the top 2 jackplate bolts go through. looks like it about to pull away. so im sure theres no way of drying out the wood in that area. But now i guess ive found a guy that can hopefully answer some of my questions. lol. ive been reading another guys post in the bass boat restoration forum about a cobra hes done but he must not be active on here anymore. but anyways since youve seen the back of a hollow transom on a cobra my question is this.

    plan is for seacast or arjay.

    on the attached image(not our boat) i plan to cut an opening that is circled in the white. i believe there is wood that goes to the sides where the tie downs are circled in red. my questions is were you able to get that wood out and how? and how far does that wood go to the wide? im assuming it only goes to where the edge is? im just worried about that area. and also the knees? is there any wood in there? Thanks for your help

    IMG_8286.JPG

  6. Member hookahawg's Avatar
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    #6
    My understanding, as well as my personal experience, is that the transom on these boats (non-coosa models) are made up of laminated, fiberglass encapsulated plywood. So it's not just "wood".
    The design is actually quite strong, provided there is no structural compromise...such as rot or weakening due to water infiltration.
    Once again, after you have performed the repair, be sure to seal all through holes with EPOXY resin before reinstalling hardware.
    Epoxy resin adheres better and allows for flexing, while resisting cracking, when compared with polyester resin.
    When I took my '99 apart, all the through holes appeared to have been factory drilled, hole bores left untreated and hardware and motor installed as is, which leads me to believe that the slight infiltration that I experienced was due to the inevitable failure of the marine sealant from flexing and movement, with no second line of defense in the form of thin wall of resin.
    If I remember correctly, the wood/fiberglass laminate of the transom extends about 8 inches beyond the tie-down rings, or to where the rear of the hull has a slight radius and starts to sweep forward to the rounded corners of the back end.
    When we did the repair on my buddy's boat, we took the capping plate off, trimmed back some fiberglass which was hidden by the capping plate, and got at it from there.
    Once you clear a path, you should have upwards of a 3 inch wide slot x the width of the transom to work with. If you remove the section you plan on, you may/should have a little more access to the core of the knees.
    On the boat we did the rot went right to the bottom of the transom cavity. To remove the bad wood, we used a series of long spade bits. Very long and tedious, this will take you at least a 6 pack to complete.
    If the damage to your transom is limited to only a few inches on the upper portion then you may get lucky and save some time as well as a good part of the original structure.
    The stress cracks in the splash-well, vis a vis and just below the top engine mount bolts are mostly cosmetic, but may indicate underlying structural issues further down. You need to get your head in the rear compartment with a good light and inspect the condition of the fiberglass, particularly at the top directly under the splash well, where the fiberglass of the knees ties into the inside wall of the transom.
    Any cracking or pulling away at this area may be evidence of rot having gotten into the knees and may require more tear down and rebuilding.
    Maybe you will get lucky and you will only have a couple inches on the top half to deal with. If that turns out to be the case and if it were me, and this is by no means a recommendation, I would remove the damage on the top portion of the transom, drill a series of vertical holes along the width and down into the sound part of the transom, glue in (resin) some very rigid fiberglass dowels.
    I would also drill some additional vertical holes to allow the seacast, or whatever you choose as a repair media, to flow and tie into the existing transom structure. This will provide a better bond.
    The dowels should act like re-bar in concrete and replace the flexural strength that was removed when removing the bad section of the transom.
    You don't want to drill too many holes as that would defeat the purpose and you will just end up eating away at otherwise solid transom that should be left intact.
    Good luck!
    2000 VIPER COBRA 201D /225 Merc EFI SER: 0T054298
    Where does the white go when the snow melts?

  7. Member hookahawg's Avatar
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    #7
    just deleted double post...
    Last edited by hookahawg; 06-28-2020 at 03:58 AM.
    2000 VIPER COBRA 201D /225 Merc EFI SER: 0T054298
    Where does the white go when the snow melts?

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    #8
    Thanks for your help!!

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    #9
    I’ll post some pics tomorrow. May have another question or 2.