getting ready to fix my transom...need some advice.. PICS ADDED

M

michael barnes

Active member
some of ya know, the previous owner of my boat replaced about 8 bolts in the transom of my starcraft with steel bolts, and they corroded all around each hole. the corners of my transom are fine, and the 3 triangular braces at the bottom are very solid, so i think ive got plenty to work with. the total thickness of the transom originally was 1.5" plus about .125" for the aluminum. so i have 2 questions
1) should i run a 6" wide strip of aluminum across the transom, to cover the eaten up bolt holes, and put two sheets of .75 plywood on the inside like it was originally?
or could i put a sheet of .75" plywood on the inside, then one on the outside, sandwiching the the aluminum transom, and use big washers around the bolt heads and nuts? i would like to keep it as cheap as possible, but i want it to work.
2) what should i use for bolts to avoid anymore corrosion?
thanks, mike.
starboard side
105_5059.jpg

port side
105_5060.jpg

the large holes are from a copper tube put in for a bilge pump hose.
the entire transom has pitting and corrosion, but around the bolt holes is where it is worse.
 
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Michael,

Post pictures of the damage. GIGO Garbage In Garbage Out The advice you get will only be as good as the information you provide. Is there structural damage? It doesn't sound like it. What is the diameter of the corrosion around each bolt hole. Can it be covered with a SS fender washer bedded in 5200? Site unseen yet, I would recommend the 2 - 3/4"sheets inside the the transom but you may want to add a 1/4" sheet on the outside making a sandwich of the aluminum. My Wolverine had a thin sheet of marine ply in the motor mount area. If the corrosion is in that area the thin sheet would work great.

Give us something to go on,
Scott
 
yes sir, ill have pics up tomarrow. just guessing, id say the corrosion spots are 2" dia. ill get some pictures up of the whole transom and closeups of the holes tomarrow. thanks, mike.
 
Based on the pics, this is definately fixable. These old boats are tougher than you think, this looks more cosmetic than anything.
I like Scotts idea of two sheets on the inside & a thin sheet on the outside.
I'm not sure about fasteners, I will leave that to someone else.
 
Hopefully someone with a bit more experience like Lou will add their comments too but my thoughts are "she ain't bad". I'm not sure if the pits are due to the fasteners or if they used a sealer that isn't compatible with aluminum. Many of the common home caulking and sealers are not compatible. Always verify on the tube that your sealer is acceptable for aluminum siding and windows.

Anyway all the pits and holes appear to be above the water line and your transom looks solid. Your planing on using marine ply. I'd simply use a quality marine sealer (not an adhesive), squeegee a layer on the transom to fill the pits and holes,and a coating on the wood. Install the plywood on the inside. Use stainless Fasteners, I'd add washers on the outside under the nuts to better distribute the load. Tighten each fastener in rotation a few times to get the sealer squished out even Use clamps in any area that the screws are not getting to. You do not want any air spaces left between the transom and wood. Ideally the sealer will be squirting out any holes and around the edges.

Good luck!
Scott
 
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i think your right about a sealer or something else also causing it. the entire transom has some pitting and thinning, everything touched by the wood. then under where the wood was, it stops completely. im getting excited about fixing it now, and i appreciate all the input.
 
i think your right about a sealer or something else also causing it. the entire transom has some pitting and thinning, everything touched by the wood. then under where the wood was, it stops completely. im getting excited about fixing it now, and i appreciate all the input.
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Was the plywood pressure treated?
 
Hopefully someone with a bit more experience like Lou will add their comments too but my thoughts are "she ain't bad". I'm not sure if the pits are due to the fasteners or if they used a sealer that isn't compatible with aluminum. Many of the common home caulking and sealers are not compatible. Always verify on the tube that your sealer is acceptable for aluminum siding and windows.

Anyway all the pits and holes appear to be above the water line and your transom looks solid. Your planing on using marine ply. I'd simply use a quality marine sealer (not an adhesive), squeegee a layer on the transom to fill the pits and holes,and a coating on the wood. Install the plywood on the inside. Use stainless Fasteners, I'd add washers on the outside under the nuts to better distribute the load. Tighten each fastener in rotation a few times to get the sealer squished out even Use clamps in any area that the screws are not getting to. You do not want any air spaces left between the transom and wood. Ideally the sealer will be squirting out any holes and around the edges.

Good luck!
Scott
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As far as something to seal/attach the wood to aluminum, if you want to so that route - you could use 3M 5200 to attach a sealed wood transom to the metal.. It is available at all marine stores, you could probably get by with one caulk tube full. Clean-up is mineral spirits before it sets, working time is long and it is strong. often wood transoms aren't bonded, but in this case with the eroded metal, maybe that would be a good idea. Polish up the metal with a wire brush before application (per our resident aluminum expert).
 
i dont think it was pressure treated, it was rotted to mush in several spots, but i guess it could have been. will treated ply rot over time?
 
treated plywoood will rot given enough water exposure over time. The bigger problem is that the preservatives in it can reallly eat metal, dont use pressure treated in you fix. Use marine plywood.
 
Michael -

Will you be in salt water? As for patching, good ideas mentioned above. You might also consider going to your local scrap metal yard. They will usually allow customers to roam to find some scrap. Find an old road sign of the right dimensions, grind off the "sign" side and have that welded on the back side. More of a watertight seal and adds some integrity to the existing aluminum sheet. You might even find a piece of AL angle (2"x2") that you can weld across the outside top. The angle would give additional structural integrity to the transom, would give something for the top of your motor to rest on when you set it down on the transom and would keep some water from getting between the aluminum transom and the top of the plywood inner. Just some thoughts.
 
Michael -

Will you be in salt water? As for patching, good ideas mentioned above. You might also consider going to your local scrap metal yard. They will usually allow customers to roam to find some scrap. Find an old road sign of the right dimensions, grind off the "sign" side and have that welded on the back side. More of a watertight seal and adds some integrity to the existing aluminum sheet. You might even find a piece of AL angle (2"x2") that you can weld across the outside top. The angle would give additional structural integrity to the transom, would give something for the top of your motor to rest on when you set it down on the transom and would keep some water from getting between the aluminum transom and the top of the plywood inner. Just some thoughts.
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Aluminum angle or channel works well and can give the job a finished look. It will also protect the top of the transom from wear if you dont' have some sort fo trim piece salvaged from when you took the transom off.
 
Just this morning we opened up a transom that looked this bad.

If you're running in saltwater, cut it out & start with fresh material.

If you're running in fresh, I'd still cut it out.

Just looking @ the pic's, you could cut a (2) two inch border all that way around the transom & re-attach the new material to that.

This way you're not getting into the gunnal rivits.

Since you're down this far, I would also skip the marine plywood for the transom & use starboard.

We replace all transom wood with the starboard nowadays.

It never rots, it's stronger than plywood, water has no effect on it & it doesn't interact with aluminum.

If you decide this route, there are several places in Ft Lauderdale that ships.

Ebay is also another great sorce.

SKIP THE PLYWOOD!!!
 
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Michael,
Scott is onto something here. Whatever bolt you use bed it with 5200 and even with stainless you are going to have some dissimilar metals issues. 5200 bedding will slow down the corrosion some but you will still need to keep an eye on it. Also make sure that you install sacrificial zincs several places on the hull. I would put a thin plate of aluminum on both sides of the transom. Also get a rubber transom quieter thingy to cover the aluminum with. It will cause at lot less transom rattle noise. Also instead of plywood why not Starboard wood as it isn't supposed to rot ever.

Best of luck,
Harry
 
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I had to do the same repair on my starcraft, all the previous advice hear was great.M y fix was a street sign cut to shape inside the boat fastened with 5200. I did not have access to welding equipment so I cut to shape with a jig saw. I replaced the plywood with marine ply. the whole project was less than a hundred bucks. The starboard is a great idea but for me the marine ply was at the local lumber yard. By putting the metal inside the boat I was able to do all the work myself without any tools other than a jig saw with a metal blade. Hope this info helps.
 
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