[3car]

I need to replace the transom in my 21' Sylvan, and I'm not sure which type of plywood to use. I've read that treated wood will cause bad corrosion problems in the aluminum. Any suggestions?

[Bob_VT]

3/4 " plywood just not PT. You will have a fairly easy transom rebuild and the hardest part will be properly and completely sealing the plywood with resin.

[26aftcab454]

3/4" Marine Plywood-mines 3 sheets glued together with wood screws & bolts been fine since 1994.
paint or sand & stain . back in1994 a 4x8 sheet was $56. the LoneStar has a 1994 115 Evivrude

[3car]

Originally Posted by Bob_VT

3/4 " plywood just not PT. You will have a fairly easy transom rebuild and the hardest part will be properly and completely sealing the plywood with resin.

Marine plywood or just standard plywood? Do you screw the peices together and then laminate them?

[3car]

Originally Posted by 26aftcab454

3/4" Marine Plywood-mines 3 sheets glued together with wood screws & bolts been fine since 1994.
paint or sand & stain . back in1994 a 4x8 sheet was $56. the LoneStar has a 1994 115 Evivrude

no fiberglass?

[Bob_VT]

3/4" exterior or marine plywood. I use gorilla glue to glue the pieces together and clamp with screws..... when dry I remove the screws.....

Use fiberglass resin and yes seal all the surfaces. You can put a layer of fiberglass matt on that will add strength. If you use fiberglass resin I would suggest a layer of csm chopped strand matt with it.