transom replacement 21 ft alum boat

[Andy in NY]

Re: transom replacement 21 ft alum boat

ya you should ditch the poured in and go with sheets of foam board.


deck thickness is subject to many debates. i used 1/2 and am not happy, seems kinda flimsy. some say 3/4 is overkill and the added weight is a minus. i would go with at leadt 5/8, if not 3/4. use regular exterior grade ply and seal. if you use epoxy then there is no need for glass, but if you use poly resin then coat the bottom and sides and then glass the top.

 

[fishcrazy50]

Re: transom replacement 21 ft alum boat

Hello. I joined iBoats just for this thread. I have this same boat and redid the transom and deck 2 years ago this month.

I used Marine Plywood for the transom, 3/4 and glued the two pieces together using West System and one of their fillers. I also screwed the pieces together to make the 1.5" thickness. I used exterior grade plywood from a lumber yard for the deck and wish I would have used it for the transom as well due to its lower cost, yet almost same quality. I bypassed the HD and Lowes plywood as my local lumber yard sells a higher grade at a lower price. There was very litt difference between the marine and exterior grades. I only found two small voids (very, very small) in the exterior grade. The 3/4 marine was $84 while the 1/2 exterior was $24. I sealed everything with several costs of West system epoxy resin.

I riveted the flooring in place then covered with Nautolex using exterior porch cement. It's holding up very well. The downside to porch cement (for carpeting) is it's thick and must be troweled. Use a heavy J Roller to smooth it out. I would rather of used 3M aerosole but could not find it in a waterproof version. I am in an area where aluminum is a rarity so could not find anyone to put the heavy cherry or mushroom rivets in at the motor well. I used poprivets from a local military surplus store near my home. They are holding up very well.

In retrospect I wish I would have gotten a taller console to replace the stock one. I could not find one cheap enough until after I finished the boat. Too late then as the steering cable and other wiring was run.

I did not remove the old foam, but let it dry out for 6 weeks with a fan blowing on it. (It had filled with water while sitting at my parents place)

If you would like me to email you photo's of the process send me your email addy.

One thing I forgot to mention was in gluing to 3/4 pieces together for the transom, I had a lot of sanding with a belt sander to get it to fit in place. I did not go with a 3 piece transom as Starcraft did but one single piece. That's how my transom rotted in the first place. They do not seal wood except with a product similar to Thompsons, and water colleted at the unsealed seems. My last time out, the engine broke the keel brace. No problem as a friend is a welder at the local shipyard and welded in a heavy piece of billet. I bought a 1/4 shet of aluminum to place in the transom but didn't use it. trying to fit 3/4" wood and 1/4 " aluminum wasn't adding up without adding in a 1/2" plywood or doubling the aluminum plus a 1.4" of wood. Too much to make that happen. With the grade of wood I used and sealing it with West, it will outlast me any way.

Let me know how I can aid you.

John

 

[fishcrazy50]

Re: transom replacement 21 ft alum boat

Oops, wrong thread, but still on target.

 

[Andy in NY]

Re: transom replacement 21 ft alum boat

Hello. I joined iBoats just for this thread. I have this same boat and redid the transom and deck 2 years ago this month.

I used Marine Plywood for the transom, 3/4 and glued the two pieces together using West System and one of their fillers. I also screwed the pieces together to make the 1.5" thickness. I used exterior grade plywood from a lumber yard for the deck and wish I would have used it for the transom as well due to its lower cost, yet almost same quality. I bypassed the HD and Lowes plywood as my local lumber yard sells a higher grade at a lower price. There was very litt difference between the marine and exterior grades. I only found two small voids (very, very small) in the exterior grade. The 3/4 marine was $84 while the 1/2 exterior was $24. I sealed everything with several costs of West system epoxy resin.

I riveted the flooring in place then covered with Nautolex using exterior porch cement. It's holding up very well. The downside to porch cement (for carpeting) is it's thick and must be troweled. Use a heavy J Roller to smooth it out. I would rather of used 3M aerosole but could not find it in a waterproof version. I am in an area where aluminum is a rarity so could not find anyone to put the heavy cherry or mushroom rivets in at the motor well. I used poprivets from a local military surplus store near my home. They are holding up very well.

In retrospect I wish I would have gotten a taller console to replace the stock one. I could not find one cheap enough until after I finished the boat. Too late then as the steering cable and other wiring was run.

I did not remove the old foam, but let it dry out for 6 weeks with a fan blowing on it. (It had filled with water while sitting at my parents place)

If you would like me to email you photo's of the process send me your email addy.

One thing I forgot to mention was in gluing to 3/4 pieces together for the transom, I had a lot of sanding with a belt sander to get it to fit in place. I did not go with a 3 piece transom as Starcraft did but one single piece. That's how my transom rotted in the first place. They do not seal wood except with a product similar to Thompsons, and water colleted at the unsealed seems. My last time out, the engine broke the keel brace. No problem as a friend is a welder at the local shipyard and welded in a heavy piece of billet. I bought a 1/4 shet of aluminum to place in the transom but didn't use it. trying to fit 3/4" wood and 1/4 " aluminum wasn't adding up without adding in a 1/2" plywood or doubling the aluminum plus a 1.4" of wood. Too much to make that happen. With the grade of wood I used and sealing it with West, it will outlast me any way.

Let me know how I can aid you.

John

welcome to iboats!

personally i think it was a problem to leave that old foam in place for 2 reasons

1) as previously stated it blocks the drainage

2) old foam absorbs water (your case prime example). new foam wont hold it in at all due to its closed cell construction

 

[timfives]

Re: transom replacement 21 ft alum boat

I would remove it all, even if it is dry now, it has the potential to hold water in the future. Putting in foam boards or the like will allow the water to make its way to the bilge and infinitely prolong the life of the new floor and transom.

T

 

[sprintst]

Re: transom replacement 21 ft alum boat

My foam looked dry too. In the end I pulled a couple of hundred pounds out as it was saturated in spots. I also covered up corrosion and rivets for the stringers that were broken, etc.

I took a piece of wire through all that pathways that water could drain and opened them all up.

It was the only was to go to get at the seams to hit with Gluvit. Not a drop of water made it out after a leak test...