Transom replacment questions

[Gerry B]

Hi guys.
I need some guidance on replacing the transom in a "new to me" 1979 24' Searay. After searching hundreds of post I still have some questions. The motor in this boat was in need of a rebuild so after pulling it out I discovered the transom was shot. My boat ownership and experience has been outboards and inboards. This is my first IO. I have limited experience with epoxy and want to do it right. So, for what I think I know.
I'm planning on replacing the transom with marine plywood sealed with epoxy. Gluing the first piece of 3/4 to the cleaned roughed up inside of the outer skin with resin/wood flour glue. I will hold the first piece to the transom by sandwiching the new plywood between 2x4's using existing holes and some new if needed from the outside of the transom. After that dries I will repeat the process with the 2nd piece of 3/4" prepared and glued the same way. After that dries I can use 12" wide strips of biaxial (1708)? To tie the new transom to the existing bottom, gunnels etc. If I understand correctly, I should do a second pass over lapping the first by 6 inches in each direction. The second pass can be applied when the first pass is still tacky.

My questions
1. The boats deck is molded to the side of the boat. Where the deck meets the transom the space between the deck and the transom is a hair over 3/4?. I cleared that space out after several hours of saw and chisel work. I am considering plugging up the bilge ends of the openings and using the seacast product in that space. The new transom will than be attached to the boat as indicated above. Is this acceptable? The other possibility is to put the first transom piece in place in two sections. Any other options?
2. The old transom wood thickness in the bell housing area was just 1-1/2 inches. The second piece of ? was attached with staples and covered just the bell housing area, not the whole transom. Several posts I have read say the transom should be 2? for the Alpha One outdrive. Do I build it thicker than what it was?
3. The engine mounts have spots on each where it appears it was cut away to make room for the motor and were left open exposed to water. You can see some rot has occurred. Should I open them up and replace the wood or dry the area out and seal with epoxy?

I can post additional pictures. Thanks in advance for any suggestions and guidance. Please also advise on which epoxy, biaxial I should use on the project.

 

[danond]

Re: Transom replacment questions

My site might help a bit. Check the signature.

 

[NickAndJena]

Re: Transom replacment questions

Welcome to the Boat Resto forum at iboats!

You're (and my) problem is quite common. I now have my transom complete and it's very solid. Take a good look at Dan's site so that you may get a good understanding of the process. Most definitely, when you run into a snag or some issue, post your questions or concerns here and someone will most likely provide some very useful advice.

It's hard to see your photos as they are quite small. Perhaps some photos with a higher resolution, or simply attaching a larger photo would help folks understand your situation.

I read into using seacast and then decided it was something out of the question for me, mainly because I couldn't imagine a method of pouring the substance "into" my transom. Later I learned that it would be impossible for application into a I/O transom. I must say, I haven't dealt with seacast so I'm no expert there but doing the transom with the normal method was easy and I'm very happy with the results so far. We're over 1/2 way done with the complete restore that is chronicled on my blog (see url in signature) and it's been interestingly fun so far.

Still more work to do on the stringers and ribs, which is planned for this weekend. Looking forward to seeing some larger (more resolution) photos and learning more about your situation.

Finally, there are a lot of helpful people here that visit and contribute to this site... I'm still wet behind the ears with this boat stuff, but have had a lot of help from this site.

Hope this helps!
Nick

 

[Gerry B]

Re: Transom replacment questions

Thanks for the responses and info.

 

[Bob_VT]

Re: Transom replacment questions

Transom thickness listed here which in our Adults Only tab in I/O repair http://forums.iboats.com/showthread.php?t=311044

 

[Gerry B]

Re: Transom replacment questions

Thanks Bob, that?s a great resource!

 

[Yacht Dr.]

Re: Transom replacment questions

Hello Gerry B.

Transom jobs look intimidating but they are quite simple for the most part. ( expensive though )

Simple rundown of what I would do..

1. Make a template of your transom piece and transfer that onto your ply. ( good to see you using marine grade .. dont bother getting expensive, simple dug fir marine ply is good).

2. I would glue lam with epoxy all your layers of ply before installation. Start in the morning so you can do this all in one day without stopping. For bonding two ply.. Dry fit with fasteners.. take apart and use thinned out epoxy 30-40 % with acetone and saturate the bonding sides of each. when it stops taking the epoxy quickly mix up some thickened epoxy with cabosil. ( colodal silica ). spead it out over one surface with notched trowel and screw those two back together. ( starting in the middle and work your way out.

3. on the transom side of your wood coat with thinned out Polyester resin .. same thing you did before .. but with poly. Once cured and tacky put one layer of 1.5 oz mat on it. Once that cures .. flip it over.. do the same thin coats..then put 1.5 oz mat..then 2 layers of 18 oz mat backed woving. ( or 1708 if not available ). Cut 2 extra Pieces of your 18 oz and one 1.5 oz mat the size and shape for future use.

USE NO WAX IN ANYTHING YET.

4. After that your transom piece on both sided should be slightly prepped with 24 grit then all cleaned up. dry fit that in your boat making sure it does not wiggle or wobble around too much. (might have to grind off some bumps on the skin ). Pilot drill from the outside and dry fasten your ply with 1" x #8-6 pan screws with "fender washers". Cut your 4 layers of 18 oz glass tabs ( side of boat..floor..etc ) in progressive order from 6",10",16" then 24". number each layer with a marker .. 1..2.3.4 etc.

5. mix about a gallon pale of resin and Cabosil and cut up fiberglass mat so its ready to go.

4. Ok..now that you have All your glass cut ( tabbings, 2 pieces of 18 oz and one 1.5 sized for your transom ) time to get those respirators and suits on.. get your whole box of powdered latex gloves.. buckets .. your poly resin..should have a MEKP dispenser ..stir sticks..acetone and an acetone bucket wash..paint rollers.. brushes..your bucket of tiger hair ( resin/cabosil/cut up mat ).. screw gun.. and your best friend .. oh...and a case of beer for the end game

5. Start by resin coat trans skin and apply the 1.5 oz mat that was cut b4 hand on the skin trans....then cat and notch towel your "tiger hair" to the trans ply (a 1/8 " is good enough ). goto your outside and screw your predrilled screws with fender washers working your way from mid trans to outside..when the inside PB is gelling but not hot..go and mix some more PB to fill gaps..then layup 2 layers of your "tabbing" ( # 1 & 2 )..then full layup one of the two layers of your 18 oz "for future use" transom 1708 cloth..then #3 tab..then second full layup of 18 oz across transom..then #4 tabbing..

then pop the beer and relax..any air voids can be handled at anytime after that..( use 1.5 oz mat for most mistakes )

The need for quickness is for you to get both a chemical bond and a physical bond.

This is a "basic" how to on trans replacement.. it is involved and costly..it does not require " epoxy " but requires a sober and devoted person to handle such an undertaking.. PLEASE USE PROPER SAFETY uses of chems and abrasives.. PLEASE UNDERSTAND ALL OF YOUR CHEMS BEFORE YOU TRY THIS... This is why we are pro's .. and have hundreds OR thousands of dollars for tools and safety equip. at our disposal..

Number one without a doubt is BE SAFE !...

Regards.. YD.

 

[ondarvr]

Re: Transom replacment questions

A word of caution on thinning epoxy or polyester resin, even though it seems like a good idea for better penetration its not. Small amounts of thinner (whatever type you plan to use) may do no noticeable harm, but larger amounts begin to degrade the resin rapidly until most of the water resistance and strength are gone. Up to 5% and you won't see a big change, 5 to 10% and you'll see more, after about 10% (it will be different for each formula and type of resin) the physical properties start dropping faster. At 40% you no longer have even near the strength you did to start with. Pre-coating the wood is the most important part for a good bond.