Transom repair

M

marykhubby

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25522
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1968 Larson, merc 120 I/O, 17' fiberglass hull

Transom housing seal has been leaking. Old gasket is cracked and dried out. I pulled the engine forward to get at the housing and, you guessed it - the lower 1/3 of my transom is kaput.

I've used my dremmel to cut away the glass around the transom edges and removed most of the dryrot material behind the interior glass shell. Now the outer hull is exposed.

Should I continue to remove and replace the entire wood transom, or carefully cut away about 1/2 way up and only replace the lower section? Would I be sacrificing any strength that could prove to be a risk given the small 4 cyl engine?

If I do go the route of replacing the entire transom, where could I pick up a transom template to assure I get it right?

Thx
Don
 
Transom repairs that i've seen done were done from the inside. The exterior fiberglass was left in place, and rotten wood was removed from inside. Of course, engine and anything in the way must come out. You need to make your own transom. It must be coated with resin between the layers to keep it waterproof. The new transom must be structurally sound on boats with i/o's. inboards are really not that critical, since there is no stress on the transom.
You are the only one that can determine if its even worth doing on that old of a boat.
Let us know what you decide.
 
It is worth it.

This boat has 200 actual hours, original seats and canvas, garaged all it's life, and was purchased new by my now deceased father. I learned to ski on this boat and completed my original Power Squadron certification with it. It is the reason I own 3 other watercraft today... A great boat that requires a little TLC now and then (not unlike what everyone else experiences who owns a boat). I have decided to repair it.

Back to my original questions for you experts ...
1). Is it sound practice to only replace part of a transom on an I/O? (I don't like "half-a$$ed craftmanship but also am practical)

2). Where can I obtain a transom template?

Thx
Don
 
I've done one on an outboard and made a new one as described by GSent. I don't think filling your cavity with epoxy or other products is a good idea but others may disagree, as the transom has little stress with an I/O.
But if you can do it that way, it'll prolly save lots of time and labor.

What I did was make a new one from scratch, (2- 3/4" marine ply) glassed on both sides and in the middle, and glassed it in place with woven roving and matting. "Overbuild" was my guide. Bought 2 special rollers for working the laminating resin into the corners and base. And, if you go this route, use laminating first for strength, finish with regular resin, either sanding or finishing.
I destroyed the original transom when removing it, (horrified the Admiral when she saw it) so had no template to work from. By that I mean a cut around the end of the hull, completely removing the old transom. It was damp rotted thru and thru. Fun!

An I/O will be more difficult to duplicate the hole, so try to make a template first. You may be able to find a pattern on the web also..
BTW, that is what you mean about transom template---the I/O drive hole?
 
Yes
I assume a template would provide exact dimensions of the I/O hole and it's position relative to edges and bolt thru holes. I have not completely dropped the external housing assy yet but may end up doing so. In that case the hole would be easy enough to trace on cardboard.

I was just hoping someone could steer me in the direction of an inexpensive template before I ripped into her further (trying to think ahead).

Next it is time to scour some lumber yards for marine ply...
 
Called around today.
Prices for Ply were all over the map ($75-$120), and very few had any in stock. Located 3/4" Marine Ply grade AB at MENARDS for $75/sheet. I have decided to go "all in" on replacing the full transom instead of cutting her in, and bought 2 sheets.

Next steps will be to trace / measure / photo as much of the pattern features as possible. I'll drop the external housing while I am at it. Then resume the tear out!

I am beginning to see why this is such an expensive job to outsource. Labor intensive. No big deal, I have her in the garage where I can turn on the heaters, and I feel like it's summer again in MICHIGAN... (got to get my SUN-fix somehow)
[8D]
 
take your time, enjoy the process, it's not that bad once you get the old one out. Oh, wait, laying up the fiberglass..
Rough sand the plywood before laminating together. Sand everything before laminating. Don't sand laminating resin-it doesn't sand!
There should not be much sanding of cured resin and f-glass, (my least favorite thing), but there's ways around that, too. Tyvek suits??
Have you done much fiberglass lay-up? It's not rocket science but there is a right way and a wrong way.
Either way, a good reference source is publ.#002-550 from west marine, "Fiberglass Boat Repair & Maintenance", under $5.
Keep us updated, post a picture...
Buzz
 
Another good resource is "Runabout Renovation: How to Find and Fix Up an Old Fiberglass Speedboat" by Jim Anderson. $12 on amazon. If you plan to keep the boat do it right...you definitely will not want to repeat this job after you do it once.
 
If you plan to keep the boat do it right...you definitely will not want to repeat this job after you do it once.

AMEN to that
 
WOW. Yesterday was a back breaker taking out the old transom! Loving Ibufprofen right now...

When only 1/3 of the bottom is soft, the upper 2/3 does not like to go anywhere without real effort. But she's out now... I also decided to R-R about the last 2-3 feet of floorboard (getting soft too, and it will be easier to properly seat the bottom of transom). Everything north of that is solid. Dropped the I/O housing too, and cleaned off the old gasket area. Good time to apply BuffMagic and PP while I have everything off.

I do have a question - Are stock hydraulic replacement lines easy to find (where)? Mine are all brittle and losing their cover so it's time to get that right too. Might need Kenny's "service know how" on this one...

Going in should be a lot easier on the ole back - I think the physical part is behind me. Now to take my time and get the rest right. I am taking pic's along the way so when I get time I'll post them.

And to think I went in thinking this was a GASKET RR job!!! HA!
Don
 
pickle the new with CPES. Had the mfg done this originally, you would not be doing this today. Not a knock, nobody does it.
 
I am not familiar with CPES but this is the 3rd recommendation I have seen since researching this job. I assume one treats the wood with this instead of sealing with normal resin. I wonder how the preparation for CPES interfacing with fiberglassing works....
 
CPES = "Clear Penetrating Epoxy Sealer" ( trademark )

Essentially, it is an epoxy, formulated to be very "thin" and capable of penetrating wood more easily then standard epoxy formulations. Though it has some structural strength, I suspect that that strength is much lower than standard epoxy formulations. It is mainly used for penetrating rotted, but dry wood as part of a restoration.

What Ghost is describing is essentially turning your plywood into a block of "cellulose reinforced plastic". This would make the new transom resistant to water intrusion, in the event things are installed improperly and not sealed correctly.

Imho, this is an unnecessary step. The CPES will add expense and weight ( as well as labor ), and if you maintain your vessel correctly, it would provide little to no additional benefit. YMMV.

DO be sure to seal the finished project correctly, and make sure to properly prep and seal all intrusions into the transom...
 
Next step... (been doing more research)
I see various type mats and weights offered (1208, 1708, woven, biaxial, blah-blah-blah).
Which fiberglass material(s) is best for this application, when used with an Epoxy
Resin? (fyi - I am going to reglass stringers while I am in there too)

Does it matter which type resin I seal the transom with (epoxy, polyester, or other)?

Various epoxy products are available - what experiences have you had (ie., System Three, Solarez, West System, Resin Research, or MAS Epoxies)?
 
according to what i've read here, epoxy resins don't bond well w/ regular boat polyester resins. I think epoxy is not nesessary for the transom, but maybe for the stringers. But it is more involved.
Charlie, (jtybt) has done stringer replacment and described it well here with pictures, maybe he can jump in. You should check into one of the above mentioned books--it's worth knowing what you're doing.
Are you familiar with fiberglass layup?
Too much resin, no strength. Too little, it's a dry glass job, air enters the fiberglass lam, = no strength in the layup.
Glass cloth is good for initial layup, 8-10 oz. couple of layers, matting is ok and easier to work with, makes a good second layup. Not familiar with biaxial, but regualr F/G cloth and matting is my choice. Along with polyester resin.
When repairing always rough sand the area to be glassed, wipe w/ acetone. Using laminating resin for glass layup will help bond the parts better. Sanding or finish resin dries brittle enough that the glass will delaminate under stress, even very little, as in crusing thru rougher than normal water, because of lack of bonding to other sanding resin.
Stringer repair, get the booklet I mentioned.
Any finish resin is fine for sealing transom, provided it is well sanded first.
Buzz
 
No - not familiar with it, but mechanically inclined, reading, and asking questions... (does not appear to be rocket science from what I've read, but then I am not an astronaut either)

I've found I am not afraid of any of the jobs I've taken on with the insight of the experts here.
 
I like the 1708. I think it would be fine for both stringers and transon. And any of the resins you said will be fine also. I used West and Mas Expoies but I can usally get a less expensive here local as there is a large fiberglass product shop close to me.
Google fiberglass coatings inc. You can check prices and they have a nice DYI help section.
 
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