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Catalina/Capri 25/250 Sailor's Forums

Catalina 25 Specific Forum

transom work

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karentc
1st Mate

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USA
68 Posts

Initially Posted - 06/02/2003 : 20:50:05

Hi!
I am upgrading my motor to a 4 stroke and am in the process of sturdying up the transom with a 1/4" thick aluminum plate under my motor mount on the inside of the transom (starboard side). At the same time I discovered that the fiberglass had shattered under my swim ladder mounts where they attach to the fiberglass on the port side. I was just getting ready to attach a similar 1/4" thick aluminum plate on the inside of the transom and when I took off the ladder it looked like there was a hollow core rather than the plywood I was told that Catalina put in the transom... Moondance is a 1986 C-25 fixed keel. Does anyone have any information about the core of the transom and if it is hollow any suggestions on filling it before I attach the steel plate on the inside?? HelP!!! I really want to get her into the water!!!
Thanks,

Karen Christensen
Moondance
Grand Traverse Bay, Michigan

Edited by - on

Bill Holcomb
Admiral

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USA
769 Posts

Response Posted - 06/02/2003 : 23:49:12

Hey Karen,

The chances are that the transom itself is solid fiberglass. Probably 5/16" to 3/8" thick. Then, the interior liner is also solid fiberglass about 3/16" to 1/4" thick. The production process was to lay up the hull, the interior liner and the deck. Then, epoxy the interior liner into the hull. And then fasten the deck/cabin structure to the hull (thereby covering the interior liner.

The hollow nature of the transom is caused by a void between the hull and the interior liner.

Bill Holcomb - C25 Snickerdoodle #4839

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MikeM
1st Mate

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72 Posts

Response Posted - 06/03/2003 : 08:45:20

I just drilled a hole in my transom for bilge pump outflow (thru-hull). I drilled through a thick wall of fiberglass (outside) and a 1 inch? marine plywood core and fiberglass (inside).

I am surpised that you would find a pocket in the transom.As Bill mentioned must be a void issue, between the liner and core.

Mike M
Marblehead, MA
C25 #1212

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karentc
1st Mate

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USA
68 Posts

Response Posted - 06/03/2003 : 09:12:45

OK, so how do I fill the void???
I still need to stabilize the fiberglass under the swim ladder...
And an aluminum plate on the inside won't help if the void is close to the surface of the outside fiberglass... Help!

Edited by - on

OJ
Master Marine Consultant

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USA
4382 Posts

Response Posted - 06/03/2003 : 14:45:14

Hello Karen,
I am painfully aware of your dilemma. Even before I installed my 9.9 four-stroke I had problems with the transom bowing.
While I don't think I had any voids, my transom was bowing to the point that the gel coat was cracking. I tried various types of backing plates to no real avail. If I remember correctly, I only encountered plywood in the upper half of the transom.
My solution (one that is borderline extreme but 100% effective) was to reinforce the transom with fiberglass. I ground the gel coat off inside and out where I wanted to add strength. Applied several layers of fiberglass cloth inside and out and re-gel coated the transom exterior. Transom looks better than new and is straight as a board even with the motor mounted - very, very strong.

Edited by - OJ on 06/03/2003 15:19:38

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Dave B
Admiral

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Mali
863 Posts

Response Posted - 06/03/2003 : 22:59:31

Hi Karen...

My '85 has a foam core between the transom and the liner. I found that out when I drilled for my new outboard bracket--the foam grabbed the bit and practically pulled the electric drill out of my hands!

My approach to strengthening involved using pieces of 1/2" Starboard on the inside and outside of the transom. The bracket is on top of a piece that spreads the forces, particularly below the mount. I used two smaller pieces inside, to help conform to the increased curvature of the liner.

If you're not familiar with Starboard (sold by West and others), it's a polymer board that you can work with woodworking tools--power and hand. I cut it with my circular saw, shaped it with an orbital sander, and drilled it with an electric drill. It's UV resistent and obviously weatherproof--maintenance free. (Not cheap, but a good investment.)

Dave Bristle, 1985 C-25 #5032 "Passage" SR/FK/Dinette/Honda in SW CT

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Gary B.
Admiral

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USA
969 Posts

Response Posted - 06/04/2003 : 13:14:14

Karen: Mine is a '78 swinger, also with a "void" between the hull, proper, and the deck, or in this case, cockpit. I know we have slightly different designs, but I was able to mount a new, heavy motor mount with the backing plates BETWEEN the two "walls" , if you will. My mount is on the portside, with the top two bolts being accessible in the deep locker.

I don't know if Catalina made weaker boats after '78, but I have had a HEAVY Yamaha 9.9 fourstroke hanging on that sucker since 1985, or before, with NO gelcoat cracking, etc. I just got done putting some oversized fender washers (3 inch or so?) under 2 of the upper bolts and large washers, just for insurance, but there was no real need. One had to be creative and flexible to reach the nuts in the "void", but my gas locker provided upper access, and the lower "covered hole" at the stern end of the quarterberth provided access to the lower bolts. I simply plugged the two old, unused holes from the old mount with caulked bolts, nuts and washers. You can't tell, as the new mount basically masks them from view. Hope this helps somehow.......

Gary B.
Encore! #685 SK/SR

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The Officers, Staff and members of this site only provide information based upon the concept that anyone utilizing this information does so at their own risk and holds harmless all contributors to this site.