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Catalina/Capri 25/250 Sailor's Forums

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Outboard bracket installation

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sweetcraft
Admiral

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USA
816 Posts

Initially Posted - 08/28/2004 : 01:02:08

What are the things to look out for when changing bracket for a 4 cycle outboard. I have the one from Catalina Direct for a extra long shaft Honda. Putting it on a 79 C25.

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ClamBeach
Master Marine Consultant

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3072 Posts

Response Posted - 08/28/2004 : 10:59:51

IMHO follows:

For a Bristol installation I'd sandwich the transom by putting oversized backing on the outside and inside of the hull. Make sure it's well bedded with 3M 101 or 5200.

I used 5/8" Teak finished with Cetol for the backing on the outside... it extends out a couple inches beyond the mount base. Inside I used home-made hi-moly (industrial plastic) backing washers with fender washers. Really stiffened things up. I went up a size on the bolts too.. 3/8" as I recall. Nylon locking nuts are a must.

On anything of this nature, be sure to radius (round off) the corners of the backing plates to prevent concentration of stress and cracking. (Everything on a boat should be 'rounded)

On my boat (with the Garhauer Mount) the top of the engine mounting board is between the rubrail and top of the transom when the mount is in the fully elevated position.

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Dave Bristle
Master Marine Consultant

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Djibouti
10005 Posts

Response Posted - 08/28/2004 : 11:47:33

I also "sandwiched" the transom (nothing to do with my name), but with 1/2" Starboard (plastic board available in most chandleries) inside and out. On the outside, I extended it well below the bracket (although not a lot wider), and on the inside, as much above as possible. That matches up to the stresses from both weight and thrust.

The rounding that Clam mentions is particularly important on the inside, where the concave shape can cause the corners of a board to contact first. Actually, I'm inclined to recommend a thinner plywood on the inside--maybe 3/8"--to better conform to the concave curve. Size and a little flexibility are more important than thickness on the inside. If you need more clearance for tilting the Honda, you can even use multiple layers of Starboard on the outside.

Edited by - Dave Bristle on 08/28/2004 11:49:00

Leon Sisson
Master Marine Consultant

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USA
1893 Posts

Response Posted - 08/28/2004 : 14:44:30

<center><b>Motor Mount Attachment To Transom</b></center>

Jim,

Here's a repost of my answer to a previous question about installing an outboard motor mount on a C-25. I also have a 1979 model C-25. I think you need to pay particular attention to the hull liner to transom gap issue with the early model C-25s.

Where my retractable outboard motor bracket attaches to the transom, I have the following reinforcements. My 1979 C-25 transom came from the factory with about 1/2" plywood core but no inner fiberglass laminate. Where the motor mount is located, the inner hull liner has a natural gap of maybe 3/8" to 3/4" from the transom plywood. There is now a large thin plate of stainless steel between my motor mount and the transom (outside). Inside, I used a large holesaw to cut away the inner hull liner around each of the four motor mount bolt holes. I then used the same holesaw to make up 3/4" thick plywood cookies to fit the holes in the liner. After saturating the cookies with epoxy, I installed them in the liner holes with epoxy and milled fiberglass mush. It's significant that the cookies be thick enough to more than fill the gap between the liner and the transom so that, with the generous addition of the epoxy mush, the cookies tie the liner to the transom at the motor mount bolt locations. After the mush cured, I redrilled the mount holes oversize, and refilled them with liquid epoxy thickened with more milled fiberglass. Duct tape was used to form an outer mold wall and an inner funnel to contain the epoxy while it cured. Finally, I redrilled the motor mount holes in the hull and reattached the mount assembly, bedding the bolts with polysulfide sealant.

So far, so good, and I use a 10HP extra longshaft high-thrust engine. I've put over a thousand miles on the modification without incident. That includes a couple hundred miles in the open ocean. The transom doesn't appear to be flexing at all.

-- Leon Sisson

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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.