transom time

[JimCt]

Mako254,

If I read you correctly, the effect of the rotational force would put the two gunnel/transom points be in tension, correct?  With the "lever effect" of the motor weight, transom failure, I'd guess, would start with the transom peeling away from the gunnel.  But, as we both appear to agree, the way these transom jobs are done seems to work, apparently.  I've never heard of a catastrophic transom failure.  Maybe it's just kept quiet...

I'm a bit backward and old school; I need re-assurance about things which likely could cause a sudden & unpleasant adventure.

[Mako254]

I looked back at some of the photos and had some other thoughts.

I think he raised the stringer height in the stern, either side of the live well.  I noted this as my 254 has a gutter, stern.  It's not much but I bet it's 4" total. Hencethe bracket is set lower and spreads the force along the width of the beam. It also looks as he used the added stringer height as a mounting point for the bracket. I think it's starting to make some sense. If this is the case I see no issues even with 370 hp of 4 strokers

[JimCt]

As long as there's some beef to the stringer ends, that certainly helps.

Well, when I get into my transom job I'll give you a shout.  I'm right down the road in Haddam.

Enjoy the snow.

[Mako254]

http://www.systemthree.com/links.asp

[Mako254]

You might want to try this one as well.

http://www.minicraft.com/

[Mako254]

Sorry for the multi posts... slow day

http://www.dynagrout.com/index.htm
http://www.boatdesign.net/Directory/Mat ... and_Resin/

[RickK]

Boy, those links ought to keep Jim busy for a while  
Jim, is your transom getting weak or has winter set in and you're just curious?
I don't have to replace mine (yet), (even though there are a lot of screw holes from one side or the other, plugged/patched/filled on it) but I am curious.  I would presume that you would glass everything to every stringer, hull side, anything to get more support.  AND multiple layers, each being scruffed/ground and the next being longer than the previous.  I'd probably go overkill being afraid of losing a 5k+ (10k, 20k+) motor.

[JimCt]

Yup, looks like I've got some homework assigned.

My transom appears OK, no flex or anything with the motor bounce test, but after 30 years there's possibly trouble a'brewing.  Think maybe the transom should be addressed before it loudly and expensively addresses me.

I know water has gotten in there because I had a mysterious leak when I bought the boat.  Turned out the deck drain thimbles were un-seated when the previous owner mounted the new Merc the year before.  The motor clamp bracket pressed the thimbles inward, maybe .100", which was enough to break the seal around the thimble O.D.'s.  Water came into the transom core then drained into the bilge area.  Leak rate was over a gallon an hour.  I stopped the leak with a few dabs of 5200 but there's no way the wood core can dry out.  The Rot-Clock is ticking.

That being said, yes, winter has set in.  Mowing is over with and with time on my hands plans & to-do lists are breeding like rabbits.  Since my experience has been solely with wood hulls, this transom to-do item is new ground for me.

What maybe I'll do is pull the motor and, from the inside, open the transom up around the drains.  If the core checks out sound but simply wet, I'll be out of the woods.  I'll let the core dry out and re-glass it.  But if there's a peat bog in there the whole thing will have to go.  We'll see.

Side item:
When I linked over to the Mako site to look over the transom rebuild post, I found  the combination of running commentary sprinkled in with pictures very effective.  Here, when someone is describing their boat or project, I find myself jumping back & forth between the gallery and the forum and trying to keep what I'm reading in sync. with the pictures.  Are we set up here so pictures can be embedded in with verbal posts?  Guess maybe Captain is the go-to person on this but with the new baby about due soon, that can wait.

[warthog5]

I may be able to shed a little light here.

The inner laminate is wraped onto the side and bottom of the hull with each aditional layer of glass. Knee's are installed to help transfer the load to the stringer's. The floor is then tied into the knee's forming a box. The topcap is tied into the top of the transom and the side's of the boat.

The bracket's with large swim platform's actually work to disperse the load over a much larger area and a large tub/body help's to offset the weight of the motor/motor's at rest.

Hope that help's. :)

[JimCt]

A "little light"?

Heck, that's a glaring 1,000,000cp spotlight!

It makes sense now.  So what you're saying is that there is a complete box structure in there?  That'll work for me.

[warthog5]

JimCt   I can only show you how mine was done and I belive Wilson's Mako is pretty close as well. They are only 2yrs apart ans have a very close setup.

There were no knee's per say installed in my boat, but the raising of the stringer height did the same thing as far as strength and may be  a bit stronger.

http://www.classicmako.com/projects/xshark/bw3.htm

http://www.classicmako.com/projects/xshark/bw30.htm

http://www.classicmako.com/projects/xshark/bw31.htm

This not only gave a lot of strength to the transom, but allowed a lot more support for the deck being extended over where the splashwell use to be.

You can't see the top mounting holes for the bracket in the pix's. There is a piece of 4in "U" channel alum that goes all the way across the inside of the transom. It is aprox 6in on center higher than the floor level.

[JimCt]

warthog5,

Great pictures & narrative!  Seeing the step-by-step documentation of your work lays out clearly how I can re-core my transom, if need be.  Since the 170 has decking all the way aft to the transom, the job will be simpler but the basic steps are the same.

[warthog5]

I would presume that you would glass everything to every stringer, hull side, anything to get more support. AND multiple layers, each being scruffed/ground and the next being longer than the previous.

 Multiple layers, each being scruffed/ground is not the way to do it.

Work cleanly, have all your glass precut and sized and start laying. While the previous layer is still green lay the next one and so on.

Note that a 2nd helper is a BIG plus and that working in the middle of the summer doing a transom will test you. Cooler weather make's thing's easier. this is due to shorter pot life in the summer.

[Mako254]

[Mako254]

I guess it works...

to inbed pictures go to this link and upload you photos.
below each one you will find three http,  html links copy and paste the third link into your text and the photo should be inbeded.

Thanks to all who showed me this.