Transom extension

[BobA]

Could any of you knowledgeable people advise me as to the best method of extending the transom on my Yam inflatable so that I can fit a long shaft outboard. I need the longshaft for the boat but do not want to be humping two variants of outboard around so thought that it would be easier to make the transom higher.
Bob

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[tcm]

erm, why d'ya need to extend the transom? A longshaft will simply sit deeper in the water - what's the problem? Normal o/bs are shorter shaft hence cheaper, but a longshaft wd sit deeper, in the water, but no prob with that. Am I missing something?

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[BobA]

Probably not, but that "nice man in the shop" suggested that I would need to extend it for the motor to push properly.

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[Talbot]

certainly will not be quite so efficient, and will act as an egg whisk on the bottom at greater depths, but not a great problem, - try it

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[tcm]

well, yes, but then powerboats go to great effort to get the drive further down in the water.

If you really do want to extend the transom, I wd use marine ply of the same thickness as the transom (ie quite thick , minimum 3/4inch better 1inch) , sand down and then especially put a radius on the upper edge for easy handling on the thing and attach as large a piece as poss on the inside (check the engine clears the existing transom tho) of the transom with drilling 6 holes three top three lower 10mm dia then using A4 10mm (17mm head) set screws (bolts) with nyloc nuts (with the blue bits) and oversized washers and dobs of silicon mastic in the hole and around the areas where the new piece mates with the transom) before tightening. The new piece will have to make room for any drain bung hole, of course.

But i wd try hard to use the transom and longshaft as it is first

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[dralex]

I think there's a theoretical increase in risk of flipping the inflatable with a long shaft. I susepct that would only happen if the OB was too powerful for the dinghy and if you were sitting on the transom and then wellied it from idle to full throttle whilst going up the face of a wave!!

Just a thought.

<hr width=100% size=1>Life's too short- do it now./forums/images/icons/wink.gif

 

[dickh]

You shouldn't need to extend the transom, my friend uses a longshaft Honda 2HP on both his hard dinghy & inflateable. It was inherited from a previous boat where it was intended as an emergency backup engine - but never actually used in anger.
It was too expensive to convert back to a short shaft model.
If you make the transom higher, it won't go in it's bag when packed away
Try it first a see how you get on.!

<hr width=100% size=1>dickh
I'd rather be sailing... /forums/images/icons/smile.gif

 

[Rick]

Interesting problem - I'd be inclined to go with the "use it as it is" school, howeber that will cause a bit of an issue with going to a beach or ramp - that extra 6 inches or so draft might be a bother close to shore.

Extending the transom "up" in itself is going to put an awful torquing load on the transom attachment points - mind you using it at standard height will also as a function of prop being further down ... silly me.

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