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Old 01 July 2007, 09:09   #51
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Mark what shaft length is the Honda? (sorry if this has been asked b4)

Chris
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Old 01 July 2007, 10:29   #52
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Originally Posted by mhb100 View Post
Hi Guys

thanks for the info about by zodiac transom issue. Looks like the trim/tile and engine height is ok so its a case that its poor design,etc

Like the idea of a transom plate - has any one done this?

currently the engine sits on a plywood pad. I assume I would remove this and fit over the plate or just discard it completely?

do you know where I can get them made up at a reasonable cost?

and how do you fix/seal these to the transom; apart from the 4 engine bolts?

any information appreciated as i need to get this ordered asap

thanks
Mark
Hi

I would lift the engine off clean out the cracks and fill with gelcoat and make a new spacer out of marine ply(sealed with gelcoat) or plastic to clear the lip at the top of the transom then have a stainless steel plate folded up to go over the transom like an upside down U section then bolt the engine back on.
If you make a patern out of carboard for the outside and the inside of the transom with top edge as a datum line you can mark the holes for mounting the out board(if you have 12 mm bolts i'd have 16 mm holes put in so that you can easily mount the outboard and get plenty of sikaflex in). take these to a metal fab shop and get them to make it up, you'll have to tell them the back to front dimension of the transom so they can bend the U section to fit +1 mm on the inside dimension like the pictures i posted here

http://rib.net/forum/showthread.php?t=20173&page=3

But thats just what i'd do

James
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Old 01 July 2007, 13:20   #53
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Mark what shaft length is the Honda? (sorry if this has been asked b4)

Chris
Hi Chirs


Long shaft,
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Old 01 July 2007, 13:22   #54
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Hi

I would lift the engine off clean out the cracks and fill with gelcoat and make a new spacer out of marine ply(sealed with gelcoat) or plastic to clear the lip at the top of the transom then have a stainless steel plate folded up to go over the transom like an upside down U section then bolt the engine back on.
If you make a patern out of carboard for the outside and the inside of the transom with top edge as a datum line you can mark the holes for mounting the out board(if you have 12 mm bolts i'd have 16 mm holes put in so that you can easily mount the outboard and get plenty of sikaflex in). take these to a metal fab shop and get them to make it up, you'll have to tell them the back to front dimension of the transom so they can bend the U section to fit +1 mm on the inside dimension like the pictures i posted here

http://rib.net/forum/showthread.php?t=20173&page=3

But thats just what i'd do

James

Hi James, thanks for this, very helpful
Mark
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Old 01 July 2007, 16:59   #55
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SO therein lies the problem your transom height (21") is designed to take a short shaft and the guys that rigged the boat clearly had a longshaft in stock so made it fit by fitting it too high on the transom.

Thats a bit shite really.

Sorry if this has already been covered.

Chris
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Old 01 July 2007, 17:02   #56
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Crisis might be over- transom not failing................

Guys,

Looks like the issue with the zodiac transom might not be what it appears.

First of all i'm gonna to put the issue of engine position on the transom to bed

......The zodiac has a lowish transom and the honda (long) is also longer than most at 537mm; compared to say a Suzuki 4 stroke which i now know to be 508mm. The saddle cannot sit on the transom without putting the cavitational plate several inches below the hull. I guess in 1999 there were not many 4 strokes to choose from!. I have dropped the engine 1 bolt hole so its just inline with the hull as opposed to 1" above as it might assist with the cavitation i get when turning. Having spoken to many dealers and mechanical engineers whilst it is more common for engine saddles to sit on the transom there is no reason for it to as the 4 engine bolts are more than adequate to take the load and distrube it. The bottom line is that most do sit on the top of the transom; or very near to it because the engine length dictates it.. moral seems to be choose the ideal engine length for your transom then you'll get the best of both worlds so a 508mm seems best for the Zodiac Pro Open

The failing transom....Good news.

After investigation today I now know there is no damage to the structural part of the transom. The spliting is not on the main transom but where the top and hull moulds join together. The split runs parallel to this seam - there is no splitting elsewhere, and having moved the engine today and checked all bolt holes,etc im pretty sure of that.

Having done a postmortum on the cracks (with a grinder) its clear to see whats gone on. On top of the solid transom (where the lip is) is actually a hollow box section (yes hollow,what a design!) the top is about 3-4mm thick the rear about 20mm and the front (where the cracks appeared) about 5mm. In between all this is a hollow core section running the length of the transom. The join where the cracks appeared seem to have the least silkaflex or similar bonding the join. Remedy seems to be to fill with epoxy and finish in gel coat. If the crack had been anywhere else then the outcome would have been very different! . I will look at a transom plate as well.

only remaining issue is the weight of the engine exceeding the transom weight. Still working on this. If the insurance dont have an issue then ill keep it; if not its engine exchange time......

M
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Old 01 July 2007, 17:05   #57
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PS forgot to say thanks Nos for your help - really appreciated mate
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Old 01 July 2007, 17:54   #58
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Old 01 July 2007, 23:07   #59
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Fascinating thread...

I'd always thought a longshaft was a longshaft was a longshaft but 537mm vs. 508mm is more than an inch difference. What the boat manufacturers should do is have an integrated transom height extension system where you can add in a factory designed integrated extension piece for the particular outboard you opt for so that the saddle of the bracket can sit directly on the transom.

It would seem to me that having the bracket saddle resting directly on the transom along with 4 bolts, will disperse stress alot more effectively than 4 bolts only would.
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Old 02 July 2007, 07:40   #60
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Hi,

I think the zodiac pro open (in my year) may be the exception to the rule about 4 bolts versus resting ontop of transom.

The bottom line is that the top part of the transom is a hollow box section. So in this design the solid transom part is where the 4 bolts are. I'm not sure on this model I would want the shoulder taking the weight!

Zodiac did beef the transom up since 1999; whilst I dont know what mods they have done, they have increased the transom max by about 30kg. I can't even seem to find out if the transom top was supposed to be solid ( and therefore a fault in production) or not in the first place. It just seems rather a strange design.

Good news is that is that its worked fine for 8 years and theres lots of these rib/honda packages out there......

M
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