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Old 23 June 2014, 07:47   #1
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Country: USA
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Boat name: Zelda 3
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reduce avon transom

I have a 1992 avon R4.00 supersport. i would like to cutdown the transom a few inches to use a brand new merc. 9.9 thumper short shaft. My question is: what is inside the transom? Do not want to start cutting if it is just stringers and foam with a glass layer. I am hoping it is solid wood. Any help greatly appreciated!
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Old 23 June 2014, 09:07   #2
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Not a good move at all

If you have to use the wrong size engine then put a jack plate on to lower the engine. But its still not right because the actual engine is closer to the water.
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Old 23 June 2014, 09:13   #3
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Quote:
Originally Posted by Rogue Wave View Post
Not a good move at all

If you have to use the wrong size engine then put a jack plate on to lower the engine. But its still not right because the actual engine is closer to the water.
I am only taking it down 3 inches. I have heard nothing good about jack plates. What are your concerns? this will still leave a 17 inch transom depth.
Appreciate your thoughts. BTW do you know if the transom is solid wood or stringers.
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Old 23 June 2014, 09:28   #4
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Okey Dokey

Marine ply inside a Grp Sheathing Use an Angle Grinder with a thin cutting Blade and eye , nose ear and hand protection

I truly hope 6 months down the line you realise I had given you don't regret doing it

Google Jack plates and see if it offers you an alternative
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Old 23 June 2014, 10:03   #5
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Quote:
Originally Posted by Rogue Wave View Post
Okey Dokey

Marine ply inside a Grp Sheathing Use an Angle Grinder with a thin cutting Blade and eye , nose ear and hand protection

I truly hope 6 months down the line you realise I had given you don't regret doing it

Google Jack plates and see if it offers you an alternative
I am hearing you, nothing is better than experience! Is there a jack plate brand you would recommend?? Seems like that might be the way to go as I can use the motor on both of my avons. They seem to be rather inexpensive compared to other alternatives. Performance is not an issue as a 9.9 isn't gonna push a 13.3 very fast anyway. I use the boat for recreational lobstering in the keys. Reliability is the key, not performance.
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Old 23 June 2014, 10:20   #6
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Originally Posted by cwoakes View Post
I have heard nothing good about jack plates.
What have you heard?

Pushing the engine back a bit effectively "lengthens" the hull, producing less bow rise at initial acceleration. Allows you to use the shorter shaft motor with less risk of a following sea or deceleration wake inundating the lowered transom. Frees up the area just ahead of the transom giving you more deck space (that would normally be reserved for the powerhead to tilt forward.)

You may need longer control cables/hoses and wiring - check that out before making the switch.

jky
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Old 23 June 2014, 10:31   #7
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Rogue Wave is right, cutting the transom is a bad idea.

But I can see why the OP thinks its a good idea. Its a 22 year old boat (Is it a rib or sib ?), worth a few hundread quid at most and the boat is plated for a much bigger engine than the OP is using. The small engine weight means that taking 3" of height out of the transom wont be an issue and as long as its well sealed it wont cause any delamination problems.

But why bother, a small Jack plate in the USA is only $100, and it will solve the problem in a neat and professional way. It can be removed when you sell the boat and the boats value is maintained.

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Old 23 June 2014, 10:37   #8
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Originally Posted by Landlockedpirate View Post
Rogue Wave is right, cutting the transom is a bad idea.

But I can see why the OP thinks its a good idea. Its a 22 year old boat (Is it a rib or sib ?), worth a few hundread quid at most and the boat is plated for a much bigger engine than the OP is using. The small engine weight means that taking 3" of height out of the transom wont be an issue and as long as its well sealed it wont cause any delamination problems.

But why bother, a mini Jack in the USA is only $100, and it will solve the problem in a neat and professional way. It can be removed when you sell the boat and the boats value is maintained.

New TH Marine Mini Jacker Small Outboard Jacking Jack Plate THM MJ1DP | eBay
I hear you, but LOWERING the motor on the transom means that the tiller and all controls will not clear the top of the transom. jack plates are usually installed when a long shaft is to be used on a short transom, not the other way around. Think about it, if I install the motor 3 inches down from the top of the transom the tiller and gas line and choke will all be obstructed by the top 3 inches of the transom.
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Old 23 June 2014, 11:31   #9
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Chop the motor in for a longshaft and leave your cutting gear in the shed.

BTW, early '90s Avon transoms were made of plywood & GRP - you won't find any foam in there.
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Old 23 June 2014, 11:39   #10
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Sorry, should have said, I mounted one upside down. I didnt realise you had a tiller engine, you may need to make some further modifications.
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