reduce avon transom

[cwoakes]

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!

[Rogue Wave]

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.

[cwoakes]

Originally Posted by Rogue Wave

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.

[Rogue Wave]

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

[cwoakes]

Originally Posted by Rogue Wave

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.

[jyasaki]

Originally Posted by cwoakes

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

[Landlockedpirate]

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.

[cwoakes]

Originally Posted by Landlockedpirate

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.

[Downhilldai]

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.

[Landlockedpirate]

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.

[cwoakes]

Originally Posted by Landlockedpirate

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.

Spoke with a lot of people in the business and decided to go ahead and take off 3 inches. Came out fantastic! Still plenty of transom for safety and the motor sits right where it should in the water. Nothing left but to apply some solar seal (rubber caulk) hear and there. Need fiberglass and rubber black paint to dry completely. Even in rough seas I will be fine now. 20140623_144000.jpg20140623_143811.jpg20140623_143800.jpg

[Doug_G]

Originally Posted by cwoakes

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!

Sell the short shaft and buy a long shaft. I think they are like 15" and 20" i.e. 5" difference.

The line of the base of the transom should roughly line up with the cavitation plate.

This way you have a good engine and a perfect transom. A cut down transom would devalue the RIB significantly when you want to sell it, plus lowering the freeboard is not a good idea.

Oops, Now realise that you have already cut it. Good luck with it.

[Landlockedpirate]

Originally Posted by Doug_G

Sell the short shaft and buy a long shaft. I think they are like 15" and 20" i.e. 5" difference.

The line of the base of the transom should roughly line up with the cavitation plate.

This way you have a good engine and a perfect transom. A cut down transom would devalue the RIB significantly when you want to sell it, plus lowering the freeboard is not a good idea.

Good advice, but it looks like he has already got the jigsaw out

At least it looks like a neat job.

[cwoakes]

Originally Posted by Doug_G

Sell the short shaft and buy a long shaft. I think they are like 15" and 20" i.e. 5" difference.

The line of the base of the transom should roughly line up with the cavitation plate.

This way you have a good engine and a perfect transom. A cut down transom would devalue the RIB significantly when you want to sell it, plus lowering the freeboard is not a good idea.

Oops, Now realise that you have already cut it. Good luck with it.

I hear what your saying, The value is irrelevant, I paid $600.00 for the boat. As for the freeboard it was reduced minimally, and lets remember it is an inflatable. Years ago I got caught in a hellacious storm and fearing the boat would just flip over in the high winds and waves , I sat in the bottom, kept the motor running and pulled the plug filling the boat half full of seawater. I easily bobbed up and down dragging my anchor line and never feared of sinking. I love Avons and the fact they are indistructible.( the older ones, do not know much about the newer ones). I appreciate your insights, in a perfect world I would own a long shaft, but it is what it is. Had I hacked off 7-8 inches of the transom, I would be worried, thre inches is not a deal breaker. Beats the hell out of a 600.00 extension on the motor or a half-ass jack plate rig. Happy boating, lobster season is just around the corner!!!!!!!
BTW this is a photo of my vintage Avon I have been using for at least 10 years, just can't kill em! lol

[cwoakes]

Took it out on a test run for the first time. Popped right up on a plane even though it is underpowered, tried to flood the transom, couldn't do it, still has 17 inches of freeboard! Handles fantastic, Scallop season in a few weeks and then lobster season in August. Perfect timing!