Shortening an XL shaft to L shaft?

Balthazar · 22 June 2021, 14:31

Hi all,

Do anyone have experience with shortening an XL shaft toward a L one?

I have a Humber 6.5m and it seems to be a standard L transom, but my engine is a Honda BF150 XL shaft. I have raised the outboard with a jack plate but not sure if this is the best way to go. It seems that my outboard is still a couple of inches too low (the water intake grid is about 2 inch below the hull) and by raising the outboard that weight 265kg I may put too much pressure on the transom.

Did anyone already modified the outboard’s size and would this be as a cost or job difficulty? Cheers

jonp · 23 June 2021, 00:20

Mentioned it once to a mechanic who told me its to costly and to swap motors is the cheapest option.

Jon Tallis · 23 June 2021, 14:54

Anti-ventilation plate 2" below the Hull is way-wrong and I'm kinda with you on the extra load/leverage with the jack plate.

Changing the leg and lower unit so make the XL into an L isn't mechanically complex but unless you can source used parts then a good used engine (if you can find one in Covid-world) would be way cheaper as you can then sell the XL.

Options I'd be considering would be.
1- Find a used Long shaft motor the same model as yours with a blown power-head and swap your power-head onto it. (if you can find one)
2- Re-engine the boat with a good, used L shaft (V. Hard to find right now)
3- Get a reputable boat builder to rebuild the transom to suit the XL. Can't stress the "reputable" bit enough! Check this first with your insurer as they may want a surveyor to oversee the work especially if the boat is RCD certified or MCA coded.
4- stick with the jack plate but keep a very very close eye on the transom for any cracking or flexing. If you spot anything at all, stop using the boat right away.

If it was mine and assuming I wasn't planning to re-engine it anyway, I'd probably go option 3

Nasher · 23 June 2021, 17:51

This is what I did rather than a jack plate to put an XL shaft DT200EFI on my RIB which had been cut down by a previous owner.

It lasted many years and some really rough weather trips out, so I've just refreshed it to take the 225 Opti I have ready to go on.

It spreads the load nicely across the transom.

The lower engine mount bolt holes have some bolts in loosely in the first image, just temporarily to keep the rain out.

Nasher.

Jon Tallis · 23 June 2021, 18:22

Yup, that'd work too. Nice job!

pagick · 23 June 2021, 23:59

Quote:

Originally Posted by Nasher

This is what I did rather than a jack plate to put an XL shaft DT200EFI on my RIB which had been cut down by a previous owner.

It lasted many years and some really rough weather trips out, so I've just refreshed it to take the 225 Opti I have ready to go on.

It spreads the load nicely across the transom.

The lower engine mount bolt holes have some bolts in loosely in the first image, just temporarily to keep the rain out.

Nasher.

I did the same metal load spreader on a sib many many years ago. My Avon Spitfire Sib had all wood transom factory cut to a height that was 2.5" too low. I fitted a wood block to match what I had to what I needed. Then with two 1/8" stainless sheets 4" wider on each side of filler piece, and a couple inches longer than bottom of motor and 9 stainless bolts plus the motor bolts sandwiched it all. Zero problems. But the motor was only 35HP from the 80's that weighed 120 lbs.

Nasher · 24 June 2021, 11:44

The Aluminium Plate by the way is 15mm thick.

I went with that thickness after discussing it with a local builder of large Aluminium Catamaran commercial fishing boats.
They use 15mm for the transoms of their boats and would happily put the largest of Outboards on it.

They also cut it for me all those years ago for next to nothing, and it cleaned up nicely for my refresh.
I did try to get a price out of them for a new one but they didn't want to know.

The other benefit of the XL shaft engine, on my RIB at least, is getting the powerhead up higher out of the water.
The RIB arrived with me fitted with a Long shaft 150VRO, and it was swamped by my wake every time I slowed down.

Nasher.

Balthazar · 24 June 2021, 19:33

Hi guys,

Thanks for your replies, appreciate your help. I like the idea of fitting the aluminium transom plate, a very good point. I was thinking about making a plywood plate with fiberglassing both sides, exactly the same way as on the pictures. Cheers!

Almatt · 24 June 2021, 22:17

Hi got the same engine and it measures 28 inches shaft length options xl , my transom is only 25 inches ? what did you take your transom too to get where you are now ?
Best , Al