shrt shaft to long shaft conversion?

Tannoy · 23-06-2013 01:44PM #1

Hi all

I suppose I'm wondering if anyone knows weather its possible to somehow use a short shaft outboard motor on a boat that is designed for a long shaft? My boat is a fairline 19ft and the motor is a 20hp Mariner 2 stroke. At the moment the motor pushes the boat along nicely in calm water but looses performance in choppy conditions. I may have to consider trading it for long shaft but if anyone has ever lowered their motor using a bracket or actually converted it please let me know how you got on.

Thanks.

fergal.b · 23-06-2013 02:15PM

Hi Tannoy, your best bet would be to get a long shaft, you can get a jackplate but they are not cheep :eek: the other option would be to cut down the transom but with this you could end up with water coming into the boat when you throttle back or get hit by a wave. As your boat is designed for a long shaft and you hang a short of the back on a bracket your engine might end up being dunked in the water:eek:
Also if you ever go to sell the boat it would be better to have it as a longshaft with no extra holes drilled in

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Talent · 23-06-2013 04:42PM

Other possibility might be to pick up a junked long shaft of similar make and model where the motor is banjaxed but the drive is good. Might then be simpler to transfer your working top end to it. Did this easily once with a 4 HP Evinrude but a 20 HP job might be more formidable.

fergal.b · 23-06-2013 08:23PM

Talent wrote: »

Other possibility might be to pick up a junked long shaft of similar make and model where the motor is banjaxed but the drive is good. Might then be simpler to transfer your working top end to it. Did this easily once with a 4 HP Evinrude but a 20 HP job might be more formidable.

Good thinking Talent, I think the 20 hp mercury gearbox should also fit the mariner. You can also get a kit that lets you use your own gearbox you have to change the shaft and lengthen the water tube then put it back together with a spacer that looks like this. These kits are not that cheep and a bit of work to fit but it's another option

Tannoy · 24-06-2013 11:36AM

Great advice, thanks guys

davlacey · 24-06-2013 07:01PM

whats the measurement for the longshafts from the bracket to the prop? ive just measured my transome and its 20 inches from the top to the bottom i could be in the same position that a longshaft is a bit short

fergal.b · 24-06-2013 07:08PM

Short shaft is 15" long 20" and extra long is 25"

davlacey · 24-06-2013 07:19PM

yea mine is bang on 20" from top to bottom cheers

moonshadow · 24-06-2013 11:09PM

We recently did the opposite from long to short, had Killen marine do the job cost the guts of 600 e including a full service. Excellent service and result.

fergal.b · 27-06-2013 07:20AM

This could be worth a look http://www.adverts.ie/boats-accessories/mariner-yamaha-omc-20-30-40hp-gearbox-2-stroke-engine-2000-cork/3322113

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shrt shaft to long shaft conversion?

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