Long Shaft Vs Short

[Fishery Pokery]

Hi everyone,
If I was to use a longshaft aux on a short shaft transom, what would be the ill effects?
Thanks for any help.
Cheers,
Geoff

[m chappelow]

not a lot ,though with some engines you may find it doesent start well owing to more back pressure on the exhaust ,just had a similar thread in the inflatable section ,

[Turbodiesel]

Dont think you will have problems with the exhaust as the exhaust will be in the same place as it would on the short shaft engine. You will have performance problems, as the leg will be 5" deeper in the water. You will also get alot of spray running up the leg and possibly getting into the powerhead (dependent on your speed of course) You could even have spray coming back into the boat Speed dependent again!.

[Bigmuz7]

For sure .. extra drag .. less top speed.. more spray.. worse fuel economy.. plus you cant go into shallower areas without lifting But youd need to be a bean counter to really notice it

[Fishery Pokery]

Thanks for the advise guys, I think I will avoid this route then.
Cheers again,
Geoff

[jyasaki]

You're talking about an aux motor. You're probably not going to have stellar performance anyway. I would doubt that spray is going to be an issue, unless you're talking about a 25hp kicker.

jky

[reinier]

Originally Posted by Bigmuz7

For sure .. extra drag .. less top speed.. more spray.. worse fuel economy.. plus you cant go into shallower areas without lifting But youd need to be a bean counter to really notice it

That's BS, every inch the deeper or less deeper an engine is in the water is really good noticable.

Using a longshaft on a shortshaft transom will cause:
- much less topseed
- excessive spray that could get in the boat
- heavier steering and more stress on the steering-system
- acceleration problems
- way more stress on the transom due to the longer shaft (moment of power changes)

[Nos4r2]

Originally Posted by reinier

That's BS, every inch the deeper or less deeper an engine is in the water is really good noticable.

Using a longshaft on a shortshaft transom will cause:
- much less topseed
- excessive spray that could get in the boat
- heavier steering and more stress on the steering-system
- acceleration problems
- way more stress on the transom due to the longer shaft (moment of power changes)

It's an auxiliary. You could put a 30" shaft (if such a thing existed)on a short shaft transom and it'll still create less stress on it than the main engine. It's unlikely to make over 5 knots anyway.

[Bigmuz7]

Originally Posted by reinier

That's BS

Ok .. so you are a bean counter .. but not a very good one ..since you actually agreed with some of the things I said

[m chappelow]

i have run long shafts on short transoms for years ,i dont think you will have any problems using one as an aux ,as i said earlier though some engines may not start as good if there is only a small exhaust bypass hole at the top of the leg ,regards the exhaust being in the same place it wont be ,if it comes out near the prop or through prop it will be 5 inches deeper in the water ,the extension bit is above the cav plate normally ,but you will get a buit more spray perhaps but not at displacement speeds that an aux will give you ,i cable tie a shaped piece of wood on one of my engine as there is a flatsection on the leg which cuts my spray down,regards mart

[reinier]

Originally Posted by Nos4r2

It's an auxiliary. You could put a 30" shaft (if such a thing existed)on a short shaft transom and it'll still create less stress on it than the main engine. It's unlikely to make over 5 knots anyway.

Ahhh, never mind, I haven't read that part!