Reply
 
Thread Tools Search this Thread
 
Old 07 April 2009, 13:54   #1
Member
 
Country: UK - England
Town: North East
Boat name: Sarah Louise
Make: Honwave T38IE
Length: 3m +
Engine: 15 Yamaha, 8 Mariner
Join Date: Jul 2008
Posts: 226
Long Shaft Vs Short

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
__________________

__________________
Fishery Pokery is offline   Reply With Quote
Old 07 April 2009, 14:52   #2
Member
 
m chappelow's Avatar
 
Country: UK - England
Town: yorkshire
Boat name: little vicky
Make: avon ex RNLI
Length: 3m +
Engine: tohatsu
Join Date: Mar 2008
Posts: 2,310
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 ,
__________________

__________________
m chappelow is offline   Reply With Quote
Old 07 April 2009, 16:40   #3
Member
 
Country: UK - England
Town: Looe
Make: Delta
Length: 4m +
Engine: Mercury
Join Date: Apr 2004
Posts: 1,335
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!.
__________________
Turbodiesel is offline   Reply With Quote
Old 07 April 2009, 18:33   #4
Member
 
Bigmuz7's Avatar
 
Country: UK - Scotland
Town: Glasgow
Boat name: stramash
Make: Tornado
Length: 5m +
Engine: Etec 90
Join Date: Feb 2006
Posts: 5,068
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
__________________
Bigmuz7 is offline   Reply With Quote
Old 09 April 2009, 12:01   #5
Member
 
Country: UK - England
Town: North East
Boat name: Sarah Louise
Make: Honwave T38IE
Length: 3m +
Engine: 15 Yamaha, 8 Mariner
Join Date: Jul 2008
Posts: 226
Thanks for the advise guys, I think I will avoid this route then.
Cheers again,
Geoff
__________________
Fishery Pokery is offline   Reply With Quote
Old 10 April 2009, 12:05   #6
Member
 
Country: USA
Town: Oakland CA
Length: 3m +
Join Date: Feb 2005
Posts: 6,653
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
__________________
jyasaki is offline   Reply With Quote
Old 10 April 2009, 17:27   #7
Member
 
Country: Netherlands
Town: Holland
Make: Brig F360S
Length: 3m +
Engine: Yamaha 70hp
Join Date: Jan 2008
Posts: 85
Quote:
Originally Posted by Bigmuz7 View Post
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)
__________________
reinier is offline   Reply With Quote
Old 10 April 2009, 18:12   #8
RIBnet admin team
 
Nos4r2's Avatar
 
Country: UK - England
Town: The wilds of Wiltshire
Boat name: WhiteNoise/Dominator
Make: Ballistic 7.8/SR5.4
Length: 7m +
Engine: Opti 225/Yam 85
MMSI: 235090687/235055163
Join Date: Jul 2005
Posts: 12,645
RIBase
Quote:
Originally Posted by reinier View Post
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.
__________________
Need spares,consoles,consumables,hire,training or even a new boat?

Please click HERE and HERE and support our Trade Members.

Join up as a Trade member or Supporter HERE
Nos4r2 is offline   Reply With Quote
Old 11 April 2009, 11:54   #9
Member
 
Bigmuz7's Avatar
 
Country: UK - Scotland
Town: Glasgow
Boat name: stramash
Make: Tornado
Length: 5m +
Engine: Etec 90
Join Date: Feb 2006
Posts: 5,068
Quote:
Originally Posted by reinier View Post
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
__________________
Bigmuz7 is offline   Reply With Quote
Old 11 April 2009, 13:03   #10
Member
 
m chappelow's Avatar
 
Country: UK - England
Town: yorkshire
Boat name: little vicky
Make: avon ex RNLI
Length: 3m +
Engine: tohatsu
Join Date: Mar 2008
Posts: 2,310
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
__________________

__________________
m chappelow is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -5. The time now is 23:54.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.