Long Shaft motor on 15" Transom

Joined
Nov 3, 2008
Messages
27
I have a Tohatsu 9.9 with a 20" shaft mounted on my 13' Atlantic Skiff with a 15" transom. WOT is less than 8mph and it will not plane out. Would raising the engine help? If so how would you suggest?
 

BonairII

Commander
Joined
Jun 7, 2011
Messages
2,727
Re: Long Shaft motor on 15" Transom

I have a Tohatsu 9.9 with a 20" shaft mounted on my 13' Atlantic Skiff with a 15" transom. WOT is less than 8mph and it will not plane out. Would raising the engine help? If so how would you suggest?

A long leg on a short transom will def hurt performance. You would probably need an adjustable jackplate to raise the motor. I don't know how much you can safely "jack up" an outboard, though.
 

cyclops2

Banned
Joined
Apr 19, 2011
Messages
1,237
Re: Long Shaft motor on 15" Transom

Is the boat Aluminum or plastic ?
V or something else ?
How heavy are you, your body weight ?
Correct prop ?
How many pounds of battery / trolling motor / anchor / down rigger weights ?
Do you know the bare boat weight ?

Can you post a picture of boat ?

My Aluminum 16' ...15" transom, with a loaded hull & 9.9 Evinrude is almost able to plane.
 

skibrain

Senior Chief Petty Officer
Joined
Jun 17, 2004
Messages
766
Re: Long Shaft motor on 15" Transom

Best to trade for a short shaft motor. Motor is running 5" deeper than is correct. Lots of extra drag and additional draft that you don't need.
 

cyclops2

Banned
Joined
Apr 19, 2011
Messages
1,237
Re: Long Shaft motor on 15" Transom

I have put my 9.9 on a 15" transom 12' long Aluminum boat.............SCARRY quick on acceleration & turns MUST be at reduced planing speeds. I almost rolled the little boat feeling it out.
 

cyclops2

Banned
Joined
Apr 19, 2011
Messages
1,237
Re: Long Shaft motor on 15" Transom

A lot of older 9.9 hp always were able to be converted to either length with a few parts. A Jack Plate might do you just fine & be simpler & cheaper.
 

Home Cookin'

Fleet Admiral
Joined
May 26, 2009
Messages
9,715
Re: Long Shaft motor on 15" Transom

replace the motor rather than altering the boat. 9.9's are everywhere and just like they are easy to buy, they are easy to sell.
 

kfa4303

Banned
Joined
Sep 17, 2010
Messages
6,094
Re: Long Shaft motor on 15" Transom

Ideally you'd like the cavitation plate found just above the prop to be lever, or slightly higher than the keel of the boat. A jack plate like the one in jigngrub's link may be your quickest, cheapest answer, or you could just get a new motor per the previous posts. I think I may steal that one for myself:)
 

roscoe

Supreme Mariner
Joined
Oct 30, 2002
Messages
21,657
Re: Long Shaft motor on 15" Transom

I've run long shafts on short transoms before, and the performance was not that far off.

We really need to know more about your boat, as requested above.

"atlantic skiff" really means nothing to most of us, heck, it only shows up as a hand made rowwing boat on google.

width, weight, hull design, photos, prop pitch ????
 
Joined
Nov 3, 2008
Messages
27
Re: Long Shaft motor on 15" Transom

I have a junker Tohatsu 9.9 short shaft but the foot and housing is damaged. If I could locate a 15" housing the shaft is usable. Thanks for all the response.
 
Joined
Nov 3, 2008
Messages
27
Re: Long Shaft motor on 15" Transom

New to this forum and having trouble uploading picture of my Atlantic Skiff.
 
Top