AWSA considers a boat to be modified if any of the following occur.
"New or Modified Towboat
A towboat model tested at the preceding year's towboat test will be considered "new or
modified" when any of the following conditions are met:
1. Non Propulsion System Related Items
(a) The towboat hull / plug has been changed or modified in any way from the
gunnel downward. This includes changes to spray rails, strakes, etc. This also
includes a change in the size or location of the stability fins or shaft location.
(b) A change is made from a closed deck to an open bow, or vice versa.
(c) There is a change in engine placement or location.
(d) A change in speed control software or hardware that impacts the skiers’ pull in
slalom, trick or jump.
(e) There is a change in total weight of more than 10%.
(f) Any other changes must be approved by the AWSA Towboat Committee prior to
the boat tests.
2. Propulsion System Related Items
(a) There is a change in the engine manufacturer or model as tested from the
previous year. This includes cubic inch displacement, horsepower,
carburetion/EFI, engine management system (ECM), etc.
(b) There is a change in transmission gearing (e.g., 1:1, 1.25:1, 1.5:1, etc.).
(c) There is a change in propeller size, blade number or material (I.e.: bronze to
This came from the 2012-2013 AWSA Tow Boat Policy Manual