Adi,
One way to look at this is to work away from what you might have done if it was brushed motors, etc.
Not familiar with the commodore (pause to have a look) OK, nice little cabin cruiser
What do you want it to do? cruise, plane or terrify the locals and impress Stavros?
For fair performance - good planing and appearance a pair of S400s would do a good job if they were modestly propped - around 30 mm max and they would run on 6, 7 or 8 cells buggy pack (S400 7.2V have a kv of 2300 from memory)
I run my pt boat on a single prop - 35mm 2-blade and either a S600 7.2 eco or a single brushless "bell motor" with 10A ESC which gives the same performance with vastly less weight
SO: I would suggest a pair of fairly small brushelesses with KV around 1500 to 2000, props which would suit S400s (25 to 30mm dia) and 2 cheap aero ESCs, or you might try one ESC if you like a challenge
By small I am thinking of something with numbers like 2215-10 or similar - appearance like
http://www.giantcod.co.uk/epower-2215-1700kv-brushless-outrunner-motor-p-403200.html?osCsid=8auev3nv3no6085tiike3385v7and the price looks reasonable , too
Please tell us how you think, and what you do - and show us the pics
andrew