Teak is renowned specifically because it does NOT tend to rot, warp or swell a lot in moisture-laden situations. Pine.... is not teak. In wide boards, it is especially prone to cupping, warping, and rotting. Wrapping it in fiberglass forestalls this, but is a lot of work. For your application and abilities, sticking with aluminum would seem to make the most sense. You can trim it to be moderately hydrodynamic, you won't have to ballast it to make it sink (half inch is pretty hefty) it's compatible with the rest of the steering system you've already (re)built, and you know how to work it. K.I.S.S.
** please note that original poster is experienced metalworker who has already redone tiller in aluminum.
Last edited by paulk; 11-28-2009 at 10:32 PM.