Yes the SHO requires a "minimum" of 89 P.O.N.

P.O.N. = "pump octane number" and is the average of the Research Octane Number (octane determined on an unloaded engine) and Motor Octane Number (octane number determined on a fully loaded engine)

Hence the formula (R+M)/2 = P.O.N.

I don't think any pumps in Texas designate their octane ratings any other way but check at the pump to be sure.

Personally, at this level of investment, I plan to use premium (91-93) to ensure that there is no pre ignition. I also don't trust that the 89 octane is exactly 89 and if it isn't, you are below the requirements of the engine.

It would be interesting to know if four strokes in general are more sensitive to octane ratings than two strokes or is it just a matter of compression ratios.

It's tough waiting for a boat! (I am also)... You think about octane ratings, hitch balls, and other diversions...