Prop Question
 

I know what you are thinking.....oh no another prop size discussion !!

Not the case here. My SC came with a brand new, spare prop. It clearly states it is 15 1/4 x 15. (Part Number 48-78116 A45.)
All my cross reference research indicates the current size is 15 1/2 x 15.
(new part number QA 2008X)
Is the 1/4" a big deal ?? By the way I have twin 165 Mercs....

Thanks.

I think you're under-rating the value of a good prop discussion. ;) In my humble opinion, other than preventative maintenance, proper propping is the most important thing you can do to get the best out of your boat.

The QX2008 is a Quicksilver model. Although they are the same basic geometry as the shown Black Max, I think mixing them is a suspect idea for regular use, as the shape, cup and rake might vary enough to cause subtle problems. However, I don't think it would present an issue as a spare/emergency prop.

I suspect that the diameter difference is a result of the need to lift heavier outboards (read 4-strokes) and the evolution ofthe Merc alloys which may allow for a thinner blade and maybe in turn a greater diameter. Again this is probably due to weight and cg shifts as motors have evolved. For example a modern 4.3L will have more power than any old inline six, but the weight is farther aft, so it will require more lift. And it shouldn't have any problem moving a bit more water. Merc/QS has probably assessed that and changed their molds with the times.

If you are currently using the 15-1/4" props, and go with the new version, just make sure your zinc torque/trim tab does not impede the props rotation.They make a cutaway zinc for some apps...

These are just my general observations. Some of the engineers and guys with a lot of rigging experience can probably offer a better perspective.