Prop Question

[Dogcrew]

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.

[McGillicuddy]

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.