Raised my motor, but questions...

[Bushwacker]

Yes, the extra blade alone on a 4B will add extra stern lift, although blade rake and how it's cupped also affect stern lift. If your Vortex is a 4B version, you might get more than 200 rpm/inch of pitch with it. The Vortex is an excellent prop; it's comparable SS version is the Apollo, which would probably slightly larger in diameter for the same pitch.

[erebus]

Originally Posted by Bushwacker

If your Vortex is a 4B version...

It was just a regular 3 blade.
Have yet to try a four blade. Getting there tho!

[erebus]

Had a quick run around Cape Cod Bay yesterday with a brand new 4 blade Quicksilver Nemesis 4 blade 12.8" (they call it 13")x17p prop.

Right off the bat she seems to want to plane off faster.
Not sure if the bow rises more initially before the stern comes up but that's what I thought first time up on plane. Just an observation, maybe I imagined it.
Planes good and at a much lower rpm/speed. Can hold plane till about 13 knots on smooth seas at about 3200 RPMS.
Max full throttle was 5000 RPM's on the nose and 31 knots via GPS.
Can cruise happily at 18-20 knots at about 3600 RPM's.
4 blader also grips good in a tight turn, alleviating some of the sliding sensation from moving the motor up two holes I noticed with the old three blade.

So now the question is do I change pitch, or is that pretty good?
I ordered a 4 blade nemesis 13x19p I can try too, but Ill have to pay for it. Or I just run the 17 and call it good. If I go 19 that will lower my RPMS by about 400, correct?
Maybe I should try a 15P?
115 merc likes 4750-5250. So the 17p is smack dab in the middle.
They don't make a 16 which would probably let me get the full 5250.

17P is probably good enough for my needs...

[Bushwacker]

All the performance changes you've reported are exactly what I would expect from a good 4B prop. Being able to plane at 13 kts indicates boat is fairly well balanced. If the load you were carrying was about what you normally carry, I'd say you've found the right prop. If you normally run heavier, a 16 pitch prop would allow motor to rev a little higher. If it's an aluminum prop, a good shop could probably repitch it.

FYI, as I've posted on here before, if I were running an inboard or a 4-stroke outboard, the first thing I'd do would be add a gage to measure intake manifold vacuum. If you observe a minimum vacuum of 5-7" at cruise, your exhaust valves will live a lot longer! (The exhaust valve is the hottest and typically most life limiting part in any 4-stroke engine.) Basic requirement is for prop to reach max recommended rpm at WOT with normal load and still be within recommended range at max load, but beyond that, I think I'd be inclined to pick whatever prop gave me the max speed at about 7" vacuum, provided that min planing speed was acceptable and it didn't ventilate in hard turns!