Help with prop selection

Trying to get another prop with more pitch and lower the WOT rpm. Currently I have a stainless 17 pitch prop on a 2001 17 foot javelin with a johnson 115 (13 spline) same year model. Problem is I'm hitting 42 mph but having to keep the throttle at 5800rpm. At that rpm I still have throttle left so having to watch the rpm to be sure I'm not going over the max WOT rpm. Wondering if I went to a 19 pitch if it would lower the rpm to get it closer to the max rpm with the throttle at full advance. I'm looking to get an aluminum atleast for now just to be sure the rpm is in range before going all out on stainless and it being over pitched and not able to return.

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All depends on how much you have left after you stop at 5800. If you advance the throttle fully what is the rpm? If it's 5850 or 5900 then no, if it's 6K plus then yes go with a 19 itch of the same design. By your numbers you are running a decent prop as you are right at 10% slip. If you use a 19 and get the same slip you would be doing 47 at the same 5800rpm.
Remember your time to plane will likely be slower.

It will hit 6200 rpm if I go full advance. First time it happened the motor cut out as if I turned off the key then came back to life once the rpm went down. Scared the mess out if me. So now I try to watch the rpm closely.

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Rule of thumb is 200rpm per inch of pitch. So a 19 should bring you down to 5800 WOT and a 21 5400. So a 19 would be close to perfect.

Is there by chance anything I can hook up to verify my rpm? Be nice to know how accurate my tach is before trying to change the pitch.

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I just went through this. this cheapo tach worked fine for me. https://www.amazon.com/Maintenance-T...449227&sr=8-15

Note:This particular one won't work with a 4 cylinder 2 stroke.

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Originally Posted by huntersdad

Is there by chance anything I can hook up to verify my rpm? Be nice to know how accurate my tach is before trying to change the pitch.

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This one will do all 2 strokes: https://www.amazon.com/Timorn-Replac...2s9dHJ1ZQ&th=1

For some reason neither link is working for me.

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This it?Attachment 426180

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Yep, all you need is a 2nd tach to compare. If you know someone at a shop see if they would let you borrow a shop tach. That would be best checker.