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.

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Originally Posted by huntersdad

This it?Attachment 426180

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Might be, just read the fine print to make sure it's compatible with your motor. The one I bought doesn't do 4 cylinder 2 cycle.

I purchased last night, hopefully it will work. Should deliver tomorrow.

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Tiny tach is what most use. What prop are your running exactly? I 'd think you'd need a 20 pitch Raker for your setup.

Not sure on the diameter from memory but it's a 17 pitch. I'm hitting 42 mph, not sure what the max rpm would be if I went full advance, it did cut out around 6000 one time before I realized it. I just keep an eye on the rpm and try to keep it around 5700 to 5800. I'd like the raker but hate to buy if it ends up being too much pitch and can't return. Are there any places that let you try before you buy with props?

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I decided to look at the fine print of the tach I purchased, seems that it will not do a 2 stroke v4 so will be returning once it delivers. I have looked at several others and none I have found specifies it will work on a v4 engine. Does anyone know of one that will work? I will get the tiny tach if it works. I just haven't seen where it states it will work on mine.

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Originally Posted by huntersdad

I decided to look at the fine print of the tach I purchased, seems that it will not do a 2 stroke v4 so will be returning once it delivers. I have looked at several others and none I have found specifies it will work on a v4 engine. Does anyone know of one that will work? I will get the tiny tach if it works. I just haven't seen where it states it will work on mine.

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I bet it works. The tach doesn't care how many cylinders you have. It is based on the pulse from the stator. Here is the description from that link:

Description:

Inductive Hour Meter was powered by the built in changeable battery.
Easy to Install the digital memory tachometer.
Large LCD display for easy reading.
Waterproof Inductive Hour Meter Suitable for all 2 Stroke & 4 Stroke gasoline engines
Tachometer and Engine Hour Meter show both engine RPM and hours of operation

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Originally Posted by MDCrappie

I bet it works. The tach doesn't care how many cylinders you have. It is based on the pulse from the stator. Here is the description from that link:

Description:

Inductive Hour Meter was powered by the built in changeable battery.
Easy to Install the digital memory tachometer.
Large LCD display for easy reading.
Waterproof Inductive Hour Meter Suitable for all 2 Stroke & 4 Stroke gasoline engines
Tachometer and Engine Hour Meter show both engine RPM and hours of operation

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This is the part I read, which led me to think it may not work.. only way to know is to hook it up

Waterproof universal hour meter suitable for all two stroke (single/twin/3/6 cylinders) & four stroke (single/twin/3/4/5/6/8/12 cylinders)

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Just tested this tachometer, I put the tachometer setting to fire every revolution. And was getting around 3600 RPM at idle. I changed it to fire every other revoulition and got 1800 plus. The tachometer on my Dash was reading a steady 1000 RPM after warm up. Which is slightly high due to the fact that it was running on muffs. It normally Idols around 900 on the dash tach. If anyone knows of another tachometer that will work for the V4 please let me know. I just want to be positive that my tachometer is correct before I try changing the prop pitch

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This one says it will do any 2 stroke or 4 stroke from 1 to 12 cylinders:
https://www.amazon.com/Timorn-Replac...2s9dHJ1ZQ&th=1

The link doesn't work, could you screen shot what your talking about? I one I got was a timron brand but it said it works up to 3 cyl 2 stroke and 12 cyl. 4 stroke.i had to read the fine print.

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Originally Posted by huntersdad

The link doesn't work, could you screen shot what your talking about? I one I got was a timron brand but it said it works up to 3 cyl 2 stroke and 12 cyl. 4 stroke.i had to read the fine print.

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its on amazon for $13.49 and called
Tachometer for Small Engine,Inductive Hour Meter for 2 Stroke & 4 Stroke Small Engine, Timorn Replaceable Battery Waterproof Tachometer for Chainsaw Marine ATV Motorcycle UTV Engine (Black)

If you ran it up to 6,000 or over and it hit the rev limiter I’d say your tach is pretty accurate. If it is a 13-19 would drag it back close to 5900-6000. 13/21 would put it right in the operating range. 19 would maintain your hole shot with little not able difference. 21 would slow your hole shot a little but give you more top speed and keep you in operating range for that motor. Ideal situation is have someone you could borrow a prop from. Some dealers actually have used props around the will loan you.

There is a prop shop close by, I will call them and see if they have something I can possibly borrow or purchase at a reasonable price. I'm just going to go with aluminum for now until I know it works and then switch to stainless

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Quote:

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Originally Posted by huntersdad

There is a prop shop close by, I will call them and see if they have something I can possibly borrow or purchase at a reasonable price. I'm just going to go with aluminum for now until I know it works and then switch to stainless

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Honestly you might end up worse doing that. A SS prop will likely have more cupping, higher rake and less flex. Putting a 2" higher pitch alum might actually cause your rpm stay the same, or increase and wind up with less speed.

Cray is right about the tach, I think back then they had a rev limiter (stock powerpack) of like 6150rpm. It might even be printed on the powerpack.

I had a 94 Javelin 17’ hull with a Johnson 115. The Raker 20 was a good all around prop for my rig with a heavy stern from the fuel tank and 3 batteries in the back. I targeted 5500 as my WOT rpm. It would turn a 22 Raker with a light load but the hole shot was beyond awful, even with a full front livewell and weights up front. The best handling prop ok that boat was an old Shooter-it jumped out of the hole but lost a couple mph off the top end by switching to a four blade.

What was the 4 blade pitch? I don't care so much about overall speed as long as I can get my rpm in range when I put the throttle down.

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21p Renegade, could have sworn it was a Shooter prop but my old boat records say it wasn’t. I lost a couple rpm’s off the top when compared to the 3 blade Raker but it lifted the heavy rear end better and it handled better at all speeds.

The boat is rather rear heavy with 3 batteries, motor and fuel. Sitting still, it does sit rather low in the back. A 4 blade may suit me well if I know a good starting pitch. I dont care as much on speed as long as I could lay the throttle down without having to feather it as much to stay in the 4500- 5500 rpm range. With the 3 blade 17 pitch, it jumps and planes quick but also hits the max rpm really fast too. I have to stay around 1/2 to 3/4 rotation of the throttle lever to keep the rpm in range.

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