Struggling to find a good prop for my Nitro 591

Started by Canny, September 17, 2017, 04:18:22 PM

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Canny

2007 591 with a 150 EFI. Currently running a 21p Tempest with large PVS plugs. With one person and tournament load it gets on plane ok maybe 4-5 seconds. However with 2 ppl and same load it takes a good 6-7 seconds and has a ton of bow lift. WOT with 2 ppl it only turns about 4800 RPMs. I may have too much gear in it but I like to be prepared...lol. Any advice


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Lipripper

Quote from: Canny on September 17, 2017, 04:18:22 PM
2007 591 with a 150 EFI. Currently running a 21p Tempest with large PVS plugs. With one person and tournament load it gets on plane ok maybe 4-5 seconds. However with 2 ppl and same load it takes a good 6-7 seconds and has a ton of bow lift. WOT with 2 ppl it only turns about 4800 RPMs. I may have too much gear in it but I like to be prepared...lol. Any advice


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~shhh Never use them words around here  lo lo

Kats Rule And Bass Drool.Viet Nam Vet

Bud Kennedy

Since you mentioned it.....Just what is your load and and where is it located in the boat. Your prop seems pretty common and I might want to check all the other stuff first before getting into a game of swap a prop.  It would also be good information to know what your prop to pad measurement is.  From what you are saying your motor could be a tad deep.  With your bow lift as you describe you are for the most part just plowing water.  Once you balance your load and have your prop at the right depth then you has some reasons to make changes.  An example might be moving to a 4 blade prop as a possible place to start but you certainly need to know the other stuff first.

Your load rating is probably in the area of 750 lbs.  In that load you have to account for people, equipment, fuel, batteries.  It does not take long to overload a 150.

Canny

Quote from: Bud Kennedy on September 17, 2017, 04:29:55 PM
Since you mentioned it.....Just what is your load and and where is it located in the boat. Your prop seems pretty common and I might want to check all the other stuff first before getting into a game of swap a prop.  It would also be good information to know what your prop to pad measurement is.  From what you are saying your motor could be a tad deep.  With your bow lift as you describe you are for the most part just plowing water.  Once you balance your load and have your prop at the right depth then you has some reasons to make changes.  An example might be moving to a 4 blade prop as a possible place to start but you certainly need to know the other stuff first.

Your load rating is probably in the area of 750 lbs.  In that load you have to account for people, equipment, fuel, batteries.  It does not take long to overload a 150.

Yeah I have all of my tackle in the middle storage on the bow. About 10 3700 series boxes and 4 plastic shoe boxes. Rods in starboard box. life jackets dip net etc in port side. Rear boxes have miscellaneous items.

I've looked at moving to a 4 blade prop but I haven't checked my prop height above pad. Any ideas on what distance it should be? I don't have a jack plate so I would have to have the motor removed and raised to new height using adjustment holes on mounting bracket.


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Bud Kennedy

Typical starting point would be 3 1/2" below pad.  Too bad you don't have a jack plate it sure makes it a lot easier to adjust this measurement.  We have heard from others with the same issue and it is not uncommon to have them come back and say they are 6" below pad.  Once adjusted they see improvement all around.

I am a firm believer in knowing the  prop to pad as the first starting point to start exploring performance improvements.  I am running an old Ranger with a 4 blade on a 150 and had to do the same adjustment.  Thankfully I had a jack plate.  I now am Running 3 1/2" and the boat is doing just great with no more plowing and a reasonable on plane time with two people.  Like most I carry entirely too much stuff also

Canny

Quote from: Bud Kennedy on September 17, 2017, 04:48:21 PM
Typical starting point would be 3 1/2" below pad.  Too bad you don't have a jack plate it sure makes it a lot easier to adjust this measurement.  We have heard from others with the same issue and it is not uncommon to have them come back and say they are 6" below pad.  Once adjusted they see improvement all around.

I am a firm believer in knowing the  prop to pad as the first starting point to start exploring performance improvements.  I am running an old Ranger with a 4 blade on a 150 and had to do the same adjustment.  Thankfully I had a jack plate.  I now am Running 3 1/2" and the boat is doing just great with no more plowing and a reasonable on plane time with two people.  Like most I carry entirely too much stuff also

Finally got around to checking the pad measurement. I'm running just under 3.5" at 3.3" so it's as close as I can get without a jackplate as the hole spacing on the motor mounts are 1" center to center. Did some weight trimming and redistribution to see if it helps.


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Bud Kennedy

Well your measurement is about right.  Hope the load balance helps.  I guess you are a prime candidate for the swap a prop program.  Time to check with a prop pro and get their opinion or at least find a four blade to try before you buy.  Happy Hunting.  You might want to PM Princeton Man about the prop specialist he used.  I know he is very happy with the results.

Princeton_Man

At WOT your motor should be turning closer to 5500-5800 and unless you have a very excessive load I'd expect you be spinning the crap out of that 21p. What's your speed at 4800 RPM? I would think you'd be running a 23p 4blade or a 24p 3 blade.

Are you and your co big guys?
Stratos 285 XL Pro 150 Evinrude ETEC

Dobyns Rods - LSCR Club

Captsteve

not to Jack the thread, but what is the pad ?

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Steve
Headed for the Lake

Canny

Quote from: Princeton_Man on September 19, 2017, 08:02:52 PM
At WOT your motor should be turning closer to 5500-5800 and unless you have a very excessive load I'd expect you be spinning the crap out of that 21p. What's your speed at 4800 RPM? I would think you'd be running a 23p 4blade or a 24p 3 blade.

Are you and your co big guys?

The boat came from factory with 24p and it wouldn't get on pad at all. Prop was switched out for the 21p it has now. Going to see how it does with weight trimmed and I'll report back


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Princeton_Man

Quote from: Captsteve on September 19, 2017, 09:14:00 PM
not to Jack the thread, but what is the pad ?

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The pad is that bottom step on the hull. Typical on glass bassboats but there are a few tin boats with stepped hulls.
Stratos 285 XL Pro 150 Evinrude ETEC

Dobyns Rods - LSCR Club

Captsteve

Quote from: Princeton_Man on September 20, 2017, 08:06:41 AM
The pad is that bottom step on the hull. Typical on glass bassboats but there are a few tin boats with stepped hulls.
thanx

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Steve
Headed for the Lake

FloridaFishinFool

Quote from: Canny on September 19, 2017, 09:16:46 PM
The boat came from factory with 24p and it wouldn't get on pad at all. Prop was switched out for the 21p it has now. Going to see how it does with weight trimmed and I'll report back


I know I am late to the party, but correct pitch is usually chosen based on specs. Use your owner manual to find out WOT maximum rpm, and dial in the pitch of the prop to reach that specific rpm at wide open throttle. Too low of pitch causes the motor to over rev, and too high of pitch causes the motor to never reach full power at WOT.

Attach a tachometer to the motor and see where your rpm's are now at WOT without over revving the motor.

This is how I learned to do it and still do with desired goal to be as close to book specs on maximum rpm at WOT.
Words are the exercise for the brain. Words are life expressed... without words we die a slow meaningless death. Silence to the grave is no way to go! So live! Use words! Power of the pen is sharper than any sword! Make it so! Mom said don't surround yourself with idiots! Fly higher than the Eagles... and don't run with the turkeys! Deus Vult!

Bud Kennedy


FloridaFishinFool

Quote from: Bud Kennedy on September 20, 2017, 10:39:55 AM
Attached is a link for the correct way to measure prop to pad

http://www.stevescustomprops.com/faq.html

Yep. It said the same thing I said just worded differently:

"A propeller is designed to control the engine's RPM and hold it at wide open throttle to the recommended RPM range specified by the manufacturer of a motor."

Achieve this, and the pitch is correct.
Words are the exercise for the brain. Words are life expressed... without words we die a slow meaningless death. Silence to the grave is no way to go! So live! Use words! Power of the pen is sharper than any sword! Make it so! Mom said don't surround yourself with idiots! Fly higher than the Eagles... and don't run with the turkeys! Deus Vult!

Canny

Well seems the boat is just sensitive to weight distribution. Moved all tackle to behind seats and have minimal weight on the bow. Pulled one PVS plug from the Tempest 21p, so I'm running 2 large plugs and 1 missing plug. Hole shot is good, WOT 5800 RPMs at 60 mph


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Princeton_Man

Quote from: Canny on September 23, 2017, 05:26:27 PM
Well seems the boat is just sensitive to weight distribution. Moved all tackle to behind seats and have minimal weight on the bow. Pulled one PVS plug from the Tempest 21p, so I'm running 2 large plugs and 1 missing plug. Hole shot is good, WOT 5800 RPMs at 60 mph


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Now that sounds about right! ~c~
Stratos 285 XL Pro 150 Evinrude ETEC

Dobyns Rods - LSCR Club

Canny

Quote from: Princeton_Man on September 23, 2017, 06:39:55 PM
Now that sounds about right! ~c~

Yeah it just showed to be finicky regarding weight. We used to have a skeeter 186 with 150 VMAX and it was a slouch coming out of the hole with a heavy tournament load. Once we changed it up it shot out, can't believe I didn't remember this before...lol. I am concerned that the 5800 RPMs might be on the line of what the engine is designed to do. I'm swapping a 24p Tempest for a 22p Tempest. Maybe that 22 will get my RPMs down in a more comfortable range such as 5500 RPMs.


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FloridaFishinFool

Quote from: Canny on September 23, 2017, 06:43:11 PM
I am concerned that the 5800 RPMs might be on the line of what the engine is designed to do. I'm swapping a 24p Tempest for a 22p Tempest. Maybe that 22 will get my RPMs down in a more comfortable range such as 5500 RPMs.

To reduce rpm's you gotta go up in pitch, not down. One number change, such as from 24 pitch to 25 pitch reduces rpm's approximately 150rpm's for each step up or down.

Going down to a 22 pitch from a 24 should increase rpm's by approximately 300 rpm's to around 6100 WOT.

So you may consider raising your pitch to 26 if you want a 300 rpm reduction.
Words are the exercise for the brain. Words are life expressed... without words we die a slow meaningless death. Silence to the grave is no way to go! So live! Use words! Power of the pen is sharper than any sword! Make it so! Mom said don't surround yourself with idiots! Fly higher than the Eagles... and don't run with the turkeys! Deus Vult!

Canny

Quote from: FloridaFishinFool on September 23, 2017, 06:47:18 PM
To reduce rpm's you gotta go up in pitch, not down. One number change, such as from 24 pitch to 25 pitch reduces rpm's approximately 150rpm's for each step up or down.

Going down to a 22 pitch from a 24 should increase rpm's by approximately 300 rpm's to around 6100 WOT.

So you may consider raising your pitch to 26 if you want a 300 rpm reduction.

I know. Im not running a 24p now, I'm running a 21p. I just so happen to have a 24p laying around that I'm going to swap for a 22p. Thus I will be raising my pitch from 21 to 22 and dropping my RPMs at WOT


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