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RPM Readings and Prop Selection

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MrGiggles
Posts: 268
2
Location: Springfield, MO

RPM Readings and Prop Selection

Post by MrGiggles »

Finally got the tach installed and hooked up in my bass boat.

It's got an 84 Mercury 60 with the factory Quicksilver 10 3/8" by 13 pitch prop. I ordered the Turning Point Hustler replacement (identical to what's on it) before I put the tach on, thinking that the boat runs well enough as is, but that might've been preemptive.

Running solo, I'm getting good 25mph cruise at 4000 RPM, at WOT goes 32mph at 6200 RPM. Seems under propped to me? The prop does have a pretty good chip in one blade (that's why I ordered a new one), but I never noticed much of a difference in performance before or after.

Performance wise, the boat has no issues at all getting on plane, but is pretty lackluster in the speed department. It's a 17' Tracker deep V.

A friend of mine has the same boat with a 60 Evinrude, and he runs a stainless 15p, but I'm not sure if the gear ratios are the same. His boat is a little faster.

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DaleH
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Posts: 2389
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RPM Readings and Prop Selection

Post by DaleH »

Did you try putting your boat through this calculator yet?

https://www.forum.tinboats.net/viewtopi ... =4&t=37433

Sounds like you could step up to a 15” pitch prop. But let me ask you this, what do you usually run, you alone? Or with a couple friends? Or with a TON of gear? Put all that into that calculator - honestly (I weigh ALL gear carried aboard) - and you’ll get good results.

I’ve propped ~8 boats so far file using that calculator and where I could used the new pressed aluminum props by Turning Point Propellers. SS prop performance at an aluminum prop price; they are unbelievable! I’d liked them soooooo much that when I bought the new 21’ offshore deep-V frp boat this year, I ended up putting one of their 4-blade stainless steel props on it, and the results were “spot on” using their calculator, < 200 off the maximum RPM with the load usually carried & half fuel.

On my 16’ skiff and 60hp OMC motor, I also used one of their 4-blade pressed aluminum props, as it was good for the load of 2 people up to 5 people, without lugging the motor. I turned in at least 6.1K WOT by myself and 5800 even when carrying 5 people, that prop was amazing! If you need to carry a load, 4-blade props offer outstanding results in acceleration and carrying capacity. Yes, you do sacrifice a few MPH at WOT, but the results overall are far worth it.
#1) 1st tin rebuild, 18' Lund http://forum.tinboats.net/viewtopic.php?f=21&t=36583
#2) 25' Parker refurb from EMPTY hull http://www.classicparker.com/phpBB3/vie ... p?f=15&t=6
#3) 16' V-tin rebuild http://forum.tinboats.net/viewtopic.php?f=21&t=36465
#4 Procraft SV14
#5) 16' Starcraft entirely NEW Transom Skins http://forum.tinboats.net/viewtopic.php?f=3&t=37548

MrGiggles
Posts: 268
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Location: Springfield, MO

RPM Readings and Prop Selection

Post by MrGiggles »

DaleH wrote:Did you try putting your boat through this calculator yet?

https://www.forum.tinboats.net/viewtopi ... =4&t=37433

Sounds like you could step up to a 15” pitch prop. But let me ask you this, what do you usually run, you alone? Or with a couple friends? Or with a TON of gear? Put all that into that calculator - honestly (I weigh ALL gear carried aboard) - and you’ll get good results.

I’ve propped ~8 boats so far file using that calculator and where I could used the new pressed aluminum props by Turning Point Propellers. SS prop performance at an aluminum prop price; they are unbelievable! I’d liked them soooooo much that when I bought the new 21’ offshore deep-V frp boat this year, I ended up putting one of their 4-blade stainless steel props on it, and the results were “spot on” using their calculator, < 200 off the maximum RPM with the load usually carried & half fuel.

On my 16’ skiff and 60hp OMC motor, I also used one of their 4-blade pressed aluminum props, as it was good for the load of 2 people up to 5 people, without lugging the motor. I turned in at least 6.1K WOT by myself and 5800 even when carrying 5 people, that prop was amazing! If you need to carry a load, 4-blade props offer outstanding results in acceleration and carrying capacity. Yes, you do sacrifice a few MPH at WOT, but the results overall are far worth it.
Usually solo, but I'd like to have some headroom, so if a couple buddies come along it will plane.

I did try that calculator, they only go down to 1990 on Mercs, but the recommended prop is close to factory, 10.5x13.

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Pappy
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Posts: 2842
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Location: Central Florida

RPM Readings and Prop Selection

Post by Pappy »

Best way to prop a boat is to be at or near the top limit of the RPM band with your average load onboard. Load and weight distribution plays a big part in performance.
It's not the end of the world if you are a touch past the recommended RPM with a light load.

MrGiggles
Posts: 268
2
Location: Springfield, MO

RPM Readings and Prop Selection

Post by MrGiggles »

Turning point says 1 pitch is good for 3-400 RPM. Going to a 14 should be around 5800, a little high but that's the headroom I was wanting.

Thanks for the advice everyone.

MrGiggles
Posts: 268
2
Location: Springfield, MO

RPM Readings and Prop Selection

Post by MrGiggles »

MrGiggles wrote:Turning point says 1 pitch is good for 3-400 RPM. Going to a 14 should be around 5800, a little high but that's the headroom I was wanting.

Thanks for the advice everyone.
Just to update, got the 14 pitch put on and tried it last night. WOT RPM is perfect, maybe a touch high. Holeshot is a little worse but that is to be expected.

I may get another in 13 pitch for running heavily loaded, although I will have to try the 14 with a couple passengers first and see how it does.

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Stumpalump
Posts: 809
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RPM Readings and Prop Selection

Post by Stumpalump »

Did it run the same mph?
1991 18' Valco Bayrunner Evenrude 48 SPL

Arizona

MrGiggles
Posts: 268
2
Location: Springfield, MO

RPM Readings and Prop Selection

Post by MrGiggles »

Stumpalump wrote:Did it run the same mph?
33mph now. Top speed before was 31.

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gatorglenn
Posts: 412
4

RPM Readings and Prop Selection

Post by gatorglenn »

I would put a 13p 4 blade Spitfire on. Rpms should be where you are with the 14p, if it’s a 3 blade. But you’ll gain the better holeshot and won’t loose anything at all with a heavy load. It will be 1 maybe 2 mph slower on the top. But handling will be much better.


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Badbubba88
Posts: 12
Joined: 25 Apr 2019, 12:54

RPM Readings and Prop Selection

Post by Badbubba88 »

Hello all,

I'm running a 1986 15 hp 2 stroke Evenrude on a 1972 Alumacraft deep-V at W.O.T. i'm getting 18 MPH an 5,450 RPM using a Aluminum Solas 9 1/4 x 10" prop 13 spline. Looking to get the RPM in the 6500 range and wanting a little help as this is the first J-Boat project. Was told after research the rpm range is 5,500 to 7,000 and ideal range for max hp would be 6,250. i need more speed to get on plain with 2 people maxed out at 12 mph and i'm already over propped so what is me best option for pitch to correct my situation. With 2 ppl hull and 2 batteries trolling motor plywood decking and gear I'm at approximately 700 lbs including the 15 hp motor. where as just myself in the boat with same setup I'm getting 18-19 mph. Help

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bcbouy
Posts: 1381
9
Location: british columbia canada

RPM Readings and Prop Selection

Post by bcbouy »

i put a bad chip and slight warp to my 13.5x15 and the prop wizard recommended a 13.25x19p as an alternative.seems a little bit high for pitch,but i'm going to give it a go anyway.i would actually like to lose a little bottom end holeshot so i can troll a little slower.when my evinrude touch troll control is running at 600 rpm it's a little bit too much vibration.my engine is a 40 etec.
if all else fails....stop using all else

nccatfisher
Posts: 516
6

RPM Readings and Prop Selection

Post by nccatfisher »

I am betting a 19P will be waaaaaay too much prop for that 40. You didn't elaborate on what size boat etc. but I can't remember ever running a 19 on a 40.

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bcbouy
Posts: 1381
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Location: british columbia canada

RPM Readings and Prop Selection

Post by bcbouy »

it's not so much the size of the boat but all the extra weight from the gear and batteries (3 group 31 agm's) probably well over 150# just in battery weight without gas tanks and fishing gear,anchors,cooler.i'm probably carrying close to 700 pounds in the boat when fully geared up with 2 people.my 15p is leaving almost 500 rpm's on the table with just me in it.
if all else fails....stop using all else

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