Prop Recommendation: I have all the data :)

[swiss]

Current Specifications

Boat: 1993 Lowe 1448M weight~ 360 lbs 15 foot boat, flat bottom
Motor: 1993 Evinrude 30 HP weight~80 lbs
Gas Tank, Battery, Driver weight ~ 250 lbs

Total Weight ~680 lbs

Current Propeller: 10x13 aluminum (moderate nicks, wear etc)
RPMs = 4600 WOT
Top Speed 29 mph

Conditions
flat water or slight chop
70 degree outside, 62 degree water
motor is mounted up ~2 inches higher running at maximum height/performance

Boat mainly used for fishing/utility, max weight would be 1000lbs, boat, motor, gear and humans

I have gone through the prop charts and to increase the RPM I would need a 4" pitch change going from a 13 to 9, sounds pretty radical?

I believe WOT recommendations are 5200-5500 for this motor?

Recommendations Please, looking for top speed,

Thanks all, I have been digging through threads to get the Tach setup, and raise motor etc.

Steve

 

[hwsiii]

Re: Prop Recommendation: I have all the data

Swiss, I have to go to work right now, but something is wrong. I show that motor as WOT RPM 5,200 to 5,800 RPM with a 2.15 gear ratio. At 4,600 RPM and a 13" prop it would be a negative slip on the prop, and that is not possible. Please check my Specifications on that motor and I will get with you this afternoon.

H

 

[steelespike]

Re: Prop Recommendation: I have all the data

As suggested something is wrong.Probably the tach. What is the tach indication at idle? If idle is set right should be about 700.
Your speed is in the ball park but the rpm doesn't match.
Having to drop to a 9" prop doesn't make sense either.
9" is close to what you would use on a pontoon.

 

[swiss]

Re: Prop Recommendation: I have all the data

The tach is new as I just set it up for this testing. The idle rpm is around 800 and the motor sounds about right at idle. It is hooked into the OMC control via the 3 prong harness. Pole set at 6 on the tach.

Tach seems to respond correctly to increases in throttle. The current prop has damage, not huge chunks or anything but it it worn and has seen the bottom of the lake a few times.

At 4600 tach indication the motor sounds okay. Last time I looked with the cover off of the engine the throttle seems to open up all the way. I will have to double check again.

Compression testing was done this spring and compression was good on both cylinders.

The normal prop I believe for this motor is 10x15 so I was suprised that the 13 was not pushing a higher RPM or indicated RPM.

 

[MikDee]

Re: Prop Recommendation: I have all the data

With the motor off, put it in forward gear, and make sure your carbs are opening fully, then check to see your advance mechanism is reaching it's stop. Aside from that, I'd guess your tach is off? Your speed seems about right. I had an old evinrude big twin 40hp, that didn't seem to be putting out the full power after awhile, sure enough I found the advance mechanism was not working properly

 

[bowman316]

Re: Prop Recommendation: I have all the data

how is your acceleration?
if you have trouble getting on plane, or it takes more than 30 seconds to get on plane, you may want to go down 2 inches in pitch.
a boat that will jump right up on plane is a good indication that you are not over propped.

 

[swiss]

Re: Prop Recommendation: I have all the data

mikdee that helps me on what to check thanks! The boat gets up on plane reasonably well. Can I loose 400 rpm on a worn prop?

I will check throttle tonight

 

[bowman316]

Re: Prop Recommendation: I have all the data

last week i tore up one blade of my prop, just sheared some of the tip, kinda peeled like string cheese.
but it still ran ok, just vibrated the motor a lil more.
the RPM's were uneffected.

 

[hwsiii]

Re: Prop Recommendation: I have all the data

Swiss, that is not a GPS speed you gave us, is it. For a 13" aluminum prop to do 29 MPH with the information I have on your motor, your prop would have to be turning 5,600 RPM. Please check the gear ratio and RPM for your motor. Then check the prop and please give me the manufacturer and model of your prop, and also the series of the prop. Also, if you could can we see a picture of the prop.

H

 

[swiss]

Re: Prop Recommendation: I have all the data

Okay got back from the boys soccer game and here is the findings and answers:

1) The speed was captured using a GPS Garmin Handheld
2.) Checked Mechanical stop and throttle plate, at full stop and wide open
3.) Motor Information
Evinrude: 30
SN: G03240603
Model: VE30ELETA
4.) Propeller Manufacturer unknown, unless somebody recognizes the stamping in the picture.

I do not know how to check the gear ratio, I guess like a car I could turn the propeller by hand by I do not believe I have another frame of reference like a drive shaft that is visible???? I do not remember if I put the motor in gear and turn the prop if the flywheel spins also?

Sounds like I have a bad "Brand New" Tach and that the 10x13 is the right size based on the calculations.

H where the heck did you find that great chart???? I did not see on the prop page on the site?

Pictures included. No laughing at the damage that is why I am going through this exercise.

 

[hwsiii]

Re: Prop Recommendation: I have all the data

Swiss, that is custom software that I designed. But, sorry to say that with that big chunk out of the prop I wouldn't hold my breath that the formula will work for this one. If you go to buy another prop be sureee they will let you exchange it, if it is not hurt.

My recommendation for your prop is a 13" prop in the same model you have now. This is my software for picking props. I used your figure of 1,000 pounds for the total weight.

H

 

[swiss]

Re: Prop Recommendation: I have all the data

Mr. Slater that is one cool piece of software! You should lease to one of the prop companies for use on line ))))

There are actually no major chunks out of the prop, it is more the lighting and my cropping of the photo's. It is well used That is what a Jon Boat is for.

Before ordering I am going to pull another tach out of another boat I have and see what readings I get on that Tach.

Sounds like I should order a 10x13 Michigan prop for the replacement!

 

[hwsiii]

Re: Prop Recommendation: I have all the data

Swiss reread my post. I had the wrong weight setup in the program. I had to edit it and post the new picture. Sorry, I should have double checked. Get the 13" like you have now.

H

 

[swiss]

Re: Prop Recommendation: I have all the data

Thank you all! I am glad I went through this exercise. It has actually taken about a month to research the setup of the tach on this site, study the prop pages and get all the data collected.

As usual you learn a tremendous amount of information on the journey and your motor becomes less scary and your troubleshooting level more comfortable. I have more familarity in cars and once you get past the fact that the motor and gearing look different the mechanics of a combustion motor is a combustion motor.

Great web forum, the people and the amount of knowledge to be learned is very similar to my mustang forums. You know you are a sick man when you just read other posts to learn more about what problems people are having.

 

[MikDee]

Re: Prop Recommendation: I have all the data

You need a new prop I would say don't give up on the tach yet, just try different settings till it reads about right, we know that your speed is about right, meaning your actual rpm should be between 5200-5800rpm. Good Luck

 

[bowman316]

Re: Prop Recommendation: I have all the data

that prop is not that beat up.
i have had much worse looking blades

 

[swiss]

Re: Prop Recommendation: I have all the data

Okay lets get picky now, if money was not an objective which prop?

Michigan Vortex Aluminum
Rascal Turning Point Aluminum
Solas Stainless Steel

??

MikDee I wil check the pole settings on the tach!

Propeller Specifications:

SKUrop #992505Hub #118
Manufacturer: Michigan Wheel
Brand: Vortex XHS
Material: Aluminum
Diameter: 10 - 1/8?
Pitch: 13?
Blades: 3
Rotation: Standard (Clockwise)


SKUrop #r1-1013Hub #22
Manufacturer: Turning Point
Brand: Rascal
Material: Aluminum
Diameter: 10 - 1/8?
Pitch: 13?
Blades: 3
Rotation: Standard (Clockwise)

SKU:#2231-101-13
Manufacturer: Solas
Brand: New Saturn
Material: Stainless Steel
Diameter: 10 - 1/8?
Pitch: 13?
Blades: 3
Rotation: Standard (Clockwise)

 

[bowman316]

Re: Prop Recommendation: I have all the data

i think the brand could matter less.
they are all the exact same pitch and diamater, that is the only thing that makes a difference.

and ss props do not really make much of a difference on a small motor, other than the fact that they may take more of a beating without chipping.

you will not get a cgange in performance unless you change pitch.
if you are happy with your current acceleration, then keep the current pitch.

 

[bryonthefly]

Re: Prop Recommendation: I have all the data

i think the brand could matter less.
they are all the exact same pitch and diamater, that is the only thing that makes a difference.

and ss props do not really make much of a difference on a small motor, other than the fact that they may take more of a beating without chipping.

you will not get a cgange in performance unless you change pitch.
if you are happy with your current acceleration, then keep the current pitch.

Not too sure about that. I have two props that have same diameter and pitch from two different manufacturers that are like comparing night and day, performance wise.

 

[hwsiii]

Re: Prop Recommendation: I have all the data

Swiss, you need to tell us what you intend to use the boat for and how many people you normally carry, as well as other things about your uses. Prop Geometry can be very tricky when you get into stainless props, when you change for one geometry to another. It CAN change how many RPM you are able to turn on your motor by as much as 600 to 800 RPM.
Got to go to work, but will be back tonite.

H