aluminum vs steel prop

[Zum]

Holy pie man...easy
Pretty sure it was meant to be funny,with some truth in there as well.
Must be hot down there,chill.

 

[Brine]

Just clocked in.....

cleaning in progress.....

 

[mean16]

i'm not wanting to make something out of nothing here, just getting opinions. the guy with the props also has a good used 2 blade that i could get but i have been told a 3 blade is the way to go. like i said in previous posts i'm new to jon boats and small motors, i'm just looking for the best bang for my buck. this 7.5 has to push the boat faster than it does now, i'm not kidding when i say it's slow at full throttle 5-7mph at a guess. with the prop being ate up as bad as it is i only ran it at about half throttle. i just got the boat this past friday and the motor 2 weeks ago. the day i got the motor i put it on a 1430 i had and it did ok with a person on the front bench but the boat was a suicide boat, a good gust of wind is all it would have taken and i would have been swimmin' so i sold it thursday and got this 1636. i just want to go faster than 5mph so what is my best option 2 or 3 blade?

 

[Brine]

 

[Brine]

I'll be interested to hear your results. I've got a 7.5 I'm using on a 16 footer myself. Won't be water testing it for a while though.

 

[Zum]

Lol,Brine.
I'm guessing like someone suggested before,a 3 blade with enough pitch to get you close to planeing.
You'll be running your motor at it highest rpm's and it still may not plane.
If you don't plane you'll never get much for speed,,,not sure if your motor is big enough.
Maybe someones running close to the same setup,they'd could be more help.

 

[Brine]

I suspect you're right Zum. I fish 90% electric only but a few state parks that have 9.9 restrictions, and seeing how the 7.5 was a gift from an x-member on here.....It'll have to do. :LOL2:

 

[Rat]

For all out high end you need the two blade; for hole shots you need the three blade - all else being equal. But all else is rarely equal.

A two blade prop will give more vibration in the lower RPM range; if you troll with the gas motor this will equal more stress on the drive train and transom. A three blade is better balanced and will perform better at low RPM and, generally, through the whole RPM range up to about 2/3 throttle where the characteristics of the two blade really begin to outperform.

The trick is to get a good hole shot with good top end, quality 3 blade props will do this much better than 2 blade props. A three blade prop can be 'massaged' by a prop shop to perform better through the whole range than a factory 2 blade; of course the same can be said of a custom 2 blade as well.

Considering the use of the boat and the fact that 'most' of us go out pretty loaded I would start with a good 3 blade prop and tune it from there. Using a Dole-Fin or equivalent will allow you to jump on plane quicker as well as give you some better steering control while on plane. They can cause more drag lowering top end slightly if the motor height isn't perfect tho; but the trade-off is usually worth it. Playing with the diameter and the pitch of the prop will get you where you need to be with your motor. Ideally you want to get out of the hole as fast as you can and get the most top end speed while hitting the RPM your motor suggests.

The real key is getting the right pitch and diameter for WOT and then 'massaging' the prop for better low end performance or to negate ventilation. This is probably more than you want to do on such a small craft though.

IMO 2 blade props should only be used on high speed hulls designed for super high top end speeds, and trolling-motors.

Some good pointers I learned about all this long ago:
1) Make sure your motor is as high as it can be; get as much of the lower unit out of the water as you can. Mine is high enough that it ventilates in tight turns, which is fine with me; it means I can get as much out of her on a straight run as I can.
2) Use a Dole-Fin or trim tabs, they work very well at getting stern heavy boats out and on plane fast. A Dole-Fin will also halp with steering while running on plane.
3) Get the right diameter and pitch prop. Start with the factory sized prop and adjust from there; you will need a GPS (for speed) and a tach for RPMS to dial a new prop in right.
4) Do all this with the normal load of the boat. It doesn't do much good to prop the hull with just yu in it and then add 800 pounds of people and gear; you will be under proped then.

 

[Waterwings]

:-k All of this makes me glad I fish electric-only 8)

 

[mean16]

thanks for the info man. i'm registering the boat and trailer tomorrow and will get the prop next week (payday) is it normally pretty expensive for a shop to work on them? the guy said i can go from 8-11 pitch at the same cost but he said a 10 would probably be best. i don't know much about this stuff so what would you say? the boat is pretty heavy and most of the time i will have about 400-500lbs plus the weight of the motor on the boat for now, but i would like to deck the floor one of these days

 

[mean16]

here is my project... don't laugh!
https://i325.photobucket.com/albums/k390/1996gmcjimmy/1636%20monark/1636.jpg
the prop
https://i325.photobucket.com/albums/k390/1996gmcjimmy/1636%20monark/prop1.jpg
some nice seats i picked up for $24 each from the same guy with the prop
https://i325.photobucket.com/albums/k390/1996gmcjimmy/1636%20monark/seat.jpg

 

[mean16]

how can i find out what year the motor is?

 

[Brine]

Nothing to laugh at Man. Nice rig.

FYI, in your photobucket account when you choose to upload pics, there is a option to upload them to a specific size. Click the more options link right below the Upload button, then choose the 640 x 480 one, and your pics can then be posted straight to the site.

Also, I'm pretty sure you can check the serial number on the motor and cross reference the year it was made. If you need help, there are enough motorheads on here to help ya out.

Good luck!

 

[Quackrstackr]

Yikes. :shock:

After looking at your prop, I'm going to go out on a limb and say regardless of what you do.. you will see an improvement.

 

[Whoopbass]

Yikes. :shock:

After looking at your prop, I'm going to go out on a limb and say regardless of what you do.. you will see an improvement.

You really think so? The prop doesn't look that bad to me. Looks like its just missing some paint and the edges are pretty worn.
I'm still sticking with there is no way to get any noticeable performance out of that motor (i'm assuming its running fine). It might seem a tad faster the first or second time he's out but its going to turn back into a slug soon and he's going to want more power which will mean a new outboard like a 15-25 hp.
I've ran props with gouges, large nicks and pieces out of them and a then replaced them with a new prop and the performance was always the same.

I would buy a cheap compression gauge and see what it reads before I dumped money into that motor. That motor should be able to plane that bare bones boat out with just you in it but when you start adding weight that motor is just to small.
That's a 1970's motor by the looks of it. Find your serial # and then compare it to this: https://stores.ebay.com/Outboardnuts/Mercury-Year-Lookup.html

 

[Rat]

That prop doesn't look to be in bad shape really, but who knows if it is even close to being the correct prop for that hull. I think you will be happier with a good 3 blade prop. I just realized that this thread was about Alu vs SS. I would stay with Aluminum on this motor; just because a SS will cost more than the entire motor is worth! Really on a small craft with moderate speeds an Alum. prop is fine and I doubt you will see a difference in the two alloys. Keep the 2 blade in the boat as a spare and throw in some cotter pins as well and whatever else you need to change the prop.

 

[Quackrstackr]

I was just going by the blade geometry and a quick picture search for equivalent props.

My trolling motor has more aggressive blade geometry. :lol:

 

[mean16]

the guy showed me a good 2 blade and there is a big difference in the width across the blades and length of blades compaired to mine. aluminum 3 blade to come next week! think i might paint my boat trailer and truck matching camo

 

[Quackrstackr]

the guy showed me a good 2 blade and there is a big difference in the width across the blades and length of blades compaired to mine.

That's what I was thinking.

Your prop looks just like what a mud motor prop looks like after several hours of grinding through mud and debris... and when it is time to replace them.

 

[perchin]

mean16,
what supplier did you order from? I have not been able to locate one yet.