Stock prop VS aftermarket

superjay

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Apr 7, 2008
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28
I have a 1995 20hp mariner on a 14" aluminum, It has the stock 13P prop that came with the motor. The operating ranger is 5500-6000rpm, Iam getting about 5600rpm with just me and a full tank (25L) in the boat and about 45km/h when trimmed out on flat water, The prop is 13 years old and has a few very small nicks in it that have been touched up by a shop and it shows its age, it is not smooth at all as a new painted prop would be. Iam wondering if I will see a noticable change if I go to an aftermarket prop either a Solas Amita, or a Michigan Wheel vortex those are the two that come up on Iboats prop finder which is probobly where I will order from. I would probobly drop down to a 12P prop as well, but mainly just wondering if I will see any significant changes with a newer prop? Is there is a certain brand that is recomended for this type of boat/motor setup? Just recreational boating, getting to fishing holes, and enjoying being out on the water.
 

jay_merrill

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Dec 5, 2007
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Re: Stock prop VS aftermarket

Since you are only 100 rpm over the bottom end of the acceptable WOT range, you definately need to do something.

I am wondering, however, about a 13" prop/20hp motor having so much difficulty with a 14' tinny. Is the boat heavy relative to other 14' boats? Do you load the boat up quite a bit? I may just be jumping the gun on this, and a 13" prop may be simply be too much prop for the boat, but it doesn't seem like it should be.

Regardless, an aftermarket prop may outperform a stock aluminum prop. This is particularly true if the replacement is a well designed stainless steel prop. I've even see increased performance in a prop of the same diameter and pitch. I went from a 15" pitch, aluminum Michigan Match wheel on my boat, to a 15" pitch, stainless, cupped Powertech prop. The props are the same diameter also. With this simple change, I picked up 150 WOT rpm, which is something that I did not expect.
 

superjay

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Apr 7, 2008
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Re: Stock prop VS aftermarket

Since you are only 100 rpm over the bottom end of the acceptable WOT range, you definately need to do something.
Iam still within the acceptable range so what do you mean I definately need to do something?

I am wondering, however, about a 13" prop/20hp motor having so much difficulty with a 14' tinny. Is the boat heavy relative to other 14' boats? Do you load the boat up quite a bit? I may just be jumping the gun on this, and a 13" prop may be simply be too much prop for the boat, but it doesn't seem like it should be.
What do you mean by having so much difficulty with a 14' tinny? I don't think it has any difficulty moving my boat, it might be a bit heavier then others but not by much, it is a welded and has a side console so its probobly a bit heavier then a standard 14' tiller but iam sure its within 150lbs or so
Regardless, an aftermarket prop may outperform a stock aluminum prop. This is particularly true if the replacement is a well designed stainless steel prop. I've even see increased performance in a prop of the same diameter and pitch. I went from a 15" pitch, aluminum Michigan Match wheel on my boat, to a 15" pitch, stainless, cupped Powertech prop. The props are the same diameter also. With this simple change, I picked up 150 WOT rpm, which is something that I did not expect.
This was my main concern if an aftermarket prop will simply outperform a stock prop even if the stock prop is properly pitched, however I will be sticking with aluminum mainly due to the price
 

180shabah

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Re: Stock prop VS aftermarket

however I will be sticking with aluminum mainly due to the price

Check out turning point propellers, they make "high performance" aluminum props, I'm not sure what they have for the smaller engines though.
 

steelespike

Supreme Mariner
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Apr 26, 2002
Messages
19,069
Re: Stock prop VS aftermarket

Its probably time for a new prop.Props do wear out.
Turning point has the Rascal in 13" and 11" I would go with the 11.
Stainless performance at aluminum prices.They generally give an overall performance improvement.Not sure of your present mph I'm guessing about 23-25 mph. The Rascal will allow a higher engine height give better hole shot
better load carrying,resist ventilation(cavitation.As far as speed goes it could be a few tenths or maybe a couple of mph.better.Simply raising the motor will add speed and you can raise it higher with the Rascal.
 

ACracing

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Apr 27, 2009
Messages
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Re: Stock prop VS aftermarket

I have a 1995 20hp mariner on a 14" aluminum, It has the stock 13P prop that came with the motor. The operating ranger is 5500-6000rpm, Iam getting about 5600rpm with just me and a full tank (25L) in the boat and about 45km/h when trimmed out on flat water, The prop is 13 years old and has a few very small nicks in it that have been touched up by a shop and it shows its age, it is not smooth at all as a new painted prop would be. Iam wondering if I will see a noticable change if I go to an aftermarket prop either a Solas Amita, or a Michigan Wheel vortex those are the two that come up on Iboats prop finder which is probobly where I will order from. I would probobly drop down to a 12P prop as well, but mainly just wondering if I will see any significant changes with a newer prop? Is there is a certain brand that is recomended for this type of boat/motor setup? Just recreational boating, getting to fishing holes, and enjoying being out on the water.

I have a Yamaha 25. I went through the prop thing for some time. If you drop down from a 13 to 12 pitch, you will most likely experience a better hole shot, however, you could posibly experience some decrease in top end speeds. The rule of thumb is: if you go from aluminum to stainless, you should decrease pitch. If you go to a stainless 12p, and do not like the results, have someone add some cup to the prop. Also, keep in mind, adding a jackpalte could dramatically increase performance. A friend of mine had a 30hp Tohatsu, he gained (approx) 5mph on top end, of course this was with a small fiberglass boat(using gps). Lastly, keep in mind I am not a boat mechanic,this is just from personal experience. Lastly, changes in speed are more pronounced as hp is increased (ex. 25hp vs. 200hp). Hope this helps!
 

jay_merrill

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Re: Stock prop VS aftermarket

By running a prop that only give you 100 rpm over the bottom of the acceptable WOT rpm range, you severely limit your ability to operate the boat in any configuration other than what you are doing now. If you add any appreciable amount of weight, such as a bit of extra gear or another passenger, the end result will most likely be that of running under the minimum rpm.

That willl mean that your engine will have to run at a very high manifold pressure in order to get whatever rpm level you do manage to achieve. This is a situation that can lead to mechanical damage.

While I don't necessarily subscribe to the theory that outboards should be propped to run somewhat above recommended WOT (which some here do), being so close to the bottom end of the range is something that I do not view as being advisable. Obviously, how you run your boat/motor is up to you, but I think you will find that most folks here will advise you to drop at least two to three inches in pitch, if your performance problems don't turn out to be something other than being pitched too high.

I do recommend examine the "other causes" issue, though. It just seems to me that your motor should push a normally loaded 14' aluminum boat more easily.
 

hwsiii

Commander
Joined
Jan 25, 2009
Messages
2,639
Re: Stock prop VS aftermarket

Superjay, if you change to a 12" prop from the 13" prop in the same exact model prop you have now, you will go from 5,600 RPM to 5,900 RPM, and you should not lose any speed.

SuperjayPropIboat.jpg


H
 

superjay

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Apr 7, 2008
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28
Re: Stock prop VS aftermarket

ok well I think I will be moving down to an 11" pitch prop from all the advice I am getting, where do I find the turning point rascal props? It seems that most of the local shops around here can only get me a mercury prop or "stock" type prop unless I want to wait 6-8 weeks for it to be shipped out here which I don't. I will do some more looking around here locally though. Thanks for all your help so far
 

jay_merrill

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Re: Stock prop VS aftermarket

If you are willing to go with a "stock" prop in another pitch, you might ask your local shops if they will let you test a few wheels to see what they do for your performance. As long as you bring a prop back undamaged, many shops will let you do this. The idea, of course, is to buy one of them, once you figure out which one does the best job.
 

180shabah

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Re: Stock prop VS aftermarket

...where do I find the turning point rascal props? It seems that most of the local shops around here can only get me a mercury prop or "stock" type prop unless I want to wait 6-8 weeks for it to be shipped out here which I don't...

Go to the top of this thread and click "Mariner Props". Looks like $91
 

LoweRider

Seaman Apprentice
Joined
Jul 5, 2008
Messages
44
Re: Stock prop VS aftermarket

I have a 14' tinny with a 9.9 johnson my prop is an aluminum 9 1/4 x 8 here is a video of it running hope it might help you out . http://www.youtube.com/watch?v=M9NfkwVYx0E&feature=channel_page Since this video was taken I have changed the prop to a 9 1/4 x 8 stainless Solas Saturn, I can't wait to see if there is any noticeable difference.:D Can any of you guys guess about how many RPM I am running, I don't have a tach so I really am not sure. Any answers would be helpful, thanks.
 

180shabah

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Re: Stock prop VS aftermarket

Lowe... Start a new thread - and get a tach guessing is useless.
 

superjay

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Apr 7, 2008
Messages
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Re: Stock prop VS aftermarket

Update,

So after a bit of research I decided to check my engine height I took a straighedge along the bottom of the boat to the plate above the propeller (I forget what its called off hand) and the engine is about 2 inches lower then this when trimmed at the 3rd hole, and from what I have read it should be about level or even a bit higher then the bottom of the transom, so the first thing Iam going to do is try moving the engine up a bit, now my problem is that the engine is through bolted on the transom and there aren't any adjustments so Iam wondering if I can pull out the 2 bolts on the lower part fill them(they don't appear to be doing alot anyways) and raise the engine a bit and just use the 2 big C clamp type tighteners on the top of the engine? I would hate to have to drill more holes just to try and see what raising it a bit will do for me? So are the 2 big clamps on the motor enough for this motor?
Thanks
 

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Re: Stock prop VS aftermarket

Yes they will work.They used to do this all the time with racing outboards
much more powerful than your little 20.
Just be sure it has a good grip and pumps water.
raise it a little at a time.They used to add 1/4" sticks on the top of the transom just to hold the height.
 
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