# Which prop for 40 hp Mariner? Updated: Pitch and Dia ?



## sturdi87 (Jun 22, 2010)

I am about to replace my damaged propeller and have been trying to decide what exactly to buy (and for anyone who saw my thread asking about repairing a cracked prop blade with jb weld I did not do it or even try in case you were wondering).

Here is the setup, it is a 1983 40 hp Mariner 2 stroke on a 14' aluminum. The prop that came with the boat and motor is stamped with the number "48 73136 A40 13P." After a little research I determined that it is a Mercury Black Max propeller 10 3/8" diameter and 13"P. 

The first decision is to replace it with a prop of the same specifications or something different? I have been unable to find any information as to what diameter and pitch of prop was original to my particular motor, this prop could have been a replacement for all I know. Before I damaged the prop I gps'd the boat at 29mph in some chop on the ohio river, probably about 3-4". I don't have an RPM guage but here is a video of it running: 
[youtube]<object width="480" height="385"><param name="movie" value="https://www.youtube.com/v/JknUrpKJOXQ&hl=en_US&fs=1&"></param><param name="allowFullScreen" value="true"></param><param name="allowscriptaccess" value="always"></param><embed src="https://www.youtube.com/v/JknUrpKJOXQ&hl=en_US&fs=1&" type="application/x-shockwave-flash" allowscriptaccess="always" allowfullscreen="true" width="480" height="385"></embed></object>[/youtube]
Is there anymore top end to be had? I can open up the throttle a little more from there, when I do the rpm's drop a little, the motor acts like it is choking or something? flooding maybe?

When I actually measured the old prop it was 4 15/16" from the center of the hub to the farthest point on the remaining blades, which comes out to a 9 7/8" diameter. The prop that came on it was already beat up when I bought the package, so I think this explains the missing 1/2" of diameter. The boat seemed like it takes a little long to plane out completely.

I'm in the ohio river, creeks, and backwaters a lot so I am definitely sticking with aluminum. I have been looking at direct replacements (3 blade aluminum 10 3/8" dia 13" pitch); two different props specifically, a Mercury Quicksilver Black Diamond and a Michigan Wheel Vortex XHS. I found some information about the actual features or characteristics of the Vortex XHS (here: https://www.miwheel.com/Propellers/OutboardPropellers/Vortex.aspx) but have not been able to find much information like that for the Black Diamond. How do the features of the black diamond compare? What about michigan wheels exchangeable hub system? pros? cons? vs the standard hub in the black diamond?

Thanks for any input!

Here are links to the props:
https://boatpropellers.iboats.com/M...19217/?session_id=114107940&cart_id=292044272
https://boatpropellers.iboats.com/M...7/624/?session_id=114107940&cart_id=292044272


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## dyeguy1212 (Jun 22, 2010)

I'm no motor expert by any means, so I don't have a whole lot of input. What I do know is I hit 29 easily in my 1648 (with mods), which I'm banking weighs quite a bit more than your 14 footer depending on the load inside the boat. So I'd guess there's speed to be hand, but only a few mph.


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## sturdi87 (Jun 22, 2010)

dyeguy1212 said:


> I'm no motor expert by any means, so I don't have a whole lot of input. What I do know is I hit 29 easily in my 1648 (with mods), which I'm banking weighs quite a bit more than your 14 footer depending on the load inside the boat. So I'd guess there's speed to be hand, but only a few mph.



Thanks dyeguy, actually I was wondering what prop you have on your 40hp mariner? 3 blade? size? pitch?


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## Zum (Jun 22, 2010)

I expected your speed to be higher(thought youd be flying) as well but not knowing the weight or type hull you have it might be all you'll get.
Rpm's are the key thing to buying or getting the right prop.
The sell them tiny tachs down there pretty reasonable priced.
I had a 40hp suzuki with a 10 3/4 by 13 pitch on a 1652 boat,I could have gone to a 14 easily maybe even a 15pitch but didn't bother...even with the 13 was getting 33 gps.
Unless your outboard has some type of governor I don't know why your rpm's would drop when you go full throttle.
Have you done a carb cleaning?


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## Quackrstackr (Jun 22, 2010)

Hard to say without an rpm reading but I took a wag on your setup on a prop wizard and came out with props from 10 3/4 x 12 up to 10 1/8 x 15.

You will drop 200 rpm for every inch of pitch on a prop and you want to run in the recommended rpm range for your motor (I think up to 5500 on yours) without lugging it.

Hard to say about different prop brands/models too without just trying them. They all have slightly different blade geometry and will all run a little differently.


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## sturdi87 (Jun 22, 2010)

Quackrstackr said:


> Hard to say without an rpm reading but I took a wag on your setup on a prop wizard and came out with props from 10 3/4 x 12 up to 10 1/8 x 15.
> 
> You will drop 200 rpm for every inch of pitch on a prop and you want to run in the recommended rpm range for your motor (I think up to 5500 on yours) without lugging it.
> 
> Hard to say about different prop brands/models too without just trying them. They all have slightly different blade geometry and will all run a little differently.



Yeah I was just curious as to if anyone knew any details on the black diamond, such as cupping etc etc as I have been unable to find this. Also I wanted to see if anyone had anything positive or negative to say about the different hubs. But I think I will probably be best off doing a direct replacement and seeing what it does with that (and the difference the 1/2" of diameter that was apparently beaten off before I got my hands on the boat and motor makes). Maybe I should try out one of those little tachs? I was hoping someone would have a comment based on seeing and hearing it run in the video as far as all that?


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## Quackrstackr (Jun 22, 2010)

Hard to say.

Mine doesn't sound anything like that running wao, for sure. :lol:


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## dyeguy1212 (Jun 23, 2010)

sturdi87 said:


> dyeguy1212 said:
> 
> 
> > I'm no motor expert by any means, so I don't have a whole lot of input. What I do know is I hit 29 easily in my 1648 (with mods), which I'm banking weighs quite a bit more than your 14 footer depending on the load inside the boat. So I'd guess there's speed to be hand, but only a few mph.
> ...



3 blade.. the rest is a mystery


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## sturdi87 (Jun 28, 2010)

Went ahead and bought a 10 3/8" dia x 13" pitch Vortex XHS. Showed up today. Test run yielded exact same top end speed results as the old beat up prop. Boat did seem to accelerate much faster as well as plane out better. The most noticeable difference between the new vortex and the old one was that the vortex did not lose grip in turns at higher speeds like the old one did. In relatively wide sweeping turns the old prop lost grip, this was not the case even in much sharper turns at comparable speeds with the vortex.



dyeguy1212 said:


> 3 blade.. the rest is a mystery


If you could copy down whatever numbers are on it, there should be some numbers/letters that is a part number stamped on it. I would really appreciate the information, or anyone else reading this with a 40hp mariner (or merc or yamaha etc for that matter), It would be a great help!


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## sturdi87 (Jun 29, 2010)

I am going to buy a second prop later this week. I want to have a backup prop primarily. But with a propeller that performs fairly well I want to tweak the specs of the second prop and see if I can improve performance. If I do then the prop I just bought becomes the backup, if I don't then the tweaked one will become my backup. Due to this I don't want to change anything too drastically but I do want to try something a little different.

In summary, what I have to go on is this: 
-The GPS top speed was 29mph with a 10 3/8" x 13" pitch black max propeller that was beat up and actually measured 9 7/8" in diameter (missing 1/2" from the diameter size the part number indicated).
-Purchased a replacement 10 3/8" x 13" pitch aluminum propeller and test runs yielded the exact same result of 29mph for top speed measured by the same GPS unit.
-In order to check my measurement technique that I used to determine that the actual diameter of the old prop was only 9 7/8" I took measurements of the new prop in the same way and came up with 10 3/8." When visually compared the old prop appears to be smaller in diameter to me as well.
-Something else to note, the center of the new hub is larger in diameter than the old prop, the old props center fit inside the new with plenty of room to spare, probably around n 1/8" I would guess. So this means that the actual area of the propeller blades on the new prop may be very similar to the area of the propeller blades of the old prop with the smaller diameter.

Some options I'm looking at:
Michigan Wheel Vortex XHS
11 3/8" x 12"
11 1/8" x 13"
10" x 14"
10" x 15"
10 1/8" x 14"
11 1/4" x14

Quicksilver Black Diamond
10 1/2" x 13"
10 3/8" x 14"
10 1/4" x 14"
10 1/4" x 14 1/2"
10" x 15"
10 1/8" x 15"
11 1/2" x 13"

I found one video on youtube so far of a guy with a 40hp that gave information about the prop he was using, it is supposedly a stock 40hp yami on a 1542 war eagle running a 15" pitch quicksilver prop hitting 40.1mph: https://www.youtube.com/watch?v=H5Ur7W9xHVA

Thanks for any input guys! This site has been a ton of help every step of the way!


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## huntinfool (Jun 29, 2010)

I'll check my Yamaha and see what I have on it.


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## Quackrstackr (Jun 29, 2010)

sturdi87 said:


> I found one video on youtube so far of a guy with a 40hp that gave information about the prop he was using, it is supposedly a stock 40hp yami on a 1542 war eagle running a 15" pitch quicksilver prop hitting 40.1mph: https://www.youtube.com/watch?v=H5Ur7W9xHVA



I can't see youtube behind the work firewall but unless that guy is filming his setup along with a realtime gps reading, that's a hard one for me to believe.

I have a buddy with a bare bones 16' WE and 2/yo Yamaha 40 that wouldn't hit 40mph if his life depended on it.

Regardless, 2" of pitch isn't going to give you 11 mph.

Prop diameter doesn't have a lot to do with speed increase or decrease. Increased diameter will give you additional stern lift and better bite (most likely the main reason you aren't slipping the prop in turns anymore).

Different prop styles by different manufacturers are probably going to behave completely different because of differing blade geometry. It's hard to judge the performance of a different brand just by looking at pitch and diameter numbers compared to what you already have. But, solely speaking of top speed, they shouldn't be that much different given equivalent dimensions.


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## sturdi87 (Jun 29, 2010)

huntinfool said:


> I'll check my Yamaha and see what I have on it.


Thanks a lot. My Mariner is one of the Yamaha built ones.




Quackrstackr said:


> I can't see youtube behind the work firewall but unless that guy is filming his setup along with a realtime gps reading, that's a hard one for me to believe.
> 
> I have a buddy with a bare bones 16' WE and 2/yo Yamaha 40 that wouldn't hit 40mph if his life depended on it.
> 
> ...


Yeah it is from the shore so no GPS in the shot, I think I said he was claiming to get 40. Thanks for the info, the new prop I bought is supposed to be "high performance" cupping rake all that and more, at least thats what the box says! haha I thought it might be that. But yes I follow what you are saying I'm just trying to get any bit of knowledge I can because my experience is obviously limited. 

I am going to look into one of those tiny tachs I guess.


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## Quackrstackr (Jun 29, 2010)

Installing a tach is really the only way to dial in your prop.

Even at that, it's hard to call what the change will be by looking on the net at different brands. You almost have to swap around until you find the prop that fits your boat the best and then start playing with pitch/diameter.

That gets kind of spendy when you're running stainless. That's why my Triton is still underpropped.  I can't afford to play with it when the props are nearly $400 a pop.


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## huntinfool (Jun 29, 2010)

I have a power tech prop on mine. go to https://www.ptprop.com/ to view their selections.

I believe the numbers on mine say y850S(or maybe a 6)RC3R126 Also it has 9341780. I am going to try and contact them and see what it is that I actually have.


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## huntinfool (Jun 29, 2010)

Ok my 40hp Yamaha has a 10.75X12 on it. I do not know hw fast it goes (I keep forgetting my GPS) but I will say it hauls...


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## sturdi87 (Jun 29, 2010)

huntinfool said:


> I have a power tech prop on mine. go to https://www.ptprop.com/ to view their selections.
> I believe the numbers on mine say y850S(or maybe a 6)RC3R126 Also it has 9341780. I am going to try and contact them and see what it is that I actually have.


 Thanks a lot for the effort, I can't seem to find anything except for a link to a japanese website that is dead now anyways. Thanks a lot though for the info!



Quackrstackr said:


> Installing a tach is really the only way to dial in your prop.
> 
> Even at that, it's hard to call what the change will be by looking on the net at different brands. You almost have to swap around until you find the prop that fits your boat the best and then start playing with pitch/diameter.
> 
> That gets kind of spendy when you're running stainless. That's why my Triton is still underpropped.  I can't afford to play with it when the props are nearly $400 a pop.



Really, well thanks everything I read seems to focus on the pitch and then next the diameter as the two most important elements, the blade geometry features didn't seem to get much more than a paragraph or side note in a lot of the articles I have read. They all seemed to say in short that rake will affect performance and cupping is essentially good. But of course they probably leave it at that because its probably complicated and there is either a different way to explain it for individual applications or they just don't even know really. haha.

But yeah man that is steep. One of the main reasons why I'm sticking to aluminum, well in addition to the fact that I'm in the ohio river, backwaters, and creeks the majority of the time. But hey check out some of the 4th of July sales going on right now if your looking at all. They probably won't have whatever your looking at on sale but I got one heck of a deal. The prop I bought was originally right around $120 or a little over and I got it for $64 from i boats com


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## sturdi87 (Jun 29, 2010)

huntinfool said:


> Ok my 40hp Yamaha has a 10.75X12 on it. I do not know hw fast it goes (I keep forgetting my GPS) but I will say it hauls...



Well if you would say it hauls leave the GPS at home, because while I think 29 is quick still, it seemed faster when I didn't know it was 29. haha

Thanks a lot for the info. Maybe I have a little too much pitch and a little too small of diameter... maybe I should probably just be happy that it even starts, and ecstatic that it always starts on the first crank, even if it only got 15mph, considering I paid only $700 for the boat, trailer, motor, and a trolling motor. haha. Thanks guys. 

maybe I will get that tach though...


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## Quackrstackr (Jun 29, 2010)

sturdi87 said:


> huntinfool said:
> 
> 
> > Ok my 40hp Yamaha has a 10.75X12 on it. I do not know hw fast it goes (I keep forgetting my GPS) but I will say it hauls...
> ...



:mrgreen: 

Funny how that happens.

Get the tach. That's the only way that you will ever know what you have to work with.


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## huntinfool (Jun 29, 2010)

I'm gonna get a tach and put it on mine and see where I am and then I am going to get the GPS and see what speed I am getting. Then I will know if I need to change anything on my rig.
Try searching power tech propellers. Mine is the SRC3 model, but there are some on there that look even better than mine.


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