# 2018 Mercury EFI 20hp prop



## Duckboat (Apr 24, 2016)

Has anyone used a different prop on these yet with better performance than the Merc prop....stainless perhaps ?


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## LifeOnFly (Aug 1, 2017)

Have the same 2018 efi mercury on a gheenoe lt25 with the stock 10p aluminum it rev limiters going to get a 11.5 and see it works out.


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## Duckboat (Apr 24, 2016)

LifeOnFly said:


> Have the same 2018 efi mercury on a gheenoe lt25 with the stock 10p aluminum it rev limiters going to get a 11.5 and see it works out.


I don’t hit the rev limiter I’m running close say 6160,I want a stainless really but let me know how that 11.5 runs,what brand you going with?


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## LifeOnFly (Aug 1, 2017)

Duckboat said:


> I don’t hit the rev limiter I’m running close say 6160,I want a stainless really but let me know how that 11.5 runs,what brand you going with?


Most likely mercury, trying to pick one up locally within the week.


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## Hugh White (Jan 12, 2019)

Any update on this?


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## LifeOnFly (Aug 1, 2017)

nope still with stock prop... still need one


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## Hugh White (Jan 12, 2019)

Thanks.. I'm about to buy this motor and will be looking for best speed. Thanks


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## Duckboat (Apr 24, 2016)

Well I’ve been out on the water now for like a month an I still have the 9.25 x10stock prop on,by myself with gear Ill get 24mph on some occasions a little more at 6100-6200rpm,with another on board 21-22mph at 5750-5800 rpm....that’s pretty good to me,I’m afraid to waste money on another prop if it’s going to drop my speed or rpm too low ,but all in all this new Merc rips so far I love it


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## Mangofish (Jun 12, 2019)

I have a 2017 LT 25 with the 2019 20 Merc. ordered the BlackMax aluminum 9.25 x10 pitch. alone my Gheenoe runs 27.2 mph and cruises nicely at 23-24 mph according to my Garmin gps. It jumps right out of the hole too. I'm impressed with the prop.


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## Stauter (Jan 20, 2012)

Running a 3 blade stainless Powertech SRT. Major improvement over stock aluminum prop. Better hole shot, top end and boat stays on plane at lower speeds. Took it to the prop shop and added cup for better performance when running the motor elevated on the transom.

Currently working with Jack at Crossroads on a 4 blade SRT to run as skinny as possible


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## Duckboat (Apr 24, 2016)

Mangofish said:


> I have a 2017 LT 25 with the 2019 20 Merc. ordered the BlackMax aluminum 9.25 x10 pitch. alone my Gheenoe runs 27.2 mph and cruises nicely at 23-24 mph according to my Garmin gps. It jumps right out of the hole too. I'm impressed with the prop.


I have a 2018 Merc 20,an it came with the black max 9.25x10,I didn’t have to order it,I’d have to say it’s the fastest aluminum prop


[email protected] said:


> View attachment 78474
> Running a 3 blade stainless Powertech SRT. Major improvement over stock aluminum prop. Better hole shot, top end and boat stays on plane at lower speeds. Took it to the prop shop and added cup for better performance when running the motor elevated on the transom.
> 
> Currently working with Jack at Crossroads on a 4 blade SRT to run as skinny as possible


What size power tech? An I have mine bolted high on the transom too,I don’t know if that stainless would perform better for me...we got different boats....it could,but I’m afraid to waste money on one....but that black max prop is already cupped


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## Mangofish (Jun 12, 2019)

Well I kind of tore up the stock prop over Memorial Day trying to avoid the crowds and hit some low flats on the edge of a channel, so I ordered the BlackMax. I also ordered a PowerTech SRT3 9.5 x 9 pitch. When I'm running 2 in the LT 25 and livewell, it gets weighted and the 9" pitch will help with getting it on plane quicker. The overall diameter is .25" more as well. Once it arrives, i'll test it with the Garmin for speed and hole shots.
Overall the 20 Merc EFI and prop are great!


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## Stauter (Jan 20, 2012)

Duckboat said:


> I have a 2018 Merc 20,an it came with the black max 9.25x10,I didn’t have to order it,I’d have to say it’s the fastest aluminum prop
> 
> What size power tech? An I have mine bolted high on the transom too,I don’t know if that stainless would perform better for me...we got different boats....it could,but I’m afraid to waste money on one....but that black max prop is already cupped


It’s an 8” pitch with heavy cupping. But am bumping 6400 rpm. Getting it repitched to a 9.


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## Mangofish (Jun 12, 2019)

[email protected] said:


> It’s an 8” pitch with heavy cupping. But am bumping 6400 rpm. Getting it repitched to a 9.


yep, that's a pretty low pitch the 8. I believe the 9" pitch will rev up to the max of 6200 but I never run wide open, just ease up to a decent causing speed. I like the ability to jump on plane and get out of trouble quicker in waves with the LT 25. Avoiding the weekend warriors with large CC's that slow down to half which create even bigger waves then if they just buzz by me.


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## Duckboat (Apr 24, 2016)

[email protected] said:


> It’s an 8” pitch with heavy cupping. But am bumping 6400 rpm. Getting it repitched to a 9.


Oh ok so you have to go down in pitch when you go stainless,wich power tech model is that,an did it come with any cupping at all?


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## Stauter (Jan 20, 2012)

Duckboat said:


> Oh ok so you have to go down in pitch when you go stainless,wich power tech model is that,an did it come with any cupping at all?


Its a SRT. Has more blade area the the stock props or the SWA that PT also makes. None of the small outboard props come cupped. Because of the bigger blade area and less flex in a stainless prop you need to drop 1" in pitch to maintain approx. the same rpm. The performance difference is very noticeable with this prop. Only need cup if prop will not be running fully submerged.


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## Duckboat (Apr 24, 2016)

[email protected] said:


> Its a SRT. Has more blade area the the stock props or the SWA that PT also makes. None of the small outboard props come cupped. Because of the bigger blade area and less flex in a stainless prop you need to drop 1" in pitch to maintain approx. the same rpm. The performance difference is very noticeable with this prop. Only need cup if prop will not be running fully submerged.


Hmmm...well my mercury black max prop is cupped,wonder if it make a difference to have one cupped or not,when I’m full throttle down the lake the cavitation plates out of the water an i have spray coming up,does that mean it’s submerged or not


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## Stauter (Jan 20, 2012)

My black max aluminum is not cupped. Your cavitation/ventilation plate should be above the water when running for best performance. If set up correctly your plate should be even or up to 1” above the bottom of the boat. Any higher and you will need a cupped prop to reduce ventilation. 
I’m running the transport compression plate and with the heavy cup prop I’m able to run mine 4” above the bottom of my boat. (Top of tape is bottom of boat)


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## Duckboat (Apr 24, 2016)

[email protected] said:


> View attachment 78712
> View attachment 78714
> My black max aluminum is not cupped. Your cavitation/ventilation plate should be above the water when running for best performance. If set up correctly your plate should be even or up to 1” above the bottom of the boat. Any higher and you will need a cupped prop to reduce ventilation.
> I’m running the transport compression plate and with the heavy cup prop I’m able to run mine 4” above the bottom of my boat. (Top of tape is bottom of boat)


Oh I’m no where near the high,I’m probably one inch or a little over that’s it....but yes my black max is cupped,yours should of been too,what year is your Merc?


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## Stauter (Jan 20, 2012)

2019.


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## Duckboat (Apr 24, 2016)

[email protected] said:


> 2019.





[email protected] said:


> 2019.


Mines a 2018 ,should of had the same prop...you think that power tech is worth the money.


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## Stauter (Jan 20, 2012)

For sure. Been running them for years. Best small outboard prop on the market.


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## Duckboat (Apr 24, 2016)

[email protected] said:


> For sure. Been running them for years. Best small outboard prop on the market.


So I have a 10 pitch so then I’ll need the 9 srt an hopefully it doesn’t slow me down,I had a Suzuki df 20 before an tried running a stainless an didn’t have the torque to turn it....how much speed did you really gain with it?


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## Stauter (Jan 20, 2012)

Before I would try different props get you a tiny tach and confirm you are hitting your max rpm.


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## Duckboat (Apr 24, 2016)

[email protected] said:


> Before I would try different props get you a tiny tach and confirm you are hitting your max rpm.


Oh I have one ,I’m hitting it for sure


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## Stauter (Jan 20, 2012)

Then I think you will be pleased by going to a SRT3


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## Duckboat (Apr 24, 2016)

[email protected] said:


> Then I think you will be pleased by going to a SRT3


I’ll post some photos tomorrow of my set up an my prop now


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## Duckboat (Apr 24, 2016)

[email protected] said:


> Before I would try different props get you a tiny tach and confirm you are hitting your max rpm.


this is my mercury black max 9.25x 10...as you can see their is a cup already on it ,if you never tried one of these i bet you’d be surprised over the stainless in performance...an my plate is just a little above bottom...I called power tech an the guy told me the srt3 would lower my speed in a 9 an the swa3 doesn’t have a cup so it wouldnt bite as hard as my black max...our motors are not meant to run stainless


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## Stauter (Jan 20, 2012)

Looks like you have your motor positioned correctly in relation to the bottom of your boat. The prop picture is not depicting cup. Cup is positioned on the tip of the blade on the front or pushing side of the blade. Your picture is showing you were mercury tapers the blade to make the leading edge thiner. Not sure who you talked to at Powertech but I have been running the props on all size outboards for over 10 years. If your engines we not supposed to be running stainless props then Mercury would exclude their use from their warranty and its highly doubted Powertech, and other prop companies would be making them. There are two advantages to Aluminum props. Price and less likely to damage your lower unit when striking an object since the aluminum is softer material. Propped correctly the vast majority of boat owners will tell you than gained overall performance not just top end.


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## Duckboat (Apr 24, 2016)

[email protected] said:


> Looks like you have your motor positioned correctly in relation to the bottom of your boat. The prop picture is not depicting cup. Cup is positioned on the tip of the blade on the front or pushing side of the blade. Your picture is showing you were mercury tapers the blade to make the leading edge thiner. Not sure who you talked to at Powertech but I have been running the props on all size outboards for over 10 years. If your engines we not supposed to be running stainless props then Mercury would exclude their use from their warranty and its highly doubted Powertech, and other prop companies would be making them. There are two advantages to Aluminum props. Price and less likely to damage your lower unit when striking an object since the aluminum is softer material. Propped correctly the vast majority of boat owners will tell you than gained overall performance not just top end.


I’ll have to think about spending 225 dollars on a prop then,I don’t wanna spend it if it’s guna be a waste of money,I’ll wait till someone has the same set up with the same boat as me an then maybe I’ll buy it....you have a different boat


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## Stauter (Jan 20, 2012)

good decision.


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## Duckboat (Apr 24, 2016)

[email protected] said:


> good decision.


I honestly think that swa3 would be better for me than the srt3....pitch for pitch...but it’s will def lower my rpm so It May make me go slower


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## Stauter (Jan 20, 2012)

There’s more to prop than diameter and pitch that effect speed. The rake, blade style and surface area and finally prop slip.
Go run your boat and record your speed and rpm. Then go to https://www.mercuryracing.com/prop-slip-calculator/ and enter them along with your pitch and 1.85 for gear ratio. Click calculate for slip and see what you get. This will help you make a better decision on your next prop selection.


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## Duckboat (Apr 24, 2016)

[email protected] said:


> There’s more to prop than diameter and pitch that effect speed. The rake, blade style and surface area and finally prop slip.
> Go run your boat and record your speed and rpm. Then go to https://www.mercuryracing.com/prop-slip-calculator/ and enter them along with your pitch and 1.85 for gear ratio. Click calculate for slip and see what you get. This will help you make a better decision on your next prop selection.


It’s 2.15 gear ratio for my motor,says right on the website


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## Stauter (Jan 20, 2012)

Sorry you are correct use 2.15


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## Duckboat (Apr 24, 2016)

Ev


[email protected] said:


> Sorry you are correct use 2.15


everytime I entered something in an push calculate is says NAN


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## Stauter (Jan 20, 2012)

Works for me. I entered all values but slip and push calculate.


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## Mangofish (Jun 12, 2019)

prop calculator site i decided to buy a Tach. I'm going to set it up on my 2019 20 Merc, LT 25 and see what it tells me. Merc says I should be running a 11.5 or 12 pitch with my LT 25. They take the motor, 20 hp 4 stroke and weight configuration into their calculations.
These 20 and 25 - 4 stroke motors are designed (props pitched to 10) to be set up on heavier boats like the 14' and 16' utility jons which weigh 700 lbs empty not to mention adding people, motor and gear. so the props are under pitched for light lt 25's which the LT 25 falls under. I'll run the tach and report back then i'm planning on the Blkmax 9.25" dia and 11.5" pitch prop. it's 110 online. will report back on the results after that too. trial and error.


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## Duckboat (Apr 24, 2016)

Mangofish said:


> prop calculator site i decided to buy a Tach. I'm going to set it up on my 2019 20 Merc, LT 25 and see what it tells me. Merc says I should be running a 11.5 or 12 pitch with my LT 25. They take the motor, 20 hp 4 stroke and weight configuration into their calculations.
> These 20 and 25 - 4 stroke motors are designed (props pitched to 10) to be set up on heavier boats like the 14' and 16' utility jons which weigh 700 lbs empty not to mention adding people, motor and gear. so the props are under pitched for light lt 25's which the LT 25 falls under. I'll run the tach and report back then i'm planning on the Blkmax 9.25" dia and 11.5" pitch prop. it's 110 online. will report back on the results after that too. trial and error.


Well,i don’t have a LT 25 I have Lund Fury 1600, was out today an was running 6200-6300 at 24.3 on the gps,that’s me,fishing gear,full wood floor,rod compartments an full wood deck,3 gallon gas,the Merc weighs 127 with power tilt wich I have ,two light batteries an a trolling motor that all total together 67lbs,so without those I may get close to 25mph...boat weighs 520...if i went higher in pitch or went stainless I believe it would lower my rpm too much an I would loose speed,I think I’m at the top for this boat with the Merc prop


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