13 pitch or 15 pitch for Mercury 50hp command thrust

[biologicole]

I hit a stump with my 2017 Mercury four stroke command thrust and busted my prop. I used a chart selector and ordered a mercury black max prop to replace it. While installing it yesterday I noticed that it was a 15 pitch. The prop I’m replacing was a 13 pitch. I’ve read the internet until I’m now confused as to how this will effect my boat. The boat is a 2017 Lund 1675 with outboard tiller and I don’t know what the rpm’s were with the old prop.

Can someone please tell me in simple terms if I can actually use this prop safely without damaging my motor? What differences will I see in performance?

The black max is a $200 prop And I don’t want to just go run it for a while and harm my motor or discover that I need to spend another $200 and get a 13 pitch prop.

Thanks

 

[Sea Rider]

It's imperative to tach to know the max wot rpm achieved with previous installed prop to know if performed so-so, good or excellent powering your boat as usually loaded to go for exact same or one with a less pitch to pull wot revs if needed. Is it possible to change it for a 13 pitch as previous installed one ? How loaded, number of souls on board do you plan to go boating with ?

Happy Boating

 

[biologicole]

Yes, I believe I can exchange the prop for a 13 but it will take a couple weeks to ship back and forth. Normally there will be 2-3 on board but occasionally 4. Now that I know more I really wish I had paid more attention to that tach.

 

[WesNewell]

Go to the mercury prop selector and find what pitch you want. A lower pitch will provide a better hole shot.
https://www.mercurymarine.com/en/us/propellers/selector/#!/step-one

 

[Sea Rider]

To dial the right prop for your Lund/Merc 50 combo would recommend to install an induction Hardline hour/tach model : HR-8062-2. Once installed tach current 15 pitch prop with 2 and 4 up and write down how much wot rpm each individual test achieved. Ideal would be for motor to wot rev at least 5500 rpm with 4 up which is the middle wot rpm range factory stated.

With 2 up the wot rpm will increase towards its max 6000 wot rpm range depending on how light, medium light or heavy champs happen to be the extra 2 boaters.

Is it posible to water test that 15 prop and if found not suitable change it for a new 13 pitch ? It's a night day boating experience taching any motor with a real tach than by ear sound. Can install the tach closer to the tiller grip to read it at distance along checking run hours.

Happy Boating

 

[WesNewell]

you might also want to remove the air intake restricter to boost your hp upwards of 60 hp. Item 21 in this.

 

[biologicole]

Thanks for the responses. There is a tach on the boat and the recommended wot is 2500-300 rpm. The Mercury website prop selector says 15. Also, it’s a 60hp not a 50. Clumsy fingers. I think I’m going to run the 15 as it looks like the right prop.

 

[WesNewell]

I've also got a 2017 merc 60 hp 4s and rpm range is 5000-6000 on mine. It's not a CT but I don't think that means anything as far as rpm range. But being a CT means your gr is 2.33 compared to 1.83 of the standard engine. I'm not sure why they would put a CT on your boat but in any case it will require a higher pitch than the standard engine to achieve the same speed. I run a 14p on mine. that's the equivalent of an 18p on yours, so unless you boat weighs more than my 1000# by a considerable margin I'd say a 15P for yours should work fine. Still, if I were you, I'd consult the mercury prop selector to get a better idea of the pitch you want.

 

[Sea Rider]

The recommended wot is 2500-300 rpm ? there's no motor that will rev that low under wot, not even overly pitched..

The prop the Prop Selector recommends it's a starter one from where to go from, lots of variables to have into account that could make that 15 prop from being an ideal one for your current application, only a wot test as loaded on flat calm water cond will indicate if the motors revs happily between at least middle to its max wot rpm range whichever rpm range you prefer.

If both 50 and 60 HP motors share the same exact CC powerhead, removing the air intake restrictor won't give a 10 HP + increase. If so all boaters will buy a 50 HP, remove the air restriction and save lots of cash, there's a price difference to pay between both mentioned HP motors A Matter to check the time advance, carbs, inyectors, ECU specs whatever part will need to be changed for a correct HP upgrade to a extra cost.

Happy Boating

 

[WesNewell]

One correction to my post. rpm range is 5500-6000, not 5000-6000. I stand by the rest of it, including the air restricter to improve HP of 50 hp engines, and 40 hp engines with the same 995cc block for that matter. This will be especially true at higher altitudes.