which backup aluminum prop should I buy?

[trout74]

I have a 24ft. Manitou tripple tube pontoon boat with a Mercury 150 Optimax Pro XS. I have a 15pitch Enertia prop on order. I want to have an Aluminum prop for a back up. What prop should I buy and what pitch should i buy for a backup? Thinking Black Max 15 or 16 or 17 pitch? what are your thoughts?

Thank you!

Trout

 

[MikDee]

What's on there now?

 

[trout74]

Currently I have a 15 pitch Mirage Plus ( and its the wrong prop, hence the Enertia on order) My Current Max PRM's is 5000 with the Mirage, so I ordered Enertia to hopefully fix that. But I want an aluminum backup in case of emergency.

Thanks,
Trout

 

[trout74]

nobody has a suggestion?

 

[MikDee]

If you can spin that 15" Mirage to 5k, I would say a 17" pitch Black Max should work fine!

 

[bruceb58]

If you can spin that 15" Mirage to 5k, I would say a 17" pitch Black Max should work fine!

Why would you say that when the suggested WOT RPM is 5000 to 5750?

 

[MikDee]

Why would you say that when the suggested WOT RPM is 5000 to 5750?

Normally when going from an Alum. to SS prop, you drop down a pitch size usually 2 increments, so vice versa when going back to aluminum. Plus, Have you seen a Mirage prop? (I have) It is pretty big, with good size blades, & heavy as it is. IMO,The Black Max in 15" pitch being smaller, & lighter, may overrev,, whereas the 17" pitch should actually pick up a few rpm's and be just right.

 

[KYsean]

Sounds like the OP needs to go to a 13 Pitch. That 15 is lugging the engine if they are only getting 5000rpm.

 

[trout74]

Sounds like the OP needs to go to a 13 Pitch. That 15 is lugging the engine if they are only getting 5000rpm.

I agree I need more RPM's, that is why I have an Enertia on order, it should give me more RPM's, that is my hope at least!

Thanks for the suggestions, I think ill get a 17" Black Max.

Trout

 

[bruceb58]

You again, huh Bruce? Normally when going from an Alum. to SS prop, you drop down a pitch size usually 2 increments, so vice versa when going back to aluminum.

And you keep on saying this wrong information. With an identical shaped prop of the same pitch, when you switch from alum to SS, the SS will have slightly higher RPMs.

 

[bruceb58]

OP...do yourself a big favor and go to the mercury prop selector page:
http://www.mercurymarine.com/propellers/prop-selector/#

I plugged in your motor and a 24' pontoon, You can go in and put in your exact weight:
Here is what I got for you and I think I am low on the weight. You see a 17" prop recommended?

 

[trout74]

And you keep on saying this wrong information. With an identical shaped prop of the same pitch, when you switch from alum to SS, the SS will have slightly higher RPMs.

So your suggesting I gets 15" aluminum, over 17"? My hope is that whatever I get can pull 5500-5700 RPM's at WOT with about 5 people on board. I do think a 15" Black Max would spin much faster than the mirage Plus, it is a huge prop, and heavy.

thanks,

 

[bruceb58]

Wait until you get your new prop on there and see how it works. When you do your test run, make sure your gas tank is full and have a few people go with you to simulate your normal load.

The weight of the prop means basically nothing. It's the shape of the prop that matters.

Kinda interesting that it suggest a 14" in the Inertia and 12" and 13" in the Black Max. Kind of backwards from what MikDee is telling you. But what does Mercury know!

 

[trout74]

Thanks Bruce. I have been to that page before. Those props seem small to me, BUT I am not a prop guru and I most certainly could be wrong. I think ill do as you say, problem is, my enertia is not scheduled to be at my house till August 1st. And I want to put on something other than my current Mirage Plus for this weekend, and I have a Dealer that can sell me any aluminum prop I want now. So I was trying to get something that I can use till the Enertia comes, that will be better than 5000 RPM's with the Mirage. Actually loaded, the Mirage only gives me 4800 RPMs. 31.9 MPH per GPS loaded as well. Manitou, the manufacturer says I should try to 15 Enertia, and should be at 35-36 MPH. Was hoping to get there with an aluminum for the next two weeks. Sorry for the long rant.

Thanks for your time!

 

[bruceb58]

The page was dead on correct for my pontoon.

Does the dealer have a loaner prop that you can try?

 

[trout74]

The page was dead on correct for my pontoon.

Does the dealer have a loaner prop that you can try?

Good question, ill ask them tomorrow when I go to talk to them. I don't really trust dealers too much, that is why I'm asking in here first before I go there. So if I get a 13" black max and it spins at say 5700 RPMs do you think I will go faster than my 15" mirage at 4800-5000 RPM's ?

 

[MikDee]

The link don't work Bruce,,, Anyway, the Mirage prop is 16" diam., and the Black max is only 14" diam.

 

[trout74]

When I go to the prop selector page and use the RPM and current top speed and current prop size as my final inputs, under " details" is says calculated pitch, 12.7. What is the " calculated pitch" ? and why is it different than the suggestions listed below. It does the same thing in your post, lists a calculated pitch and then suggests another.

Thanks

 

[bruceb58]

The link don't work Bruce,,, Anyway, the Mirage prop is 16" diam., and the Black max is only 14" diam.

Link works for me. Black Max is 16" diameter for the ones suggested for his boat/engine.

 

[bruceb58]

When I go to the prop selector page and use the RPM and current top speed and current prop size as my final inputs, under " details" is says calculated pitch, 12.7. What is the " calculated pitch" ? and why is it different than the suggestions listed below. It does the same thing in your post, lists a calculated pitch and then suggests another.

Thanks

Calculated pitch is the theoretical pitch you would get to reach your WOT RPM. Obviously, there isn't going to be that size available so you either round up or down to the closest integer size.

Just realize that the speed may not be accurate because it is for a generic pontoon boat. You have a tritoon and possibly have lifting strakes, etc.