New prop suggestions needed. Should I go with the same one I have?

[enginesilo]

I have a 2005 Searay 180 Sport with the 3.0L Mercruiser and the Alpha 1 Gen 2 outdrive. I hit the edge of a sandbar and took a small chunk out of a prop blade so I want to get a new one and have the old one repaired and keep as a spare.

Eventually I may want to pull a tuber or a boarder, but for now I just cruise around. My boat is rated max RPM at 4400-4800 but i'm only getting around 4200 for whatever other reason.

Any other prop I should be considering for the benefits they bring? Definitely want to stay with an aluminum prop. Here is what Searay recommends:
Prop Size 14.25 x 21 AL
Max RPM's 4400-4800
Recommended Part #944868

3.0L MCM
Alpha 1 Gen 2 Outdrive
Ratio: 2.00:1

I've seen people on the boards recommend 19's instead of 21's, and also some recommend a 4 blade instead of a 3. Figure it would be nice to have a second prop that is better at doing certain things so I can then switch between them if ever needed.

Any recommendations? Or should I just go with another standard replacement blade of the same?

 

[SkiDad]

i would definitely go with the same brand prop but in 19 pitch

 

[enginesilo]

i would definitely go with the same brand prop but in 19 pitch

Thanks for the info. So when shopping for a 19 pitch, I see that it is a 14-1/2" instead of 14-1/4". Is that ok?

 

[SkiDad]

that's normal

 

[YoungMind]

Guessing you verified that you do in fact have the same as the recommended. If so, a 19P would be in order to get within the recommended RPM range.

As for water sports, depending on what exactly you plan on doing you might be better using a 17P for water sports so the engine does not get bogged down to badly. Although some of these guys use formulas that I don't know yet so they might suggest different, the 19P is a good place to start.

 

[dazk14]

What is your wot GPS speed? are you trimmed up until just prior to ventilation.

We have fitted many of the 3.0 liters, boats of similar size with a 4 blade ~14" x 19"pitch with great customer satisfaction. The $114 Amita at iboats is a good choice and value.

Properly tuned, your rig should be able to pull the aforementioned prop and provide for functional watersports.

 

[buckinrut25]

To give the most accurate answer, we need your max speed at 4200. This is helpful to calculate prop slip to see if you current one is doing a good job for you. Your going to want to confirm that your current prop is a 21P before you go any further. It does sound like your in need of a pitch reduction from your current one. If your at a 21p a drop to the same 19p will incease RPM to the safe range and improve hole shot while maintaining almost the same speed due to increased RPM.

 

[Starcraft5834]

current 21p likely to much prop,, drop down to 17 and look at a 4 blade.. Solas makes a fine prop. The 4 blade will overall be the best performer

 

[jestor68]

The 21 pitch most likely was original equipment and performed OK nine years ago when the motor was new.

It's time for a re pitch to get your rpm back up where it should be.

The 19 pitch 3 blade should help you gain 300-400 rpm. The diameter difference(14.5 vs 14.25) will have no measurable effect.

 

[enginesilo]

Thanks to everyone for all the knowledge, lots of great info going on right here.

So my boat is revving around 4000 RPM's, and does around 38MPH on the gauge speedo (Didn't have a gps handy) with the damaged prop blade, but even before I hit the bottom if was running around the same. It definitely used to run around 43mph and I'd say closer to 4400rpm's in the earlier years, not sure if its carb related or what not. It runs good otherwise so I've decided not to mess with it too much.

So for prop options, would the 4 blade ~14" x 19"pitch be a good choice?

I found someone local selling a used but good condition 14" X 19" Michigan Wheel brand prop I was considering buying just temporarily to throw on and use. Guy said he had it on an Alpha 1 gen 1 outdrive, any idea if that would align with an alpha 1 gen 2, or could the hub or spindles be different? Figure the used one would be a long shot but the guy doesn't want much for it, so it would be an easy fix while I shop for a nicer brand new one. This is the one he has, model 031025
http://www.propmd.com/michigan-wheel...ubber-hub.html

 

[enginesilo]

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