18' 190hp bowrider nicked prop upgrade

[Blorton]

Hello All,

New to me boat with a couple of nicks in the prop so I want to get that swapped out. It's a three blade aluminum 14x23P and I'd like to try out a stainless. I'm on a large and deep freshwater lake with good charts so a bottom strike is remote.

1) Performance issue you are trying to correct.
Improved cruising speeds and top end. I'm open to 3 or 4 blade and am thinking something smaller than 23P would work better based on searching other posts here. Currently, when running flat out and tweaking trim, I get to around/just over 50mph on the gps. This prop does seem to ventilate a little too easily? This is on glassy water, btw.

2) Current prop manufacturer, model, aluminum or stainless as a minimum.
Mercury Black Max 14x23P - Aluminum

4) Wide open throttle RPM and speed with an average load (very helpful)
I will hook up an external tach before the next outing, but I believe it is not quite getting to 4k rpms currently. I run with a light load, one other adult most of the time.

5) Engine/drive make, model, year, and HP
Mercury 4.3 - 1998, 2bbl, 190hp

6) Boat make model, year, length and weight
Bayliner 185, 2003, 18', around 2100lbs

Any pointers/advice would be most appreciated!

 

[QBhoy]

Hi. I think you’re probably about 1000 rpm off on what your boat is actually getting in terms of rpms. It would be impossible to see that speed at 4000 rpm, I’d think.

 

[Blorton]

Thank you. I'm thinking you are right. The math doesn't make sense. I tried to hook up an old external inductive tach this morning but it's gone kaput. Have another on order and will try that one out.

 

[Sea Rider]

Check what's the min-max wot rpm range factory stated for that motor, go for a wot run as will usually be loaded and report max achieved rpm. Will know if in need to go for a less pitch prop to bump wot revs up and by how less pitch number...

Happy Boatiing​

 

[jimmbo]

What is the Gear Ratio of the Outdrive?

 

[Blorton]

1.81

I went ahead and ordered a stainless 3 blade TP of the same size and pitch as what’s on the boat. I used several online sizing tools and that’s what they all came back with. So I’ll see how that one does and maybe get the four blade later for watersports.

 

[velociraptorfarmer]

I have that exact same engine in a similar boat, same 1.81 gears as well. Only difference is I've got a Sea Ray that's about 600lbs heavier.

I've got a 14x21p 3 blade stainless prop on mine right now that needs to be tested, but should be about the sweet spot.

In the past I've run a 14x23p 3 blade stainless that topped out at 4500rpm@48mph with just me in it, a 14x20 4 blade aluminum (4900@46mph), a 14x19p 3 blade aluminum (waaaay underpropped), and a 14x21p Turning Point Hustler 4 blade aluminum prop (4300@48mph). Ignore the hustler, they act like a prop that's 2" up in pitch from what they say they are.

Verify your WOT RPM with a known good tach first, but I'm guessing you're going to be around a 14x21p 3 blade in stainless.

 

[JimS123]

Mercury marine's online prop selector guide is an awesome app to help dial in your needs. They will offer options re. SS or aluminum.

BoatTest.com also provides excellent data on certain models. Check them out - they might just have your very boat on file.