prop for merc 4.3 Alpha 1
 

I am so glad to be apart of your community I have a 2006 SX19 that I love. I currently have a 14 x 23 prop which currently does
not perform as I would like when I have more than 4 peopl or am trying to pull a towable. I would be interested to hear any advice on the prop I should get for my boat. Thank you for aany direction you can provide I am considering a 21 and 19 pitch. Before you ask the WTO is 4200.

Re: prop for merc 4.3 Alpha 1
 

First off i would suggest that you read the 'sticky' at the top of this forum & educate yourself on prop selection. Its not rocket science and most of the links in the sticky can give you a basic understanding of selecting a prop for your boat.

Second, yours is a pretty common question here. Bottom line is that your engine has a recommended WOT range of 4400-4800 and its clear that you are below that range. As a result your engine is working much harder than it should to get your boat moving & to maintain speed. So the solution is fairly simple & you have identified that you need to reduce the pitch of your prop to get better performance. As a general guidance, for every 1" drop in pitch you will get a corresponding 200 (give or take up to50) increase in your WOT rpms. You need to get yours up into the 4600 - 4800 range where the engine & prop combination operates most efficiently. A 19" 3 blade prop should have you right around 4950rpms and a 21" around 4600. Being slightly over your recommended range wont hurt as long as you dont run the boat at WOT for any length of time. Running at WOT for any length of time causes excessive wear & tear on your mechanicals and is a fuel waster.

Most members here run a 19" 3 blade. Some of us run a 20" - 4 blade (extra blade = extra bite), there are a few here that run a 21" 3 blade (used mostly for cruising) and if i remember right one person here runs a 23" (but he's a bit odd :) ). I would suggest that if you use your boat for pulling tubes/wakeboarders/skiiers or generally have 4 or more adults in it, that you consider using a 19" - 3 blade or a 20" - 4 blade.

The following are general rules of thumb:
Lower pitch = faster holeshot, better planing ability, increased rpms, lower top speed.
Higher pitch = slower holeshot, slower planing ability, lower rpms, faster top speed.
3 blades are generally the most efficient props. 4 blades provide extra bite but cause extra drag which usually results in a slightly lower top speed when compared with the same pitch 3 blade.
Cupped blades provide extra bite & reduce ventilation as well as allowing you to trim up just a bit more. They also reduce the effect of pitch change.
Aluminum is the least expensive prop material for general use and provides good performance.
SS props costs more but usually provides slightly better performance.
Composite props (IMHO) are good for spare "get me home" props only.

There is also another option which helps with planing ability and improved low speed control and that involves the installation of a pair of Smart Tabs. Many of our members here with 18-22' boats have installed them (me included) and are very happy with the additional benefits they provide. Cost is usually just under $150, installation takes about 30 - 45 mins and its DIY. You can do a site search for Smart Tabs or read about them/watch the video here at the Nauticus website. If interested, your boat will use the Smart Tabs SX version with the 60# actuator arms.

Re: prop for merc 4.3 Alpha 1
 

Sounds like I should go with 19 pitch for general use. What top end speed should I expect with a 19 pitch? Thanks!

Re: prop for merc 4.3 Alpha 1
 

A 19" pitch 3 blade should have you around 47-48mph. A 20" 4 blade about the same and a 21" - 3blade "should" hit 49-50 but your holeshot & midrange response wont be near as good as the 19 or 20.

Re: prop for merc 4.3 Alpha 1
 

I was looking through the links from the sticky you posted. The recommended prop on the mercruiser prop guide for this boat and my boat shows up as a 13.25" 25 pitch 3 blade prop. If I go with the 19" 3 blade, what pitch would I want to get? (Ski boat) Do you have any recommendations on who to order a prop through?

Re: prop for merc 4.3 Alpha 1
 

Good response miket

Re: prop for merc 4.3 Alpha 1
 

Mikeyt is right on the money as usual, 60 pound smart tabs are easy to install and really make a huge difference,
If you are down in the states i recommend calling joe at hill marine, they are the go to prop company, knowledgable and priced well, read the customer reviews! Doesn't hurt to call them/ emailThey have an exchange policy that lets you tey the props, if you don't like you cans switch to a different pitch. Just tell them the size, rough weight, your wot rpm and what you want to do with your boat.


Sent from my iPhone using Tapatalk

Re: prop for merc 4.3 Alpha 1
 

19" is the pitch. The diameter will be approximately 14.25". I'm not sure what boat you have but most 18'-20' Mariahs with the 4.3, 5.0 and 5.7 run very well with a 19" 3 blade or a 20" 4 blade. The 4 blade makes it better for pulling wakeboards / skiiers to and if you combine that with a set of Smart Tabs it doesn't get much better than that.

Re: prop for merc 4.3 Alpha 1
 

Lol! 23 pitch i wonder who that is? Same guy who's boat doesn't like water? [emoji12]


1998 shabah 180
5.7l 350 mag
Bravo III

Re: prop for merc 4.3 Alpha 1
 

no, i cant remember who it was now cuz it was about 3-4 yrs ago when he said he ran a 23" on his 180 with a 4.3 and that prop gave him great acceleration out of the hole and he could hit 52mph at the same time. Someone must have changed the markings on that prop as a joke and swapped out his 4.3 for a 5.7 when he wasn't looking... :yes_grin: