Prop Pitch?
 

I'm in need of a prop for a 1999 18' Mariah (I Don't know what model it is), 4.3 Mercruiser Alpha one. Does anyone have a suggestion as to what pitch would be correct for this boat?

Mike

Mike, I have a 4.3L with the alpha 1. I think the standard equipment is a 21p 14.25 in diameter prop. There are a lot of prop websites that will give you a selection of props for your motor and outdrive combos. Good luck and let us know your progress.

thanks for the info.

Yep, 14.25" x 21P - 3 blade aluminum is what they came standard with. A couple of us have changed over to 4 blade - 14.25" x 20p SS prop which essentially keeps your RPM's nearly the same and within the Mercruiser recommended range but provides just a little more "bite" at start and thru the mid-range. You may lose 1 - 2mph at top end though but i dont run there so dont really worry about it. There are a few here who run a 19P - 3blade also. The lower the pitch, the higher the prop rpm and the lower the top end but just ensure you stay within that 4400 - 4800rpm at WOT range.

Here's the link to Mercury's own prop selector tool:

http://sites.mercurymarine.com/porta..._schema=PORTAL

Was a 4.3L 160hp or 190 hp in 1999?

My brother-in law had a 1994 182 Barchetta with the 4.3L 2bbl and he ran a 21"x 14.25 Stilletto.

I have a 1995 180 Talari and I run a 19" x 14.25 Stilletto. Therefore, same hull, same motor, same prop except for pitch.

He could get just over 50 mph on his rig and I top out around 47 to 48mph @ 4900 rpm, just a hair over the limit. But I liked the acceleration of my rig much better.

My boat came with a 19P aluminum prop.

Paul's pretty much got the differences in those two pitches down spot on. The only other things i can think of are the differences between SS and aluminum affect prop performance and you can split that 19 - 21" difference by using a 4 blade prop at 20"pitch which should perform in the middle of those two but still get you that extra low end & mid-range oomph.
The '99 version of the 4.3 was 190hp as far as i know.

I run a 14.25 x 19P 3 blade black max prop on my boat and I get around 33-35mph speedo. I believe the rpms were around 4500-4700rpm range. I know I had posted up this info in some old posts somewhere on here, but im not about to go searching for it.... ROFL.

However, this summer I will be GPS clocking my boat! :wink_thumbup:

Just to clarify, my boat came with the standard 19p aluminum prop. I switched to a stainless steel Stilletto 14.25 x 19. My 4.3L Mercruiser is rated at 160hp.

The differences I noticed with the Stainless vs aluminum were:

1. Less prop blowout at higher trim angles.

2. More list to port due to prop torque. I believe the aluminum prop had a smaller diameter. This was a proplem at slower planing speeds and could be remedied by by trimming out the drive.

3. A slight increase in top end speed.

The best thing I ever did for my boat was add Smart Tabs. It accelerates like a inboard ski boat and rides like a 20 footer. :wink_thumbup:

That is really interesting Paul - thanks for that info. My SX18 had a list to port since I bought it, I have since fitted trim tabs to fix the problem.
You are right with the ride and acceleration, I get onto plane so quickly its amazing.
Cheers
Tony

Original Prop Pitch?
 

I have the 1994 z220 Talari - 350 alpha one - with original ugly old prop. I want to replace it with a pretty stainless prop, but don't know what pitch the original is (I like it's performance and don't want to get out a protractor, compass, and whatever else is needed to measure it).

Does anyone know what pitch I have (or an easy way to measure)?