[brett weber]

sorry i have not been on the site for a long time just busy. just wondering if any one with the same motor 4.3 v6lx 4bbl 205hp runs a 19 pitch ss prop. was running a 22 pitch but wanted more punch. so i just bought the 19. just wondering if the 19 was going to make the rpms to high.

[WetWilly]

Hi Brett,

When you were running the 22 pitch prop, do you recall your WOT rpm? Acording to Mercruiser, the 4.3L should be in the 4400-4800 rpm range at wide open throttle.

Rule of thumb, a change of one inch of pitch equates to a rise or drop of about 200 rpm. This does not include "cupped" props, as they can drop 200 rpm over a "non cupped" prop of the same pitch (cupping is equivalent to 1" of increased pitch).

So the change from 22 to 19 should be a rise of about 600 rpm at any given throttle position so be careful the first time you crack the throttle wide open with the 19 pitch prop until you see what your new WOT rpm is. As long as your within the 4400 - 4800 rpm range your ok, otherwise, you have to pay more attention when you run the throttle flat out to prevent over revving your motor.

Although this article is from another boat manufacturer, it explains many prop features in an easy to understand (plain English) format. See here.

Hoped this helped,
WetWilly

[mikeyt]

hi Brett

Willy's info is spot-on and yep, pretty good chance that your revs will jump considerably. I run a 21" aluminum 3 blade on mine and i hit 4800 rpm & 50mph on the speedo. I wanted a little more low end 'punch' so i did a fair bit of investigating and decided to go with a 20" - 4 blade SS prop for this year which should (at most) drop my revs by 100 - 150 rpm and give me better acceleration as well as some additional mid range oomph. I might lose 1 - 2 mph on top end but i rarely travel at that speed anyway and i stay within the recommended rpm range. Going from a 22" to a 19" may be too much....so better watch the rpms!

[brett weber]

thanks for the info. most of the lakes i run are not big enough to get full speed on your rig. probably running 35/45 mph most of the time, and if i go to a bigger lake that i want to hammer down i can put the 22 back on. thanks alot boating season is almost here, stay safe.

[KSP181]

Hi Brett, I have the same boat. Mine has a 4.3L 2bbl. It has a 21p 13.25 in. prop. At WOT it is over the 4800 rpm limit. I am going to change to a 14.25 in. prop and stick with the 21p.