[cleah]

I have a 1993 2350Z with Merc 454 and Bravo 1. I run it in a lake at about 5 100 ft altitude. It has a 4-blade stainless 15.25" dia. 15" pitch prop with lots of wear and dings. The "don't exceed" engine rpm figure is 4800. However, it will easily exceed this if allowed to once on the plane. I am thinking of swapping out the prop for one in a better condition. Should i also be looking to increase pitch, and if so, what to.

Any suggestions welcome.

Clive

[WetWilly]

Hi cleah,

Can you provide some more info?

What is your RPM at WOT?
What gear ratio is your Bravo 1?
Lastly, what type of performance are you looking for (Over all, Hole shot, Mid range or Top end)?

FYI - at Wide Open Throttle RPM, each increase in prop pitch reduces RPM levels by roughly 200 rpm's per inch of pitch.

WetWilly

[cleah]

I haven't tried WOT as worried about engine damage. The never exceed rpm in the book is 4800. It is easy to exceed this before planing and very easy after. I have to throttle way back to limit to 4800 rpm on the plane. My main aim is torque. I have 4 adult sons who would like to ski and tube together. I need a good skiing top end speed, say 40 kt, reasonable out of the hole, fairly quick time to plane, and most of all load pulloing power.

I am fairly new to boating, but have read a lot about props and worked on aircraft props for several years. It would appear to me that my 15.25" dia. 15" pitch, 4-blade SS with leading edge erosion and dings is not up to the job and may not have been the correwct prop for the boat when I bought the boat. I think I am probably looking for a 15.25" dia. x 19" pitch 4-blade SS.

Any advice, or whereabouts of a good used unit is welcome.

Clive

[WetWilly]

Hello Clive,

I assume you meant Kilometers per hour (40 Kph = 25 Mph) and not Knots (40 Kts = 46 Mph) for your skiing speed... We normally ski at around 32mph and low 20's for wake boarding and tubing.

Going to a 19p from a 15P will definitely bring the RPM down a bit, about 600-800 RPM at WOT (every 2" increase of pitch results in about a 400 RPM reduction at WOT), so if your current WOT RPM is around 5600, a 19P should get you near the 4800 Mercruiser recommends.

WetWilly