[lowerthanu]

Hey guys,

I have a 92 Mariah Z240 with the 454 and Bravo 1. I have been looking around and am trying to find out what the stock prop for this boat was?

I just bought it the end of last season and it seems like it it under propped for what I do. Currently it has a 3 blade stainless Mirage 19 pitch on it. It gets on plane very very quickly but does not seem to work the engine at all on the mid to top end. I only use the boat for running the river and am looking for the best perfromance in the mid to top end. Any suggestions on what prop pitch and size would be best?

Thanks for any insights!!

[WetWilly]

Hi lowerthanu and welcome to the club!

Can you tell us what your RPM is at WOT? For overall usage, the prop's pitch and diameter should have you running between 4200 - 4600 RPM at WOT.

The general rule of thumb is about a 200 RPM drop with every 1 inch increase in pitch. (ie. going from a 19P to a 21p will drop about 400RPM at WOT)

WetWilly

[lowerthanu]

Well I finally got the boat out this weekend to test it out, and with 6 people on board, I would rev to 5200 on the top end. Would you think a 21p would be in the bes of should I give a 23p a try?

[mikeyt]

Originally Posted by lowerthanu

Well I finally got the boat out this weekend to test it out, and with 6 people on board, I would rev to 5200 on the top end. Would you think a 21p would be in the bes of should I give a 23p a try?

WetWilly's got you going down the right path but I think you will find your boat will be a bit 'lazy', particularly in the low/mid range acceleration, with a 23p on it although it may be that the big 454 can handle it. If you are at 5200rpm at WOT with the 19" then a 21"p will have you close to 4750-4800 which i realize is slightly more than the recommended range but should still give you good acceleration and add 2-3mph on to your top speed. Another option would be a 22" 4 blade or even a 5 blade ( like a 'High 5') which should have you right around the 4650-4700 rpm, give the added 'bite' of the extra blade and still give you 2-3mph extra/

I find that while top speed is nice to have, solid mid-range acceleration really makes a difference in the feel & performance of your boat.