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Superhilti
08-23-2007, 08:31 PM
I have a 2001 Donzi 22ZX and had some problems with the lower unit. While in the shop the mechanic noticed the boat had a 24p Bravo prop. He told me this was too big for the boat. Can someone please let me know what the appropriate prop would be. It has a 300hp 350 in it with a new alpha outdrive. Any help would be appreciated.

Superhilti
08-25-2007, 07:34 AM
Any Idea?

DonCig
08-25-2007, 07:38 AM
We need to know the drive ratio in the stern drive unit to answer the question. Is it a 1:65. or 1:50. or 1:36 final drive ratio?
Sometimes you can find a sticker or a stamping on the outside of the sterdrive housing that will answer this question.
There are other ratios besides these, but these are the ones that I am used to dealing with.

Don

BigGrizzly
08-25-2007, 09:30 AM
What are your max RPMs. Mark Laslo spins a 24 bravo with his 22ZX, I think he has a 350 Mag in his.

Sam
08-25-2007, 09:32 AM
Unless he has first hand experience with the boat in all conditions :confused:, he needs to re think his advise, here's what you need to do.

First find out what the recommended RPM range of the boat is. Then run the boat and establish a base line of rpm,s that corresponds with your recorded GPS speed. If possible do this in various water conditions, I know this may be difficult. Based on the recommended RPM range you can determine pretty quickly if you are proped right.

So if your RPM range is 4600 - 4800 and you are turning 4400 you will need to go down an inch or so resulting in an RPM increase. If you are turning over the recommended rpm range you will need to go up in pitch lowering your RPM's. Make sure that when you do your testing that you find a nominal position for your trim angle when you record your numbers.

Where in Mich are you located ?

Sam

BigGrizzly
08-25-2007, 09:35 AM
All 24 pitch props are not created equal. Typically a 24 /bravo relates to a 23 Turbo.

Superhilti
08-25-2007, 12:46 PM
Sam I'm in Algonac on Lake St. Clair. I've just had the upper housing replaced on the boat I had an incident a couple weeks back where the gears just shredded. I bumped something in a canal and after getting to the river I got up on plane then all hell broke lose. When I took the boat to the marina and the mechanic took it apart he felt it was the wrong gear ratio so he investigated further and found that is was not the same as the one that was on when it left the factory. So he replaced it with the one mercrusier said went with it. He also thinks the Bravo 24p prop is the wrong prop. I think I'm gonna have him put that prop back on and see where I'm running. He has a used three blade 19p prop he would sell me but I'm thinking that is too small.

MOP
08-25-2007, 01:01 PM
Got a SB Z out this way, it is a 1.5 with a 21 Mirage turning 4900. My guess is you will be very close to that range.

Phil

Sam
08-25-2007, 04:14 PM
Send me a PM so we can get together, I'm on Harsens Island :boat:.


Sam