Prop size for 1992 OMC 454

[NoCal22Donzi]

I love my Donzi Classic 22 and currently have an aftermarket stainless prop with only 19 pitch. Stock 1992 OMC King Cobra 454. Would I be better off running 21, 23 or 25? My tach at WOT is 4600+, Looking for more top end speed now. Next year the procharger and some tweeking will take care of the rest. Anyone out there with a similar set up? What do you think would be my best bet for top end speed. Right now I'm a rather enimic 62 mph. Love to cruise the summer around 65. Next year 75+ :D but we need to take baby steps first! Thanks for the help!

Matt - Clearlake, Ca.

[oldLenny]

Drive ratio and altitude? 4600+, that RPM being what? What can you spin it to? Current prop? (design/manufacturer/ # blades and pitch)

62 mph, is that GPS or speedo, get a GPS reading or Radar. Two directions, same day...

This will create credible answers... :D

Welcome aboard from 1200 miles due North of you...Lenny

We need an acurate GPS and tach reading, I don't buy the 4600...nor the speed...something is out...or your drive ratio is very low...fill us in:)

Give us true RPM's, real GPS, and the rest will fall into place.

[NoCal22Donzi]

Lenny:

Thanks for the quick response. I have only owned the boat for less than a year so I am kind of new to all the technical aspects. My speed is via the stock speedo, but kind of verfied by running next two my seadoo 4-tech water crotch rocket. Which goes over 60. I am going to check it out with a GPS. I just figured that someone with the same stock ocnfiguration would have run into the same thing and would have an idea of the best prop set up. The prop was purchase from Overtons and it was their best Stainless 3 blade prop 19 pitch. The boat is at my weekend lake home so I can not remember the brand of the prop. The Tach hits 4600+ and even closer at times to 4800 RPM at WOT trimmed up. I am not sure of the info you need fromm the drive but it is a stock 1992 OMC king Cobra with a 454. I seems I have yet to see anyone with a big block on this board running a prop with only 19 pitch. Most seem 21, 23, or 25. I was hoping some of my other King Cobra OMC buddies could give me their ideas, props, pitch brands etc. Thanks for your help.

Matt in Clearlake, Ca.

[oldLenny]

They will... :D ...altitude?

[NoCal22Donzi]

Lenny:

Clearlake is appx. 1300 ft. above sea level. What does this have to do with prop size, etc?
Thanks!

Matt in Clearlake, Ca.

[oldLenny]

Altitude has an effect on horsepower and drive ratios. You don't make as much power the higher you go and high altitude motors run different jetting, higher prop ratios etc. 1300 feet doesn't seem like much. I was thinking about places like Tahoe and mountainous areas like that.

As Poodle said, at 4600 and a 19" pitch, you are not seeing 62...more like 58 and that is with NO slip. (you have slip...) Your tach might be way out and you are actually spinning towards 5200.

[NoCal22Donzi]

Lenny:

If what you say is stock 454 could be turning upwards of 5200 RPM. Still have a hard time seeing how a stock 454 is going to turn 5200RPM,, But if thats the case I need more pictch to get it down to the optimum 4400-4600 rpm level. seems to even layman if this is done I should see a few more MPH top end using one with say a 23 pitch. Ok now time to figure what 3 blade prop would wrk best with mt setup.
Thanks for eveyrones input! Matt form Clearlake Ca.
Thanks Again. Matt from Clearlake Ca.

[Eugene Nahemow]

Matt,
We crossed paths last weekend.
Did you see the Johnny Lang show?
If you need to use a GPS stop by my house and I will lend you mine.
There is the classic wood show up in Lakeport in the morning but I should be around in the afternoon. Shoot me an e-mail and I'll give you my P#.
Regards,
Eugene

[yorkey]

Hey there!

I just posted a similar question as I have the same boat and configuration as you! I'm in Southern California, you're in Northern California? You're only the 2nd west coast Donzi owner I've heard of so far.

I was just talking to one of these guys for advice on the same topic because I want to make sure I'm not pushing my 454 too hard for the same MPH I could get with a different prop at lower RPM's, obviously.

Let me know what you end up doing, I may just follow your lead. My mechanic says keep it down to 4400 RPM, so I want to make sure I can find my 65MPH at 4400 RPM's then! I have the stock speedo too, by the way.

Got any pics of your boat? yorkeystyl@hotmail.com