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View Full Version : 4 Blade Prop for 28ZX 383 Re-Power?



ROADTOYS
03-06-2012, 05:25 PM
What 4 blade prop do you recomend for 350hp 383 MPI strokers on my ZX28? I have herd 4 blades are more stable and come out of the hole better, my 3 blade Mirage props didnt seem to plane worth a crap and would cavatate bad trying to plane out with the old 260hp, then again, I want to keep the top end also.....am I dreaming???

Mckillop
03-06-2012, 06:07 PM
What was the pitch on the MP's ypu were running? What was you WOT RPM with those props and the old engines?

ROADTOYS
03-06-2012, 06:26 PM
Not sure on the Mirage's pitch, I just bought it a couple of months ago, it was runing around 5,000 to 5100, I think the 383's can run up to 5400 or a little more, are all of the set ups different for the stock 350MPI 260hp? I am sure the props are whatever Donzi used in 2000 on the ZX28's

Conquistador_del_mar
03-06-2012, 07:20 PM
I would highly recommend the Revolution 4. I tried a few different props on my 25' Martini and it really does well overall with the Revolution 4. Bill

Ghost
03-06-2012, 07:33 PM
Roadtoys, I *think* Donzi tried out different props because there have been planing issues. I'm not at all convinced there was necessarily a "standard, right answer" for any year. Maybe, but I suspect it's more fluid and worth reading the stamp on your props and your drive gearing to kick it around.

There are some discussions about methods people have used to get the boats on plane. If you use advanced search, "VetteLT193" and "FISHINSUCKS" are two board members who've talked about it. Maybe something here will help:

http://www.donzi.net/forums/showthread.php?58217-28-ZX-planing&highlight=tabs%2C+throttle%2C+plane%2C+cavitation

flying tomato
03-06-2012, 07:43 PM
Are you serious? You own a Donzi performace boat and don't even know what pitch prop it has on it and are looking for help? That is funny!!

In the red
03-06-2012, 08:28 PM
[ QUOTE=$originalposter]{$pagetext}[/QUOTE]

It depends on the drive ratio you have. Most 28 ZX's with 350 Mag MPI's (300hp) came with 1.5 drives. Mine for some reason came with 1.65's and 3 blade mirage plus 25's. They were hard to plane but very efficient at cruise speed. I have tested bravo I 4 blades and hydromotive 4 blades and have found that a set of labbed 26p bravo I's are the best top end and out of the hole props for my boat. Mine runs 5250 rpm's with two people and 70mph. It comes out of the hole hard if pushed without prop slip. I sent them off to BBlades this winter to have them cleaned up and work their magic hoping for a few more mph. We will see..............

FISHIN SUCKS
03-06-2012, 10:50 PM
the standard prop setup for the twin 350mag/300hp with a bravo 1 1.5 gear ratio is 23P Mirage + (the + gets you the bow lift you need for the 28ZX hull). Not sure if the 260hp had a different gear ratio or prop.

ROADTOYS
03-07-2012, 07:52 AM
Thats exactly what I was looking for, thank you, I bought this boat to re-power it, the engines were my main concern, now we move to the props.

FISHIN SUCKS
03-07-2012, 08:37 PM
Happy to be of help my ZX Brethren.

pipnit
03-08-2012, 07:11 PM
this might help: http://www.rbbi.com/folders/prop/propcalc.htm

VetteLT193
03-12-2012, 12:27 PM
The drive ratio seems to make a big difference.

Through a lot of backwards research I think Donzi did their testing with 1.5 drive boats. I know for a fact they went aggressive as they could on the X dimension.

The kicker is details. At some point Merc suggested the default gear ratio for 6.2 MPI boats (320 HP) be 1.65 (this is odd because for the 350 Mag the sea level ratio is 1.5 and the high altitude ratio is 1.65 which makes more sense).

The result of the 1.65 drive is you get a bigger pitch prop (2 inches more pitch)... mathematically this works out as a wash, you should run the same top speed and cruising speed. The detail here though is the diameter of the props goes down as pitch goes up. The small difference in diameter seems to be just enough to throw a giant wrinkle in things.

With all that said be wary of prop suggestions without knowing the drive ratios. My 28 (with 1.65 ratio) hates the living crap out of M+'s. they suck getting on plane in calm water and it's a battle in rough water. The cruise isn't that good either. The only thing that is good with M+'s is top end. You'll notice the same complaint from basically every 28 ZX owner that has 1.65 drives. I now run stock B1 26 pitch and the cruise is fantastic. The top end is slower than 25 M+'s. planing is no problem under any conditions, handling is great too (one M+ would blow out in turns)

The same is not true for the 1.5 ratio guys. Fishin Sucks, Trueser (sp.?) and others with the M+ mounted to 1.5 drives don't have the same problems and if you are in that category I would take advice from them first.

The Hedgehog
03-15-2012, 06:41 PM
I heard that it is best to run one Mirage and one Mirage Plus. If you can trim it just right and get the disco lights in sync with the stereo, you will get a few extra mph.

FISHIN SUCKS
03-19-2012, 06:57 AM
[ QUOTE=$originalposter]{$pagetext}[/QUOTE]

confirmed

roadtrip se
03-19-2012, 12:54 PM
because it looks nuts here, but Hedge is absolutely spot on. Wouldn't believe it, if I hadn't seen it for myself. Must be the wattage regulator weight for the amps, lights, and the disco ball..

Z-Man
03-19-2012, 05:29 PM
Send me an IM as I'm in the middle of prop testing on 4 blades for my repowered 28 ZX. The 24 fusion will carry the boat nicely or a rev will too. You want high rake or all blank breaks loose. Trust me. Dre