Offshoreonly.com - Prop help on a Donzi 28zx.

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I've got an '05, before I added boost it ran almost identical to yours for speed but about 100 rpms more. I was using 23 mirage plus'. It's not an exact comparison now but I've tried 27 mirage+'s and 26 B1's, the three blade is a bit quicker and more stable, but slips a lot out of the hole. The 26 B1 is the best all around, accelerates hard out of the hole no matter what the load and is worth the loss of a couple mph up top in my opinion. Either way Brett and the guys will sort you out!

i think 22p B1, or a 24B1's

but the boat haas alot of rpm now, so i think the 24 may be they thing to try first.

Quote:

Originally Posted by mittens (Post 3399617)

Ok been playing with a donzi 28 ZX, has 350 mags, bravo ones, with meriage 23p on it.

odd thing about it, when coming out of the hole it will blow the props out easily, so you really have to baby it until she is on plane...... but yet my single 454mag with same drive, and same prop will not blow out? guessing has to do with the boats differnt x demention, step hull, or something?

anyway thinking he should step uop the prop to get it hooked in better. maybe a 22-24p, 4 blades?

thoughts?

I have the same boat your numbers are dead on with the 23... i have 23 m+ little work. mine doesnt blow out but the old 25 m i tired did wasnt +'s. ran a little faster at 3300-3500 23 47mph-49mph, 25's 50-51mph. 5000 23's 70.3 25's 4800 71.8 yea by the way it doesnt like 4 blades 22 or 24 bad really bad.. 62-64 maybe 65 tops... sucks....bad

Quote:

Originally Posted by A.O. Razor (Post 3400411)

Do you know your x-dim?

Do you have 1.36 gears in the drives?

It does look like you need 4 blades. If the 23 puts you @ 5000 rpm, I would try B1's in 22" or Rev4's in 21". Another way, is to try Mirage+'s in 23". It has more cup and bite harder than the old Mirage. If the M+ works, it'll prolly be the fastest of the lot.

One last thing. If you have 1.5 gears. Something's not adding up. To go 70 moh @ 5000 with 23"'s you'll need a slip of 4%, and that just seems wrong. When running 66 mph it's 9%, still low, but possible. What I'm getting at is, if you might have a tach or gps issue? If you run a 1.36 gear, your slip is 13% and 18% which seems more correct, given that it sounds like your prop's need more blades or cup.

I was told the same thing about the slip% dont get it? i had two gps read the same numbers...?

Well i am going to try and catch brett on the phone this week and see about trying some different options.I was thinking some 24 p 4 blades made since but if you can only get 65 out of them maybe its worth it to just keep what i have and baby it out of the hole.

It did suck this weekend though doing the poker run with a full tank and a cockpit full. Until i was running wide open that is ;)

Mine has the 6.2's (377's) with 1.65 ratio drives. With the 25 Mirage plus it runs ok. If it is rough, hard to get on plane. calm water planing only half way sucks. I tried the 23's, they were too small... blow out central. getting on plane was ridiculous with those.

The best props are 26" Bravo 1's. easy planing. Awesome cruise. top end gets knocked down a few MPH but it is well worth it unless you are just running flat out all the time. They have the best MPG and distance ability because you can easily run 50MPH all day long at cruise. The 25 M+'s don't respond well until the higher RPM's.

With the 25 M+, if I plug in 25 into the prop slip calculator, I'm at 5% slip. If I plug in 26 (supposed to add an inch because of the extra cup in the M+). I'm at 9% slip. That's on a fully fueled boat with 4 people.

I'm starting to realize that people's prop of choice on the 28ZX depends on how they boat and where they boat. I run out in the Gulf of Mexico and it gets rough frequently. The 3 blade prop just is not the prop of choice. They air out very quickly in the waves. It's a mind F@#$ if you have to slow down in rough weather because you don't know how long it will take you to get back on plane. The Bravo 1's though... don't air out in the rough stuff, stay connected very well at all times which allows you to really change the boat's running angle, planing is no problem at any time.

I think 25" Bravo 1's would be 'perfect' so I might have a set created at some point.

i give up about 3 mph when i run my 4blade compared to my 23 M+ but the boat handels, is more responsive, and get out of the hole with what ever load i have.

Tug, I think we may have spoken today.
Let me know if not.

Brett