Just curious of who is running a zx180, with a vmax 150 with carburetors, what kind of speeds are you getting and with what prop?
I have a 2000 zx180 with vmax 150
I get around 55mph with a
25-M prop.

What rpm are you running WOT? I am not very familiar with that rig but it sounds like too much pitch. Looking up the motor on the net it seems max rpm is 5500, if you are way lower in rpm at WOT you would need to run a lower pitch prop to get the rpm up into the 5300 - 5500 range.
My carbed Merc 150 on a 19' Nitro won't pull a 25M and runs about like that with an awful holeshot. With a 22p Laser II or a 23p Tempest it's 63-64 mph GPS with a good holeshot.....but I am not sure of your lower unit gear ratio, and my max rpm is 6000.

WOT?
Without being trimmed up?

You're not far off from Yamaha/Skeeter's published configuration. They show 58 mph with a 25p prop.

http://yamahaoutboards.com/sites/default...0tlr-070908.pdf

I run the same hull same 150 HP mine is a Merc. I get the same numbers in summer running a 23 P Trophy stock. Havent completely dialed in since I added 8" Rapid Jack and blueprinted 23 P Trophy. It is faster just how much I will know very soon.

Strange we get the same numbers with 2 inches of pitch difference though. I cannot run a 25 on mine it only turns 5000 rpm with no hole shot. The 23 stock runs 5600 to 5800 rpm in winter will run up to 6200. Not sure what the 23 blueprinted Trophy will run.

WOT= Wide Open Throttle

Yamaha 150 gear ratio is 2:1. A quick google search suggests militarybrat's Merc 150 has a 1.87:1 ratio. If the Merc 150 is geared higher, it wouldn't be able to turn as a high a pitch prop as a 150 Yamaha.

That is correct on the 1.87:1 ratio of my Merc. I did notice the year my ZX180 is 1998 (1996 design) 18'3 long 89" wide. The newer ZX 180 is a 17"something in length and wider than mine. Still strange how they run the same MPH. On paper the OPs' boat should eat mines lunch that carbbed 150 V Max is a beast as far as 150's go add the shorter ZX hull should be no contest. Now if the OPs' boat is a ZX 185 it's even no doubt.

Awesome forum for this greenhorn. Getting expert advice, from guys thats been around the block a time or two!!
The information very much appreciated!

I ran a '96 180ZX for 8 years. Mine had a 175 HP Intruder on it though. When it was new, it would run 70 mph on GPS at 5800 rpm in winter and 68 mph at 5600 rpm in the summer. As the engine aged it slowed down about 3 mph. I ran 13.5" x 25 pitch Renegade 4 blade. I like the way a 4 blade prop performs over a 3 blade.

At 70 mph that boat would chine walk pretty bad too.

Do you know what your rpm is wide open? Where are you located? I have a stainless prop marked M24, not sure of brand but it is 15 spline for big Merc or Yamaha that you could try if you are around DFW...its for sale if it works for you.

Crowley

I have this one for sale but you can try it first, need to be able to check your wide open rpm to get it propped correctly....

http://texasfishingforum.com/forums/ubbthreads.php/topics/11511881/Yamaha_prop?_24m#Post11511881

A 23 tempest will carry that boat real nice. A balanced and blueprinted 23p tempest will carry it even better.