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View Full Version : XMP vs Ambush4 I want top end increase


bdemare
08-25-2005, 12:59 PM
Ok I have read alot of posts about props but not to many on which one people recommend. I want a new prop. can anyone tell me that one is better than the other or they are about the same as long as I get a CNC prop.

The boat is a Tristar 1988 351 with a powerslot 1:1.5 and Want TOP END increase because I have the poweslot. I am running the orginal prop now. I called Skidim they recommend XMP 4 blade but was unable to tell me if i would get top end increase. I tried calling OJ and talk to eric but he was busy and some lady to me told me that i needed 13.7 x 17.5 to replace my prop. Have not called Michigan yet. any thought

thank,
Bryan

east tx skier
08-25-2005, 02:05 PM
Call Bill at Acme while you're at it.

J. Patterson
08-25-2005, 02:30 PM
I'm curious. I have a 1990 Tristar with Ford 351 with 1/1 velvetdrive and 13/13 OJ 3 blade. I top out at 44---45 mph and just a tick over 4000 rpm.
Mind sharing what your numbers are with the powerslot? 44 mph is plenty fast for me, but I bet your boat is smoother- quieter with the lower rpm prop shaft. You are probably closer to your power band at skiing speeds too.

J. Patterson

east tx skier
08-25-2005, 02:45 PM
J Patterson, I'm amazed you're getting 45 mph at 4,000 rpm. I'm getting that, but at 4,600 rpms.

alecams
08-25-2005, 03:11 PM
I have always though the more pitch on the prop the higher top end speed and lower RPM. A shallower pitch prop will lower your top end (quicker hole shot) but then you are in danger of high RPM's.

bdemare
08-25-2005, 04:33 PM
I have not ran the numbers yet snice i just got the boat last week. The last time I was out I forgot my gps. I plan on going out next week will let you know what i find out.

J. Patterson
08-26-2005, 10:13 AM
east tx---

13X13 prop = 13 " X 4000 rpm = 52000" inches per minute / 12 = 4333 ft per min less 10 % slippage =3900 ft per min X 60 = 234000 ft per hour / 5280 = 44.3 miles per hour. You must be powerslot or have a prop with less than standard 13 " pitch.
?????????
My son's Nautique with PCM 1.23 to 1 trans runs rpms similar to yours.

Have a Great weekend. Schools started. People have minds on football starting = less crowded lake. Glass water on the slalom course in the morning. Can't wait!

J. Patterson
Trussville, AL

east tx skier
08-26-2005, 11:00 AM
JPatterson, that post made my head hurt. 8p

The reduced pitch is pretty standard with the CNC'd props. My WOT numbers were the same as with my OJ 13x13 legend.

I'm running Velvet Drive 1:1.

pilot02
08-26-2005, 11:02 AM
I'm curious. I have a 1990 Tristar with Ford 351 with 1/1 velvetdrive and 13/13 OJ 3 blade. I top out at 44---45 mph and just a tick over 4000 rpm.
Mind sharing what your numbers are with the powerslot? 44 mph is plenty fast for me, but I bet your boat is smoother- quieter with the lower rpm prop shaft. You are probably closer to your power band at skiing speeds too.

J. Patterson

Are these speeds timed through a course? That prop must have a fairly substantial cup to be running that low on the RPM's and that speed. My 89 tristar 240 hp 351 runs 41 mph at 4405 RPM with the 1:1 and 13x13.
Also, RPM limits for that engine should be 4200-4400 RPM if it's the 240-250 hp and 4400-4600 if it's the 285hp.

bdemare
08-27-2005, 01:01 PM
Are these speeds timed through a course? That prop must have a fairly substantial cup to be running that low on the RPM's and that speed. My 89 tristar 240 hp 351 runs 41 mph at 4405 RPM with the 1:1 and 13x13.
Also, RPM limits for that engine should be 4200-4400 RPM if it's the 240-250 hp and 4400-4600 if it's the 285hp.


does anyone have any experience with a powerslot and a new cnc prop?

whitedog
08-27-2005, 10:54 PM
Just for your reference: 1988 190 tristar 351 HO 280 hp 1:1 velvet drive. 4400 RPM 45 mph (gps) with a 1/2 tank gas 3 people on board with a 13x13 4 blade ambush. This prop does have quite a bit of cup on the blades. Pulls two teenage footers at 42 -43 mph all day long.

J. Patterson
08-29-2005, 12:10 PM
Your speed vs rpm posts made me doubt my memory so I GPS checked my speedos and checked rpm Saturday on the way to the course. Heres what I got. (351 with 1/1 velvet drive and an OJ 13 X 13 three blade. ) Top end 43 mph (bimini up :) ) 4300 rpm. So my rpm was a bit higher than I remembered, and my top speed was a bit slower. Thats kind of the way I remember my skiing too ;)


J. Patterson
Trussville, AL
90 Tri Star 190