Will a '99 20' Cobra do 77mph w/225 merc?
Will a '99 20' Cobra do 77mph w/225 merc?
SkeeterMark...I would say no. Maybe 72-74 mph would be about the limit under ideal conditions. Now if the boat is being pushed by a big block Yamaha and it had some prop work done, non tourney load, 1/4 tank of gas and a slight ripple on the water during the cooler time of the year it might reach mid 70's but 77MPH is pushing it a little bit IMO. Most of the folks running 201's with 225 HP run anywhere between 68-72.
I thought I would be on Easy Street by now but somehow I missed the off ramp!
I was just curious. Have a guy in the club spouting off at the mouth and how his '99 Cobra could hang with an '02 Blazer. Thanks.
Backlash hit the nail on the head as far speed of these boats. We did get a '99 w/225 Merc to run 76 GPS though with a 12" jackplate, one person, no load and a tweaked prop. This boat was also a composite boat. Perhaps the guy is talking about 77 on his speedometer!!! We had lots of them that would hit 80 on the speedo!
Ok Ben, we're all ears, what is your set back and how high are you running the motor?
What kind of RPMs are you turning for that Pro Max? Aren't they about a 7000 rpm motor?
I thought about trading mine for the same year model boat with a Pro Max, but read where those motors didn't do well with the heavier hulls, obviously you have figured it out. Has there been any "tweaking" to the motor?
That's pretty good running Ben. I ran some numbers thru the Prop Slip Calculator and it seems that you are getting a fair amount of prop slip.
1.62 Gear=Theoretical Speed=96, Actual 76 or 21% Slip
1.75 Gear= " " =89, Actual 76 or 15% Slip
It would seem to me that a bigger Prop would cut the RPM's down and give you more speed an may be more efficient. If you could say turn a 27 Trophy at 6200 you may gain some speed.
Ben.
I was just told about this web site this afternoon, I have found it very interesting.
Have you experienced any problem with the transom with the increased setback? When I purchased my 99 201D with a 225efi 3 lt. Viper stated they would only stand behind the boat with a 8" or less jack plate. At this point this doesn't mean much. I haven't tried anything but a 6" and 8". Tourney rigged, full tank of gas, 2 big boys the rig runs 63-65 at 4300 ft elevation, 70-71 at 800 ft elevation. The power head was replaced by merc with a 2000 production power head, I have been told they detunned from the 99 version, I lost 3-5 mph, it ran 68 at 4300 ft. I have raised the cowl scoop and drilled air holes in the cowl as well as installed a 4 port air box to compensate for the factory detunning. I am running a powertech TRO 23P highly modified lab finished by Marine Prop in Utah. I have tried many props and settled on the powertech. I run the boat primarily at 4300 ft. elevation. I have the need for speed but don't feel I can justify buying a Allison or Bullet. I have left the 225 stock trying to keep the reliability. I am looking for information on how to make my 201D a faster rig with out spending a ton of $$$.
Ben.
Thanks for the information. I keep my boat garaged at the lake, I will be there in 2 week ends, I will look at the bottom and check out what you are talking about with the chines. Can they be sanded only or is there glass repair/jelcoat work that will need to be performed. As far as the transom, I wasn't concerned about the set bach plate weight, I was concerned about changing the pivot point and adding extra stress on the transom during hole shot and acceleration. I would hate to break the transom out of the boat. Is this something to be concerned with? This boat was manufactured in 1998 and used by a factory sales rep until I purchased it. As far as the prop, I currently run 5400/5500 rpm at 4300 ft. elevation. The speeds I mentioned are GPS and when I was testing created a spread sheet showing engine height, prop, speed, rpm, water pressure and hole shot. The boat seemed to run best with the powertech as high as I could go at 1/4" intervals, when the water pressure dropped, I backed it down a 1/4". I would like nothing more than to have to go to a larger prop. Again thank you for the information.
Reply With Quote
