575sci Lower End...What RPM?
 

What RPM can the 575sci lower end safely take in top end bursts? Im not talking holding it WFO for miles on end...just makeing short top end runs like we all do.

The rev limiter will kick in at 5300-5400 unless you've modifie dteh computer. No reason to spin it faster without major mods.

Aware of the rev limiter...most likely changing heads/cam and would like to know what the bottom can handle. I have also read you do not want to bounce MEFI3 off the limiter so it is going to get bumped up for that reason also.

JRider, what are you running for a prop and drive? have you ran a 5 blade on your boat? what kind of speeds are you getting with the 575sc? I have the same boat, just wondering how others are running.
thanks
larry

Rev limiter cuts fuel, and therefore will melt a piston if you constantly abuse it. Stock limiter is a t 5400 but you can safely turn the short block 5800rpm. The problem is the valve train and the flat tappet cam, which does nothing at the high rpm. Because you have a cat, you would still see a gain in speed with more rpm though, therefore, it's worth looking into.

Dustin

5800-6000 RPM . More in relation to the hyd. roller valve train. The bottom ends have components that would handle more than 6000 RPM.

1.5 XR drive. The prop was originally a 30 bravo repitched, lab finished and stamped 32 by merc. I personally feel it is more like a 31 due to slip numbers that seem unrealistic for the hull. I am hitting 93 fairly easily. I dont believe a five blade would do much for me except overload an already stressed XR. However I would love to try a hydromotive quad 4.

Dustin and MRhorsepower, thanks for your replies. You have confirmed my suspicions.

over all, how do you like your cat, do you get any porposing around 70 or 80, how is it out of the hole. hope you don't mind the questions, but there are not to many profile cat owner's on here.
thanks
larry

No problem. By the way, nice avatar, too bad it wasn't a bit bigger! :D

Dustin...when get home I will post the full size just for you.

Hoozeyurdaddy...no problems at all with porpoising. x dim. is not real high and boat runs the fastest with neutral trim. In my opinion it is a very efficient hull. I remember hotboat did a test on it in i think 2001...it was the fastest single 28 they had tested with a 575sci to date.

Two other setup things... I am going to fab up a 3/16" stainless "whale tail" to get on plane faster to take some stress off the drive. I am also going to work on getting more air in and out of the engine bay.

What is your setup?

Have you thought about adding an intercooler?

I'm running a 622ci naturally asperated, dynoed at 830hp@5800rpm, Imco SC standard with a extesion box up 3in, I do all my boating on lake powell, elevation is 3600 ft. I'm running a 26P B1 and 1.34:1 gears at 5600rpm, gps between 94-96,
I would like another 2 or 300 rpm but not sure where to get it.
I've looked at 5 blade props or have the 26 labbed, this boat is slow to plane, but as soon as the bow drops rpms come up and your off, prop is 15 1/4X26, looking at a 14 1/2X28, what do you think the out come would be. where are you going to put the whale tail? on the hull or drive?
thanks for the info.
Larry

I would love to add a intercooler but have ran into a few problems. I dont have clearance for even the whipple low profile cooler(which is a very nice piece). I researched cutting the hole, or adding a scoop, and also having a whole new hatch made...just too much money (beside the cheesy cutting a hole thing). My cocpit cover and mooring cover would have to be redone also. Even if I did add the cooler I would be spinning the little 256 even faster.

So...I think my money is better spent on getting more air in and out of the engine bay, dropping the thermistat to 120*, 3.5" pulley, aluminum heads (think I will end up with canfields), camshaft, and ECM remap and upping the limiter. I think this will reach max out the injection, blower and pocket book.

The 575 is what it is, small blower, small throttle boddies with great lower end...sounds like Im talking about my girlfriend! Oh, **** cam also.

I looked into tunnel tabs but fabbing a whale tail for the drive is a lot cheaper and that lets me spend more money on the motor. Here is some example of tails.

Gotta love tan lines!

I think you guys would both really benefit from 5-blade Hydromotives. If your having trouble getting on plane, then you have a pretty high X, and the 5 blades work really well for that. But if your running a 26, I would say the boat would do better with more pitch, different gear. I've found the single engine cats need 1.5 gears and large prop pitch to carry nose at high speed. Just my .02

575 lower end
 

J rider, call randy schultz , I traded my tall scooped hatch for his low profile scooped hatch, I had the 575 with the superchiller kit on mine. he has other hatches also, call me if you want his number. dean 612 978 9897.

Hi Jeb,
With the stock cam, I have turned 5600 with no issues. With the hydraulic roller, 6000, no problem (except the XR drive).
The chicks are looking good. Maybe we can work a trade out :cool-smiley-011:............
Regards,
Steve

Steve...you better upgrade your spark arrester! I didnt know merc made a 540ci 871 version...lol

Once you get into changing the engine from stock, and wanting to remap the efi it really requires a dyno tuned expert. I have gone through all this this past winter. Have you looked into the Arizona Speed and Marine kit? They have taken all the computer recal quess work out of it. They sell all the parts and will recalibrate for you. With their kit fit?

After what I went through this winter with my Whipple and aluminum heads, I'd would have kept the stock heads and had Whipple do the computer. Strickly for less head aches.

Here is their kit, they claim 80 hp. Thats not bad for bolt on items. http://www.azspeed-marine.com/me575sciboki.html

Jeb,
It's a little 509", and you know, the insurance thing :D.........
Regards,
Steve