Bravo 1 vs XR / Speed vs Speed
 

I was running Bravo 1 1.36's in my 370 Baja. I upgraded power years ago and am running 600+ HP. I have recently upgraded to XR's with 1.35's gears. I have benn told that I would loose speed going to XR's of course Mercury Racing says never. Can anyone put the debate to rest for me. I seem to have people on both sides.
Thanks in advance.

I could not see where u would lose speed !????

Larger gears, more friction= slower

HAHA,,,,what .02 MPH ???? thats bs.

I bet you do not even notice that !

That's what I've been told... but then again you sound like you know it all- just not the answer!

:rolleyes:

I lost 2 mph switching to an XR.(gps) I was told it was because of the straight cut gears in the drive.

I am wondering if that loss is after the new drive was broken in?
My point is, take an nicely loosened up B1 that has a stack of hours on it.. then switch to a new tight XR and see a speed loss. After 50hrs or so on the new XR does the speed come back, or is it in the middle of summer heat and the power is down? Does the new drive have the same water pickup/nose cone?

I can see the theory of more drag on the gears, especially the XR's that grind metal off to them to break in. I just wonder if anyone has looked at it very carefully and when they made the switch, made sure the only thing that changed was the upper gears???

Just thinking out loud here. I know the general conscense is that there is a loss. I have not had the opportunity to test it out.
Dick

I have a 353 Fastech and went from Bravo 1's to XR's a year ago. I went from 81.9 MPH GPS to 78 MPH GPS. This has not changed in cool weather of hot.

I went from a stock Bravo 1 and replaced the upper with an Imco Extreme Advantage SC. I lost about 100-150rpm and 1-2mph on the top end. This was in my Pantera 28.

The stock upper blew apart at 210 hrs. The Imco was still going strong with 280hrs on it when I sold it.

?? Did you loose just top end or did your Midrange suffer the loss as well. Did you expext to loose MPH when you made the change. That is a big loss in speed to go to XR's. Why doesn't Merc own up to it. It pisses me off I can't get a straight answer form them.

Thanks for your response.

kevin

Well there is the answer, from jkelly and griff. Sounds like you guys have had the experience, and the result is a loss! Next question, how much loss from XR to Bmax?

If the mph loss is caused by the gears, wouldn't there be a lot more heat in an XR?

On my 25 daytona. No loss at all actually gained 1 mph. :ernaehrung004:

rbtnt,
The XR's do run hotter, not that I have had a guage on each, but that is what is reported. I also see the powder coating in the interior of the XR's falling off, and indication of heat, I believe.

QW,
That stands to reason the Bmax uses a helical cut gear. I just assumed, because of it's size that there may be a loss..
Dick