Found a pair of rebuilt zero hrs XR lowers pretty cheap and was thinking of up grading my lowers.1 of my lowers has a slightly twisted prop shaft and to up grade them with XR gears and 1.25 prop shaft is about the same price as these XR's.Just want to make sure they will bolt up to bravo 1 uppers.Then I will just have to send the uppers to Mr Gadgets.

swap will work but. XR has one set of gears in upper and ratio change is done in lower. As a regular Bravo One the change is done in upper, three different gears set available and only one set for lower. So you need to find out what gears set is in the XR lowers you are looking at, then check Merc gear chart to make sure you will land up with the final ratio you want. Also check to see if your upper has same oil hole as the lowers your looking at, there is a chart with pictures that shows comparability I think the chart has been posted on another post here on OSO

Thanks Clustergear, that answered a lot of my questions and concerns! My next issue is I thought the drive ratio on this 300 xp I just bought was 1.50 but couldn't read the tag very well.But took a real good look today and it's 1.36.I assume this will work ok for my app but will put more stress on the drives then if they were 1.50. Anybody that could give me some advice on this would be greatly appreciated! Thanks!!!!!

The bravo 1 lower gear teeth count is 15/19, that holds true to all, as Clustergear mentioned the ratio in a std bravo is changed in the upper.

A 1.5 geared XR also uses a 15/19 gear set in the lower ( same as std. bravo ) a 1.25 or 1.35 geared XR has a 17/18 or 15/17 tooth count

So, if the XR lowers you are looking at are 1.5 ( 15/19), you'll net the same ratio as you currently have

Thanks JaayTeee!! Just so i under stand you correctly,a lower from a 1.5 XR bolted to my 1.36 Bravo upper will net me the same 1.36 ratio ?

That is correct