IMO, the Bravo is a very simple piece of engineering. I'm sure the pro's like Mr Gadgets have some secrets your not going to find in a book. Buy a #28 merc Bravo service manual and the #28 supplement and you will be on your way to being self sufficent in Bravo rebuilding. The manuals also give you all the part #'s on the merc tools you will need. I have around $500 or so in merc tools.

You can design the load sensing rev limiter,patent it and sell it to the industry. All I have is a MSD limiter.

LE

Are you running the MSD 'marine engine protector' thingy? If so would you mind me asking how you've got it set and how you're finding it? I can't see how it does anything more than an average rev limiter?
I want something that would miss a few sparks at random when out of the water to stop the revs jumping, without causing backfire issues etc.

James

your going to need some special tools also.

anybody know if the xr stuff will fit in the bravo?

Cool, any info really greatly appreciated!

Many thanks,

James

The lower XR uses a different prop shaft, carrier and driven/prop gear(std bravo gears can be machined to fit the XR shaft).

The upper uses a different case with a steel tower and the input part of the case is machined different, and has a different input yoke and retainer. XR and XZ gears have thicker floors that utilize a thinner clutch, and different bearings. U-joints are also bigger. Clutch shafts are the same except the newer shafts marked with a "A" I believe are suppose to be stronger.

Converting the lowers to XR is a affordable upgrade. Converting a std upper to XR is a little cost prohibiting. You can get a input UJ shaft to utiilize your std u-joints and new XR pinion gear(Max Machine). But after buying a gear set($1600), clutch($300), machining the case for a steel tower, and the rest of misc bearings and parts, your over what it would cost to buy a new upper(I've seen around $3300 for a new one), not to mention the used market.

Upper and lower Bravo units will interchange. An XR u-joint assembly does require a new/updated gimbal bearing(red dot) be installed in all early(before 2001 or so) transom assemblies. $120 bearing.


LE

The XR's do use some special tools also.

MSD blue marine boxes with plug in RPM limiter chips. I've been on them alot, they dont cause backfires or running issues, just hold the rpm to the set chip.

I'm currently running a 5800rpm chip. I need to reprop the boat(next year) because I'm on the chip at WOT. I try not to hit them when the boat comes out of the water, but I'm sure I might have once or twice.

LE

so prob the best thing is buy a set of xr's or some that need rebuilding, rebuilding that way ya know whats in them.Thanks for the info.


On the MSD it will zing past the rev limiter,that if theres a failure,jump out of water not backing out,or barking between waves,but that would be close to the rev limit.Again thats went it zings.the ones I have have been as high as 1000k above the limiter.

Thanks for the replies again guys, doesn't seem that the MSD box is gonna do what i want it to do. I'm running a foot throttle so should be pretty accurate with backing off, but it'd be nice to have a gadget there to save my ass if i miss one!

Is the XR upper particularly stronger than the standard bravo then? I've got two entire bravo drives here so could sell those on to buy an xr drive. One that needs rebuilding would indeed be ideal!

Cheers, James

I have had good luck with my MSD's, got 2 marine boxes on the boat and 1 red 6AL on a manual Mustang, and always seem to hit on the chips in each.

XR and XZ's will have the thicker floored gears, XR's get the steel lower tower, but I'm not sure if the XZ does. XR's have straight cut gears, while XZ has helical. dont know how much stronger the u-joints really are, but the XR does get bigger ones.

Std and XZ's uppers come in different gear ratio's, while the XR gears only come with a 19/16 tooth count. You can get an overall ratio of 1.5, 1.36, or 1.26 depending on lower gear ratio with the XR.

LE