I have an older bravo on my 24, I'm guessing its a 96. On my 21 I have a newer bravo with the low water pickups- not a sweptback, has some newer style graphics.

Is there any real difference in strength of these drives or are they about the same?


I can get serial #s when I get back home if needed.

The OM serial numbers were much improved and had the thicker gear floors, Don't remember what year the change was. Check the BAM website for more info.

Newer gears have thicker floors, but I think the older gears were made of better steel.

http://www.go-fast.com/mercruiser_bravo_sterndrives.htm

Thanks... I remember seeing that chart a while ago.. forgot where.

I have an OF and a OM drive.. looks like the OM is a little bit stronger... don't know if its a huge improvement over the OF, though.

I thought the steel gear strengh issue was on XRs?

The 90's cases were thin in spots, and the newer ones look thicker in different areas. The gear design changed, but the material I believe is the same. Setup has changed on the uppers, Merc uses a better process to check lash. Before you just matched the shim thickness stamped on the case and put it together.
A steel tower in a case is a big improvement along with a top cap with steel tower, locates the gear stack and if you have a tooth failure (not that common in the B1's, unless excessive power is applied) the steel tower wont go egg shape or crack below the surface like the aluminum one will.
The B1 S has a steel tower in the case, a steel tower can be installed in a non X case, the XR ribbed top cap has the steel tower also. My perferred setup.

Your right the XR upper gears seem to be having a problem these days. Older gears (early 2000's) would last 250-300hrs with moderate power applied (700-750hp NA). Heavier boats, could tolerate lower HP numbers, but they would wear out. These days the XR uppers will snap teeth off. Some say from shock loading. But I have seen it in cases where shock loading supposidely did not come into play. Hard to say, all hear say.

But you are correct, the new the Bravo the stronger it is, but how strong, could be a tiny bit or more.
I know people that used to blow the floors out of the thin gears. And I know people that still run them without a problem. 97 was a good year for B1 helical cut upper gears. Friend of mine has 650 hrs on his, freshened only once with bearings and lower gears were shot. Uppers still going!!

Hope that helps.
Dick