Bravo III gear ratio and cone clutch

[MightyEsquilax]

I had to go the route of sanding down the port side of the Bravo III upper gear housing to pick out the S/N of the drive. I was under the impression the gear ratio was also stamped with it. But, as you can see from the picture, I only got the first seven digits with the last un-readable and the gear ratio is no where to be found. Does this mean I need to tear open the upper gear housing to figure out which ratio I have? I've heard of counting teeth but which gear do I count the teeth on?

The boat is a 1996 Sea Ray 250 with a Merc 7.4 and Bravo 3 drive. I'm pretty sure the Cone Clutch is shot because forward gear is grabbing late. It's not the drive cable, I've shifted it by hand on the water. What's got me really nervous is instead of buying a new Cone Clutch for $360 I might need to by a whole new gear set because a new Cone Clutch may not match the original 1996 gear set, any truth to that? Merc stopped making the gears for my drive in 1999 and they said you needed to by a new gear set with new shims. I *think* I read on the service bulletin that you can tell which gear set you have based on numbers stamped on the shift fork and other parts... There's a chance someone replaced the gear set before I got the boat (I hope)... Has anyone just replaced the Cone Clutch without the gear set? Or is it an issue with the clutch just not fitting because of the size difference?

Thanks!

 

[HT32BSX115]

Howdy,

Just pull your spark plugs and have someone count blades with the drive in gear while you (manually) turn the crankshaft.

2 revs of the engine will be 1 turn of the prop if it's a 2.00:1 drive

My Bravo III is a 1.81:1 ratio..... so slightly less than 2 engine turns is 1 prop rev

At 1.81:1, it would be exactly 1 turn plus 291.6 degrees of turn(pretty hard to measure unless you use a protractor) ...........

So, just turn the engine 18.1 times (18 turns+36 degrees) and have your helper count (10) prop turns etc

Cheers, Rick

 

[scoflaw]

Of course, replace clutch and deglaze the cup on the gear.

 

[Fun Times]

Close enough on the serial number that no matter the last number any number you use will bring up the same bravo 3 drive info all with the same gear ratio for any 0-9#'s inputted from new....I'd say your last number is an 8 though.

0F806618 = 1996 MERCRUISER TWIN COUNTER ROTATING PROPS BRAVO 3 2.00:1G.R Model Number 5D30200JT.

Search iboats/online Mercruiser Cone Clutch "Lapping Compound" as changing/roughing up the surface structure of the internal parts some may help you avoid buying new gears, etc..

 

[alldodge]

To make up the ratio the B3 uses the upper and lower sets to get the overall ratio. For the cone clutch count one of the clutch gears and the drive gear.

Given that FT has the ratio so should be 16/27 upper

​
Hear is the gear change bulletin
View attachment Bravo Gear change Bullentin.pdf

 

[MightyEsquilax]

Wow, all great information. Thanks very much to all. A couple of follow up questions.

Fun Times- Where did you find the the Model number of the bravo? The mercruiser website I went to didn't help. I'd like to use whatever site you have for future reference.

I will look up the cone clutch lapping etc... I had heard of that technique but didn't know if it was worth it.

Last question, do I need to split the drive to tear down the upper gear housing? My thought was NO but I didn't know if anyone had experience.

Thanks again!

 

[alldodge]

The manual (number 11) shows to split the drive, and will also need to do shimming and preload (possibility). I pulled the top and back off the upper, and rebuilt the lower B3 before. I would suggest doing as the manual shows

 

[Fun Times]

Wow, all great information. Thanks very much to all. A couple of follow up questions.

Fun Times- Where did you find the the Model number of the bravo? The mercruiser website I went to didn't help. I'd like to use whatever site you have for future reference.

I will look up the cone clutch lapping etc... I had heard of that technique but didn't know if it was worth it.

Last question, do I need to split the drive to tear down the upper gear housing? My thought was NO but I didn't know if anyone had experience.

Thanks again!

Just input any of the 3 serial numbers you may have at the top of the following link, https://public-mercurymarine.sysonli...=englangDB=eng

Lapping could be either a permanent thing or temporary thing...Either way it would be worth trying for your situation especially if you do it yourself due to if it don't work then you'll really know if you need to buy all new parts, etc.. Some service dealers may or may not want to try the lapping compound though.

There are videos online of how to take the bravo drive apart but first you could try pulling the top and back cap and pulling / inspecting the Yoke area item # 11 to help see what's going on with yours, https://www.mercruiserparts.com/bam/...30967/1943/210
https://www.mercruiserparts.com/bam/...30967/1943/190
https://www.mercruiserparts.com/brav...-thru-0m100000

Some special tools listed in the Mercruiser service manual number 11 may be needed though too.

 

[QBhoy]

All great stuff above, but have you checked the gear oil ? Water in the oil or the wrong oil can make the cone clutch slip.

 

[Formula280]

Pulling up an old thread here. I have my B3 upper taken apart because I was having shift delays. Does anyone have experience cleaning up the gear cups? There is a slight rust spot on mine