How to count teeth bravo outdrive ratio

[Rotorpilot1969]

I have a B-2 with a B3 dual,prop foot, I bought this drive used and it works great but I've had other boat issues with low rpms and starting to think the ratio on my outdrive is wrong for my boat. I need and thought I purchased a 2.20 ratio as stated on the side case but seeing this drive has been turned in to a B-3 I'm wondering if the gears have been changed. I removed the top upper cover and can't see so well but think I counted 32 teeth but was wondering what is considered the drive gear? The gear I counted 32 teeth on I believe is the driven gear. This could still leave me with a few other choices depending on what the drive gear is. Where is the drive gear and is it viewable without removing the drive.

 

[Bt Doctur]

http://www.boatfix.com/merc/Servmanl/11/11a3r5x.pdf page 3A-9

 

[Fun Times]

I have a B-2 with a B3 dual,prop foot, I bought this drive used and it works great but I've had other boat issues with low rpms and starting to think the ratio on my outdrive is wrong for my boat. I need and thought I purchased a 2.20 ratio as stated on the side case but seeing this drive has been turned in to a B-3 I'm wondering if the gears have been changed.

Keep in mind that there are different size gear ratios within the bravo three lower units that will change the overall gear ratio when mixed with different upper drive shaft housing gear ratios.

While in Mercruiser service manual # 11, you will also want to see page 3D-3 for the gear teeth count ratio chart of the B-3 lower gear housing.

Just found this discussion you may be interested in seeing.
http://forums.iboats.com/forum/engi...ir-i-o-and-inboards/657761-bravo-1-to-bravo-3

 

[Rotorpilot1969]

Thanks because I couldn't find this answer. I noticed the gear chart gave different ratios for the same upper gearing on a few types. I'm guessing on these the final ratio is determined in the foot? Can I count teeth in the uppers and the lowers to find my gearing without removing anything?

 

[HT32BSX115]

Howdy,

It might be easier if you just turn the input shaft 10 turns and count prop turns, then divide. (input turns : prop turns)

If you don't have the drive off, then pull spark plugs, turn the crankshaft 10 turns and have a help count prop turns. (actually you can turn the input shaft/crankshaft ANY number of turns if you can measure fractional prop turns......one blade on a 3 blade prop is 0.333 and 0.25 turns on a 4 blade etc)

You can get pretty accurate using the above method.



Regards,


Rick

 

[Rotorpilot1969]

Ok thanks. I was trying to avoid pulling plugs. Afraid ill snap crank bolt. Been there done that. Yuk!

 

[HT32BSX115]

Ok thanks. I was trying to avoid pulling plugs. Afraid ill snap crank bolt. Been there done that. Yuk!

Is that "thumping" I hear in your voice?

Yeah......Don't try to turn it against compression......

It can be a bit of a pain pulling plugs but if you haven't looked at them in a while, it might not be a bad idea anyway!

But you WILL know the ratio after you're done.