Bravo 2 Outdrive - Can I swap lower unit to Bravo 3?

[tdcooper99]

Hi, I've covered some of this in another topic... I'm considering swapping my current Bravo 2 drive for a Bravo 3 that a friend has for sale. However, it is proving somewhat logistically challenging as I am in Canada and he is in the US... literally 30 minutes away... but with the border closure it's a problem.... he can't bring it across personally meaning I'd have to ship it and incur taxes etc.

He mentioned that the Bravo 2 and Bravo 3 UPPER units are identical and that if I could find a decent reman. or used lower unit I could actually just swap the B2 lower unit for a B3 lower unit.

Not that I don't believe him, but I'm seeking a second opinion.... is this accurate? There seems to be more decent used or remanufactured lower units with warranty on eBay than complete units... so if this is a viable option, I'd consider this.

[Nauti_Mike]

Your friend is correct but you should verify if the gear ration in your upper is correct with a B3 and your engine. Most likely is.

[tdcooper99]

My gear ratio is 2.00:1.... his complete unit is also 2.00:1. If I do go with just a lower unit, what I am looking at is something like this:

https://www.ebay.com/itm/90-DAY-WARR...o/264988563478

There are other examples which state the lower unit can be used for GR 1.80, 2.00 or 2.20, and from what I understand this is relating to the tooth count of 16/27?

[builderdude]

Correct, 1.81, 2.00 & 2.20 all use the same lower gear combination 16/27.

[Nauti_Mike]

Yes the upper determines the final gear ratio so installing a B 3 lower will still be a 2:1 ratio. What I don’t know is what is the recommend ratio of a 7.4 with a B3. Most likely it’s 2:1 and you’ll be good but I would verify with Mercruiser or their manual on engine/drive packages.

[tdcooper99]

Yes the upper determines the final gear ratio so installing a B 3 lower will still be a 2:1 ratio. What I don’t know is what is the recommend ratio of a 7.4 with a B3. Most likely it’s 2:1 and you’ll be good but I would verify with Mercruiser or their manual on engine/drive packages.

I've been trying to Google this, but can't seems to find a definitive reference. You wouldn't happen to have a link to a reference chart or something would you?

[Nauti_Mike]

i do not.

[tdcooper99]

Tbh, I think I'm ok at the 2:1 ratio... been reading loads of other forum posts with guys with various configurations... but it seems most of the 454s/7.4s on similar sized boats to mine have the 2.0:1, but the prop pitches vary depending on the boat. I have resigned myself that I may very well need to drop down a pitch to 19p, from the current 20p cupped. My friend says he'll take the props back and give me some money back... so I wouldn't be massively out of pocket. He even insists that an in-water prop change is possible to avoid another haul-out just for a prop change... he's done it. I'll remove and regrease the current props before re-launching to make that easier, but not something I'm looking forward to trying.

[Nauti_Mike]

Changing the props in the water isn’t too bad of a job. The B3 rear prop nut is the same size as your B2 but the forward prop nut is much larger. The B3 doesn’t use the tab lock washer.

[tdcooper99]

Changing the props in the water isn’t too bad of a job. The B3 rear prop nut is the same size as your B2 but the forward prop nut is much larger. The B3 doesn’t use the tab lock washer.

Good to know for an emergency... I've ordered a B3 prop wrench from The Prop Shop in Mukilteo... but I just came from the yard where my boat is on the hard and spoke to the owner, he said in the off season for something like a quick prop swap, he'd haul me back out for $100... so I think that might be money well spent for the convenience. Heaven knows we've all spent more for less benefit on our boat at some point! 😉

[Nauti_Mike]

For $100 that’s money well spent vs the effort of doing it in the water.