Changing drive

[alldodge]

My guess is that the drive has been replaced. When a dealer buys just the upper it doesn't get stamped. Easiest way now is pull the drive and count the revs

 

[ericcarr2000]

Just had to start stripping the part under the Mercury sticker and found the numbers od351140 which coincide with the outdrive numbers stamped on the cover of the motor.
Which ratio is this?

 

[alldodge]

Shows up as a 1.50

Edit: and here is the link so you can look it up
https://www.mercurymarine.com/en/us/parts-and-accessories/parts-catalog

 

[ericcarr2000]

Ok so if I go with a 2.00 or a 2.20 that should get me on plane quicker then?

 

[HT32BSX115]

Ok so if I go with a 2.00 or a 2.20 that should get me on plane quicker then?

The same "rule" of thumb usually applies here..... with "proper" gearing and prop(s), the engine should turn at or near the top of the manufacturer recommended RPM range when at WOT with the boat loaded at the weight you'll typically operate at.

You should even be able to get with Searay and get info on the Bravo III ratio/propsets they put on current and older 250 Sundancers and similarly sized hulls.

You should probably focus on the older carbureted 7.4L engines....... Those engines typically seem to be rated at 4600 MAX RPM where the MPI's appeared to be rated at 5000/5200 etc..... The 2.20 and 2.43 drives seem to be paired with the higher RPM engines (2.43 drives are frequently used at high altitude)

 

[alldodge]

If you had a 5.7 I would think a 2.0 but with a 5.0 I would more think a 2.2
Would be nice if you were closer, I would let you try a 2.0 drive, but would think the 1.65 wouldn't help. What pitch prop you turning now?

 

[HT32BSX115]

Ok so if I go with a 2.00 or a 2.20 that should get me on plane quicker then?

It won't be the lower ratio that gets your boat on plane quicker, it's the 3 additional contra-rotating blades that'll do it.

The lower ratio will allow you to more efficiently turn those 22 or 24p blades

 

[HT32BSX115]

If you had a 5.7 I would think a 2.0 but with a 5.0 I would more think a 2.2
Would be nice if you were closer, I would let you try a 2.0 drive, but would think the 1.65 wouldn't help. What pitch prop you turning now?

OK.....I am slightly confused.......Didn't he say he has a 90 model year 7.4L carbureted V-8?

 

[alldodge]

OK.....I am slightly confused.......Didn't he say he has a 90 model year 7.4L carbureted V-8?

Doah :facepalm: my bad, got this one mixed with another. In that case you want a 2.0 and start with 24 pitch. This is what my 11K boat came with and had a hard time getting out of the water. Your lighter so it should not be an issue if your engine is strong

 

[ericcarr2000]

I currently use a bravo 1 with a 3 blade 10 pitch ss prop.

 

[alldodge]

I currently use a bravo 1 with a 3 blade 10 pitch ss prop.

Agree with a 1.5 drive spins the prop faster then the 2.0 ratio. You cannot use the same drive ratio because they don't make a prop lower then 18 pitch.

Case in point, my 530hp engine with a 1.65 ratio B3 and 24 pitch props would not get me up on plane, the 22 pitch did get me up but barely.

 

[thumpar]

I currently use a bravo 1 with a 3 blade 10 pitch ss prop.

That can't be right. I don't even think there is a prop less then 15 for a Bravo.

 

[alldodge]

10 was a bit much for me also but found iboats has 11 pitch
http://boatpropellers.iboats.com/Me...1.00&chart=77&engine_id=774&cart_id=397211813

 

[ericcarr2000]

Darn it, lol stinking keyboard. I meant to say I currently use a 19 pitch....

 

[ericcarr2000]

So I think I'll go with a 2.0 ratio and s 22 or maybe even a 20 pitch prop set then...

Doah :facepalm: my bad, got this one mixed with another. In that case you want a 2.0 and start with 24 pitch. This is what my 11K boat came with and had a hard time getting out of the water. Your lighter so it should not be an issue if your engine is strong

 

[HT32BSX115]

So I think I'll go with a 2.0 ratio and s 22 or maybe even a 20 pitch prop set then...

If you think you'll need a 22 or 20p propset, you should consider getting a 2.20:1 drive.

That way you have a tad more leeway with props. Especially if you're considering rebuilding your engine and maybe upping the max RPM to 5000 RPM.

A 2.20:1 drive with a 24p propset would yield approx 40 MPH at 4600 RPM with 15% slip. that's not unreasonable for a boat your size.......

But to do that, you won't be able to just bolt a lower on your current "upper" You'll need to find a 2.20 Bravo III drive.

But assuming there's nothing wrong with your current drive, it's valuable on the used market.

 

[ericcarr2000]

Ok, I have an opportunity to pick up an 08 bravo 3 drive with only 40 hours on it with a gear ratio of 2.20. I also have an opportunity to pick up an 04 bravo 3 drive with transom assembly and trim Rams. Both of them come with a set of 24 pitch props. Which one would be the better deal?

 

[alldodge]

If they are both 2.20 drives then get the one with the transom assembly. That is if they are both in good shape internally. A bravo drive taken care of will out last the boat. Now if the 04 is a 2.00 ratio IMO that's the one you want.

You can sell stuff you don't want off the transom

 

[Blind Date]

"is it true that a bravo 3 drive would loose some top end power vs the bravo 1?"

I doubt it. My '97 250 Sundancer, which I believe has the same hull below the rub rail as your '90 250 runs 42-43 MPH all day long with a 5.7/EFI. You said your BB boat currently runs 35 MPH. That seems really slow to me. How can my boat be that much faster? Something doesn't add up.

Anyways I think getting rid of the B1 and upgrading to a B3 is about the best money you could spend on that boat. Once you run it with the B3 you'll NEVER go back to a single engined cruiser with a single prop drive.

 

[thumpar]

I think the 2.00:1 drive will give you a better selection of props. Those seem to be one of the most popular propsets so you can get some deals probably.