wrong prop for drive?

[muskyfins]

At the end of last year I bought a 1995 Rinker 265 Viesta Vee with a 5.7L (260 HP) I just realized she has a non-original Bravo One from a boat with a 7.4L as evidenced by the sticker on it. I also believe the prop is from a Bravo 2 based on part numbers I've been able to find on it-1946R21. I believe this is a QA1946R21 which is a huge prop (17.75 dia x 21P) designed for a Bravo 2. I have not had a chance to do any testing with this set up and the prop does not hit the cavitation plate.

What is the impact of running such a large diameter prop? How does that diameter affect performance?

I also feel like a 21P is on the large side. I won't really have the easy ability to change props a lot so just thinking ahead, but I would expect a 19P for this set up and possibly a 17P?

Any input is appreciated. Thanks all.

 

[alldodge]

At the end of last year I bought a 1995 Rinker 265 Viesta Vee with a 5.7L (260 HP) I just realized she has a non-original Bravo One from a boat with a 7.4L as evidenced by the sticker on it. I also believe the prop is from a Bravo 2 based on part numbers I've been able to find on it-1946R21. I believe this is a QA1946R21 which is a huge prop (17.75 dia x 21P) designed for a Bravo 2. I have not had a chance to do any testing with this set up and the prop does not hit the cavitation plate.

What is the impact of running such a large diameter prop? How does that diameter affect performance?

I also feel like a 21P is on the large side. I won't really have the easy ability to change props a lot so just thinking ahead, but I would expect a 19P for this set up and possibly a 17P?

Any input is appreciated. Thanks all.

I don't see a B2 prop fitting on a B1 without coming in contact. Think there is a chance the drive is actually a B2?

What is your WOT now, are you getting 4800 rpm?

 

[muskyfins]

There's always a possibility on the Bravo 2, I'll try to get a closer look. Haven't had her WOT yet and won't be ready for shakedown splash until late May.

I did notice the serial number on the gimbal housing was ground out and a new stamped on it.....

 

[TexMonty]

As many others will chime in much more is needed, but my boat is a 4600 pound 24 foot deep V (Monterey 234 FS) and runs a 14 or 14.5D x 19 pitch - 5.0 merc with alpha I, 1.62 ratio - 48-49 MPH at 4800-5000 RPM. It sounds like you have not splashed it yet - do you know you gear ratio?

 

[muskyfins]

double checked. Definitely Bravo 1. As mentioned, new serial number stamped F300687. Can we identify this? I tried but to no avail. Prop has a lot of clearance but only measures about 16-1/2 dia. Pictures to follow.

 

[alldodge]

double checked. Definitely Bravo 1. As mentioned, new serial number stamped F300687. Can we identify this? I tried but to no avail. Prop has a lot of clearance but only measures about 16-1/2 dia. Pictures to follow.

It does check out as a B1 and being the diameter is 16.5 would clear. To checkout the serial number enter the number as 0F300687 (zero is first digit) at Mercruiser
https://www.mercurymarine.com/en/us/parts-and-accessories/parts-catalog

Or at Mercruiserparts http://www.mercruiserparts.com/selectSerailRange.asp?doc_nbr=BRAVO+ONE and yours would be the top line

 

[Bondo]

double checked. Definitely Bravo 1. As mentioned, new serial number stamped F300687. Can we identify this? I tried but to no avail. Prop has a lot of clearance but only measures about 16-1/2 dia. Pictures to follow.

Ayuh,.... The serial numbers are stamped in the Upper drive,.... All 3 Bravos use the Same Upper drive units,.....

Of the 3 Bravo lower units,....
The Bravo I, I believe you'll find is only 8" from prop shaft center, to the cav-plate, just like the Alphas, 'n Large gear case Merc outboards,.....
15.5" is 'bout all the prop they'll fit,...

The Bravo II lower units, swings a Massive, Huge prop, like for a houseboat or battleship,...
Which would be the 16.5", 'n 17.75" props mentioned here,....

'n of course, the Bravo III lower units run twin props,......

If in fact, the boat in yer avatar has a Bravo II lower unit on it,...
I'm thinkin' ya got screwed, as a Bravo I, or Bravo III is a better fit, for that hull,....

 

[alldodge]

Of the 3 Bravo lower units,....
The Bravo I, I believe you'll find is only 8" from prop shaft center, to the cav-plate, just like the Alphas, 'n Large gear case Merc outboards,.....
15.5" is 'bout all the prop they'll fit,...

I messed up again, don't know why I didn't go outside and measure my drives, it was raining. My B1 and B3 both have 8 1/8 to cavitation plate. Could replace the lower section with a B3 but then the props will cost around 1000, little less looking around

 

[muskyfins]

I'm starting to see what might have happened here. PO replaced original drive with Frankendrive. I'll have to measure to be sure, but looks like a B1 upper with a B2 lower. I was using redneck engineering, (forgot tape measure when I went to storage yard) but that prop is 16+" all day. With room to spare under cav plate. As for serial numbers-#1 scratched out/restamped (see picture) and #2- it hardly matters if the thing has been built from spare parts.

Why would you say that a B1 is better than the B2? Just additional drag?

And forget about prop set cost. Around here a B3 lower costs about how much I paid for this entire rig. Some day I want one, but not on this girl. Either try to make work as is or find a B1 lower.

 

[alldodge]

The B1 upper is used with all lowers (1, 2 and 3). Only thing that changes is the lower. You could get a B3 lower and it would fit right on what you have. You can look at Offshore Only in their classified section and find folks selling rebuilds and new, they also have a member for sell section

A B2 is not made for speed, made for power. The B2 will pull you out of the hole better then a B1 but not as good as a B3. As you mentioned it has a larger casing so more drag in the water.

On another note, seeing your corrosion going on. One thing which can be causing you some major problems is your bottom paint going clear up to your transom. There should be a one inch space of no paint (gelcoat only) separating the transom from the paint. Bottom paint has metals in them, mostly copper, which when it comes in contact with the transom turns into a large hunk of metal. The added metal makes your mercathode insufficient to keep corrosion at bay

 

[muskyfins]

I understand about all Bravo's having the same upper. I mentioned it as a B1 upper because it still has the original Bravo One sticker on it indicating it was originally used as a B1 (7.4 Litre even though this boat has a 5.7). I'm not against using it as B2 at least as a starting point. If it doesn't work out, by 4th of July, there's plenty of used B1's around for sale.

Yes-the anodes are in bad shape. New ones on their way. Boat goes to paint Saturday and will be removing a 1" gap around drive.

 

[alldodge]

Ok, sorry I misunderstood.
Here is something else I noticed and this happens all the time. Many folks remove the continuity wire from the bell housing to the drive (see pic). There should also be stainless steel wires going from the bell housing to the transom, and inside from the transom to the engine ground lug

 

[muskyfins]

So, while i was under the boat this weekend, the good news is I located the wire. See photo.

The bad news is I also found the old worn gimbal ring issue.:mad-new: That will have to go in a different thread.

 

[Tail_Gunner]

http://www.sterndrive.cc/Bravo.html

There's your b1 lower and there of good quality and with a 3 yr warranty cant beat that. They do need to be broken in however and so does a merc so who cares. I have a old 454 alpha combo that now is a 454/ SEI...two years going like a timex watch.

Dont b2's have bigger gears like 2.0???? instead of 1.5?

 

[alldodge]

So, while i was under the boat this weekend, the good news is I located the wire. See photo.

The bad news is I also found the old worn gimbal ring issue.:mad-new: That will have to go in a different thread.

At least they didn't remove the one going to the transom, just need to add one from that screw to the drive.

Sorry to hear about the gimbal

 

[muskyfins]

http://www.sterndrive.cc/Bravo.html

There's your b1 lower and there of good quality and with a 3 yr warranty cant beat that. They do need to be broken in however and so does a merc so who cares. I have a old 454 alpha combo that now is a 454/ SEI...two years going like a timex watch.

Dont b2's have bigger gears like 2.0???? instead of 1.5?

I though gear ratio was derived by driveshaft gears?

Although there is some old stamping in the sticker on the upper that says 220R. (remember this was/is a Bravo ONE upper) Is that a 2.2:1 ratio?:noidea:

 

[Tail_Gunner]

That would be a b3 upper... until futher notice that is. Which makes sense someone didnt like the b3 prop cost id be willing to bet...220 R 2.20 right hand rotation

 

[alldodge]

Bravo's don't have a right and left rotation. A bravo can run in either direction at full speed and load, just change the way the shift cable moves for F/R. Twin drives just changes the shift cable movement on one of them

 

[Tail_Gunner]

Bravo's don't have a right and left rotation. A bravo can run in either direction at full speed and load, just change the way the shift cable moves for F/R. Twin drives just changes the shift cable movement on one of them

So is it a b3 upper????

 

[alldodge]

So is it a b3 upper????

It is a B1 or Bravo upper. There are no B2 or B3 uppers, all use the same upper, only the lower is changed to make it a B1, 2 or 3.