Bravo 3
 

Not having much luck finding info on prop timing a Bravo 3. I have found some info on timing a 3/3 prop configuration but nothing on a 4/3 configuration. Is it necessary to time a 4/3 prop configuration or not.

I have pics up here all about this. Search for it.

I just spent the last 35 min scanning your last 950 posts, I did a search for this and I didn't find what I was looking for.
But thank you for your help anyway.

Short answer: I don't *know* if it is important. But I *think* it is worth doing.

That said, my understanding of both Volvo and Merc counter-rotating-prop timing is that the timing's intent is to avoid/minimize blade-overlap in the 12-o'clock position, directly under the cavitation plate.

If that understanding is correct, you can work through the geometry to minimize blade overlap at that 12 o'clock (0 degrees) location. I just rushed through it on the back of an envelope but if I did the math right, the best you can do will have blade overlap nearest the 12 o'clock spot occur at 22.5 degrees, 7.5 degrees, and negative 7.5 degrees. Shifting the orientation will make one of those 3 overlap locations even closer to 12 o'clock (0 degrees), or smaller than 7.5 degrees. So, I think the best you can do is to ensure the closest overlap position is at least 7.5 degrees away from right below the center of the cav plate.

I was rushing, but I *think* I got the math right. Easy enough to be sure by drawing it up I think.

It's much easier of course with a 3/3 blade propset, since they are symmetric and the phase of overlaps is evenly split, not drifting over the course of a revolution . Properly installed, a 3/3 set should see peak blade overlap that is always at least 30 degrees from the 12-o'clock spot.
Mike

Call bBlades and ask them -

Thanks Ghost24, your math seems about right. I actually checked it on the outdrive.
I found plenty of info. on the 3/3 propset but nothing on the 4/3 propset. I assumed with the extra blade "timing" is not as critical.

If the reason for timing is a vibration or loading (or something) issue based on overlap at the cav plate, I would install by putting the 4-blade on with two of its four blade centers at 45 degrees and minus 45 degrees, and with one of the three-blades centers straight up at zero degrees.

Post 31 here and some info written thru the thread.

The pic I had to send to Artie cause I do not know how to post pics up here.

Its a Volvo DP but does not matter been doing all twin prop apps this way since the 90's.

http://www.offshoreonly.com/forums/g...r-drive-4.html