Sea Ray BR 210 prop selection results

[cptnmcluvin]

I wanted to provide a follow up for this thread.

http://forums.iboats.com/prop-questions-topics/sea-ray-br-210-prop-selection-problems-568994.html

This summer we upgraded the SeaRay BR 210 from a 3 blade 21 pitch prop to a 4 blade 20 pitch prop.
The results were successful. Hole shot and watersports towing were much improved.
The Merc 5.0 engine even sounds better with the 4 blade prop.
However, the 20 pitch prop is still a little too tall for optimal wakeboarding.
Again, the 20 pitch is much better for wakeboarding than the 21 pitch was.
Cruising rpms and mph were about the same.
We never drive much over 30 mph so the top end performance is not relevant for our use.
Which brings up the point that we never red line our boats and don't plan to.
I may be technically incorrect but the idea of red lining the boat to test a prop does not appeal to me.
When you buy car tires, do you drive 150 mph to determine if they work?
Yes, I realize the WOT performance test can help determine if a prop takes the motor out of normal rpm ranges.
Despite what everybody says I'll stick with the 0 to 30 mph test results.

 

[steelespike]

Re: Sea Ray BR 210 prop selection results

In the case of testing tires there is no need as they have already been rated.
You don't necessarily have to redline to get meaningful results.
but you need to know exactly where your propped for at wot perhaps it might be a couple of hundred below max rpm
or at the rating or sometimes in the course of events a little over the max.
When propping at a little more than 60% of max speed you might be several hundred rpm off.
When propped for water sports your not likely to be lugging the motor but you may be wasting rpm.
Also without a wot test you can't know if there are any issues with your setup.
Its not out of the question that a person who props by 60% of power could even be down on power and not realize because it performs
well in his or her range as propped.

 

[jestor68]

Re: Sea Ray BR 210 prop selection results

If you prop your boat so that the engine cannot attain the minimum rated rpm, you're "lugging"it and the engine will not produce normal power at any speed(look at a hp/torque graph).

If you prop it so that the engine over speeds excessively, that is obviously bad.

The ideal water sports set up would be to prop it to attain max(or slightly over) rpm. This will give the best pull and speed holding at wake boarding speeds.

This is the protocol that the entire marine industry follows. If you choose to use some other technique, it's your boat.

 

[theBrownskull]

Re: Sea Ray BR 210 prop selection results

I understand why you want to treat the motor with respect but like the others have stated a WOT test is the best way to find the operating performance. Lugging an engine over time can do damage. I switched from a 19 pitch aluminum to a 19 pitch stainless and it performed fine but the engine was below the WOT operating rpm's. I then tried a 17 pitch and "bang" I could tell the difference. Hole shot was better and the engine operated at 4800-4900 rpm..right about in the middle of the WOT rpm range.