I'm new at this and have a prop question?

[chevydog66]

My neighbor has a 89 Rinker 236 captiva, it used to have a 454 mag that gpsed at 68 mph. It now has a 540 that put out 565hp and 594 tq. on the dyno. We have tried a 24 and 27p 3 blade last year and can't get above 69 mph. I can't remember what rpm we obtained though. I will get that info soon, since our last test runs were last summer. I do remember that we were ventilating both props upon takeoff and also at a 35 mph cruising speed and then stabbing the throttle. A friend of mine recommends a 24 4 blade. What's your suggestion BBlades?

[bbladesprops]

Sorry for the delay!

A 4 blade may be needed to hook up better. If a rev limiter is in play, it could be causing the top speed problem.

If you have some new rpm vs. speed numbers, we will be able to better determine the best options. Also, we have test props to get us started.

[chevydog66]

OK, Correction. The old 454 gps at 62mph, with the same prop that it has on it now. I have ran the boat a few times and have learned this much. The 3 blade prop that is on it now was a 21, but it has been reworked to a 24, because it also has a 24 stamped in it. With 1/2 to 3/4 tank of gas and 4 people I was able to get the boat up to 68mph at 5800rpm, at WOT, on the gps. The 540 has a MSD marine ignition system in it, with a 6000rpm limiter chip. On the dyno the 540 put out it's best #'s at 5400rpm. I don't see a reason to spin it above 6000rpm, do you? I think the hull design is also a limiting factor. What prop are you thinking? Thanks!!

[Griff]

I would try a 25" Mirage plus and a 26" Bravo 1. Its gonna hard to get lead you in any real direction without a good base number from a known pitch prop.
Generally a prop can only be reworked 1" of pitch up or down, so its tough to tell exactly what you have now.

[chevydog66]

Yep, that's what I have heard. I guess I need to send it to a prop guy in order to have it checked to see exactly what it is. The prop that's on it now is a Mirage Quicksilver.

[bbladesprops]

I also like the 25 M+ test idea.

Call us and we can set up a trial propeller.

Keep the R's in the mid 5000 range.

[chevydog66]

Ok, I'm back with an update. I purchased a Bravo 1 24p 4 blade and ran it. It gps at only 66mph and 5200rpm, with 4 people, 2 coolers and 3/8 tank of fuel. A friend of mine has a 4 blade 22p, that he says will help bring the rpm's and mph up, because he wants to try my 24p 4 blade. He's runnin it on a Crownline 232 w/a 502" motor. So there's a baseline. Any ideas?

[bbladesprops]

It does seem somewhat strange that you could only get to 66 and 5200 with the 24 when you saw larger numbers earlier. Your slip numbers are OK.

The 22 will bring you to 5600+ rpm but the speed will only rise if the HP also continues to climb at a exagerated rate.

[chevydog66]

Ok, I tried another prop last weekend. It was a 23p Mirage and got 5200rpm at 69mph on the gps. I was hoping for 70+, but you know how that goes. It would slip just before being on plane, so I would have to pull back the throttle a little, then some trim. That was with 2 people and 3/8 tank of gas, and 2 cases of beer in the cooler. So now what? I think I need to be around 5400-5800rpm. Thanks BBlades!! One of these days I will call ya.