2008 Formula 34 PC prop issue?


F

FormulaLP

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My boat has Mercruiser 496?s with Bravo 3 outdrives. My outdrive gear ratio is 2.0:1. The altitude I?m boating in is about 3600 feet. I have 24 pitch props. That is the right set up for this boat per Formula. The boat is sluggish getting on plane. And WOT is about 4300 RPM?s. Any thoughts?
 
I just sold a 2008 34' Pc with 496 Bravo 3 and never had a problem getting on plane.
The WOT should be more like 4600 - 4800
The pitch sound right of the to of my head.
Do a compression test make sure all cylinders are good, That is were I would start
Send out the fuel injectors to be tested and cleaned, When I did mine to were 20 % clogged.
 
My 2008 34PC was delivered to 1st owner (Possum Kingdom Lake, TX) with 22p props. I tried the 24p props to see if economy was better. Im much happier with the performance of the 22p.
I boat at sea level. LI Sound.
 
I think it's pretty simple...you're over propped I would try a pair 22.

Ideally get the 4 x 3 blades up vs standard 3 x 3

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The compression is good, plugs are good and we’re going to check the injectors. 22 pitch props seem like the answer. But top end is poor as it is. Top speed is about 34 MPH. Does that sound right.
 
WOT is 4300 and that speed is about 34 MHP. If the boat is over propped the the RPM’s will come up but not the speed. I’m at a loss and so is my mechanic. The 22 pitch prop would get it out of the water better but the top performance seems off. The mechanic is suggesting changing the gearing. I love the boat but I’m disappointed in the performance.
 
I haven?t had this boat for long. I have twin 496 Mags with bravo 3 outdrives (2.0:1) gear ratio. I have the factory recommended 24 pitch props. I?m boating at 3600? elevation. Per Formula this is as it should be. I use the trim tabs to get on plane and it takes quite a while still. Without the trim tabs it takes a long time at wide open throttle. When I get on plane I can only get 4300 RPM with WOT. WOT top speed is about 34 MPH. The most economical RPM is about 3800, speed is approx 27 MPH. Miles per gallon were approx 38. I can drop prop pitch to help get out of the water but lose top end speed. So.... my question is, how does this compare to other similar PC?s. Are my expectations to high. Because I expected better performance. Any help would be great. Formula suggested checking compression. Both engines are right where they?re supposed to be. Thanks
 
At 3600 there would be less HP but not sure as much as the boat appears to be showing. The 496 WOT should be 4400-4800, the HO is 4600-5000

Maybe do a good physical on the motors, Compression, Leak down, misfire test, fuel pressure, TB opening to 100%, TB voltage correct, MAP volts kPa
 
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I forgot I required sharing access but I think you should be all set now

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Thank you, I got the spreadsheet. It’s looking like going to 22 pitch props is a good starting point. Should I go with 4/4 or 4/3? Any preference?
 
I honestly don't know if it's going to be that significant I would say whatever you can find at the best Price others might disagree but I'm sure folks will chime in

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Its all about IF you can reach WOT rpm. The more blades the more it takes to turn because the reduction in slip. Turning 24 3-blade gives you X-rpms at WOT. Going to 22 will increase the rpms, going to 4 blade 22 will not allow the same increase.

If you want to go 4x4, contact Hill marine directly and they will swap props as many times as needed and only cost is return ship each time
 
FormulaLP said:
Thank you, I got the spreadsheet. It’s looking like going to 22 pitch props is a good starting point. Should I go with 4/4 or 4/3? Any preference?
Click to expand...

I assume your tabs were pulled up to neutral on your run? Also did you have the drives trimmed out at all? I find that with mine a little trim tends to free the hull up quite a bit and turn more rpm. I am coming out of the performance boat realm (22 Years) so the Bravo 3 props are new to me.
 
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My 34' has the 454 MPI's, 3,400 RPM is 32 MPH on GPS. I also have the 24 pitch props on my Bravo 3's.
 
I had a perfect day to check out the boat. I lowered the trim tabs to get on plane. I ran the boat at WOT. I had it trimmed to where it was running at its peak. More trim and it would begin to cavitate and less would loose RPM.
I believe I will have to go with the 22 pitch props. My mechanic is giving me a price to change the gear ratio. I'm not sure what the difference would be. Change gear ratio or change props...... The 2.0:1 is what Formula suggests for this altitude & that's what I have.
I'll keep you posted on the gear change scenario. Any thoughts are welcome.
 
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