propeller vs rpm question
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propeller vs rpm question
I am trying to help my brother with his 22' regal/velocity. I am confused with the way the boat has reacted to the three propellers we have tried so far. First prop is a 26P Bravo 1 4 blade. Strong mid range 4800 rpm max 73.7mph on gps. Easy to get on plane, strong mid range to the maximum observed 4800rpm. Second prop 28P Bravo 1 4 blade. Slower to get on plane (although not a problem),still strong mid range same 4800rpm max 78.0mph. Third prop is a Hydromotive 23P 4 blade (they told me the 26P Bravo 1 actually measures 25P) planes easy seems to slip in mid range 63.5mph at the same 4800rpm. The engine is a warmed over 454 that dyno'd at 545ft/lbs@4400rpm and 461hp@5100rpm. This was with a very lean carb that we later found out was due to a fuel supply problem, but I would think that the power peaks would be very close to the dyno rpm's. The question I would like to ask is why am I not seeing any rpm change with these various propellers. I am going to call Hydromotive tomorrow but would like to hear a few different points of view.
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Re: propeller vs rpm question
Rev limiter somewhere? Bad Tach, or are you using MSD box. I had problem 2 years ago. Motor would screem to 4800rpm & then fall flat. Talked to everyone & got all kinds of answers. Install friends MSD box & then motor ran to 5700 rpm, Put old box back on & 4800 again.
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Re: propeller vs rpm question
The ignition is a Crane unit with the rev limiter set at 6000rpm. We used the ignition during dyno testing. The tach is a brand new Autometer and I have hooked up my Mac Tools scan tool to verify the rpm. We have not changed the fuel pressure guage, but that is next. I don't think it is a fuel supply problem because we have warmed it up, installed new plugs and run it hard, shut it off and pulle them. We are rich by probably 2-3 jet sizes. Last night I was thinking some more about this and thought it may be the mufflers. These look like the type that belong on a cabin cruiser.They are 2' long 1' in diameter 4" id and made of fiberglass. I could not even find them on the internet. We are going to remove them and try again.
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Re: propeller vs rpm question
You did check & make sure the throttle blades open all the way? I would still get someone else ignition box & try it. Wire going to distributer is out by itself & not with other wires?