Vo 540 HP and RPM

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terrible ted
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Vo 540 HP and RPM

Post by terrible ted »

My 540 tag was 315 hp @ 3200 Helicopter motor
Now we increased the hp raise the compression over 2 points. But i have the prop set for 3000 rpms. I wonder what hp drop from 3000 to 2700? I probably be setting down to 2700 to conserve more fuel and give me a better cruse rpm. I wonder how much pitch that will be? I did this years ago i know there not much difference in performance as for top power but I did set it back to 3000. I do have some used mags now that I put on the pace maker. As far as I know they are not working.
fl cracker
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Re: Vo 540 HP and RPM

Post by fl cracker »

My AV 300 shows @2,575 RPM the hp is 290 . I would figure at @2,850 i would be 300+ but I don't know that to be a fact .
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kwanjangnihm
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Re: Vo 540 HP and RPM

Post by kwanjangnihm »

Ted is this the factory engine specs for your motor? Are you running 1 or 2 carbs now? If you bumped compression 2 points, are you running 11.0:1 CR pistons?

VO-540-C1A
315 @ 3200 100/100LL 8.70:1 High comp. altitude engine with two (2) MA-6-AA carburetors
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terrible ted
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Re: Vo 540 HP and RPM

Post by terrible ted »

original 7.? compression twin carb. Went to the 10 to 1 compression. original tag 315@3200, I looked it up once. The motor does have thump. Running one carb now. I can say it sucks fuel. I guess the really question is with the increases in pitch, does that offset the drop in hp to some extent? I believe it was twin ma5 carbs originally.
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Slidin Gator
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Re: Vo 540 HP and RPM

Post by Slidin Gator »

terrible ted wrote:
Mon Dec 14, 2020 2:28 pm
I guess the really question is with the increases in pitch, does that offset the drop in hp to some extent? I believe it was twin ma5 carbs originally.
No it does not. But 3,200 RPM is pretty far off the chart for efficiency of the prop and it must be loud. 2,800 should work well, lower rpm will sacrifice some power for lower fuel consumption.

I do wonder (assume) if the VIO cam is different from the IO cam for peak Hp at 3,200?? Not that a cam swap is quick or easy.
I still think I-10 is the Mason Dixon line.
2013 Mike Stossel Boats, 13' x 7' deck over, IO-540, 74" NGQ less winglets.
terrible ted
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Re: Vo 540 HP and RPM

Post by terrible ted »

I been told that my boats quit. I know wispertip said you must be pushing some hp for were the prop is set. Yea.i am looking to get better fuel thats why ihave a 74 inch wt, Now i think the quit is the motor exhaust tips point down toward the water, i just puton a pace maker. Dont know if that changed my rpm at all. Only run it twice a dcant see the display
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Slidin Gator
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Re: Vo 540 HP and RPM

Post by Slidin Gator »

Ted,

I just re-read your thread, I had mixed up the 3,200 helicopter rating Kwan posted vs. what I now see is your present 3,000 setting. 3,000 rpm is much more in line with reason for the prop. What pitch has you at 3,000 on the trailer?

Jacking up compression with no other mods increases torque but it takes head and cam work to make much use of the compression at top end. The engine gotsta breath, if it can't suck it in, it can't compress it (same logic applies to props).

I would not be surprised if you found the boat to work as well or better pitched down 100-200 rpms, I would be equally not surprised if it worked best right where you got er. :dontknow:

Grab the torque wrench next weekend and do some test and tune, I wanna know. :scratch:
I still think I-10 is the Mason Dixon line.
2013 Mike Stossel Boats, 13' x 7' deck over, IO-540, 74" NGQ less winglets.
terrible ted
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Re: Vo 540 HP and RPM

Post by terrible ted »

I will verify the position. I am off the seam line in the prop, Should be around 13 degrees. 74 inch wispertip. I may be working this week end on nuisance hog reduction. I also like to get a little fishing in.
terrible ted
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Re: Vo 540 HP and RPM

Post by terrible ted »

I will verify the position. I am off the seam line in the prop, Should be around 13 degrees. 74 inch wispertip. I may be working this week end on nuisance hog reduction. I also like to get a little fishing in.
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Re: Vo 540 HP and RPM

Post by terrible ted »

Sorry wife been in and out of the hospital haven had time to do anything. Now the roofing company's here yard access is blocked for a few days.
terrible ted
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Re: Vo 540 HP and RPM

Post by terrible ted »

So I set it about 2700 a little to early to tell completely about power. Now I may have a bad cylinder smoking a little on the driver side and its pushing oil out at top rpms.
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