Pitch and Tachometer Verify and Get It Right !!!

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White Hawk
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Pitch and Tachometer Verify and Get It Right !!!

Post by White Hawk »

For those of you who do not know this already many of the tachometers that we use are not accurate. All of our motors have a sweet spot and the sweet spot can be identified by RPM. For those of you who do not know when you adjust your prop to add or remove pitch we are looking for that desired sweet spot and verify our progress with our tachometers whether it be higher or lower. I recently had my motor hooked up to a laptop which runs tuning software. The technician suggested that we verify the accuracy of my tachometer and in doing so we found out that it was off 100 RPM at Idle and 400 off at 5400. Long story short I was only really spinning 5000 when I thought it was at 5400. I then set my prop to a degree that allowed me to get 5800 RPM so now I was actually getting 5400-5500. The boat came alive! Crisp throttle response throughout the whole RPM range. Better bottom end, more responsive mid-range and a way faster top end. My fuel economy even got better. I found it hard to believe that I never thought to verify the accuracy of my tachometer. I could not believe how much I gained, I had been searching for the sweet spot for a year and never happy with my results. Now I know why my boat was not performing like I thought it should. If you get the chance you should verify your tachometer reading, it may be over it may be under but in both cases you will benefit from knowing. Enjoy the ride I'll see you out there.... White Hawk! :florida: :florida:
"The object of war is not to die for your country but to make the other bastard die for his." :florida:
Gary S
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Re: Pitch and Tachometer Verify and Get It Right !!!

Post by Gary S »

Are we talking electronic tach or mechanical?
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White Hawk
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Re: Pitch and Tachometer Verify and Get It Right !!!

Post by White Hawk »

I am not sure if there is deviation in both? Perhaps there is someone with the technical knowledge who might weigh in. I do know the extra 400 RPM brought the pitch to the sweet spot that I had been searching for.
"The object of war is not to die for your country but to make the other bastard die for his." :florida:
Gary S
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Re: Pitch and Tachometer Verify and Get It Right !!!

Post by Gary S »

Are you using a mechanical tach?
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Slidin Gator
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Re: Pitch and Tachometer Verify and Get It Right !!!

Post by Slidin Gator »

Whitehawk,

Thanks for the reminder, I find mechanical tachs to be easily off by 100-200 RPM. Electronic tachs certainly have their failure modes, but it's not normally in the small range (200-400 RPM off at WOT). Where I do run mechanical tachs I calibrate against a digital tach for tuning.
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.
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White Hawk
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Re: Pitch and Tachometer Verify and Get It Right !!!

Post by White Hawk »

I find it hard to believe that 400 RPM correction has made such a huge difference. I have a great cruise, great response and improved fuel economy and top end. I have found the sweet spot!
:florida:
"The object of war is not to die for your country but to make the other bastard die for his." :florida:
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