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Old 12-22-2014, 09:50 AM   #21
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without knowing the rated max rpm of that engine from the engine info plate and what rpm you are propped for any answer could lead you to running too hard.
We don't know how you are propped so anyone else's data is useless at this point.
Get those numbers and report back.
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Old 12-22-2014, 10:12 AM   #22
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Quote:
Originally Posted by psneeld View Post
Agreed.... my charts say 1200 rpm should only be about 1.0 GPH...

3.0 GPH shouldn't occur till over 2000 rpm which my boat has proven to me.

I plan on cruising around 1600-1700 RPM so I get slightly less than 2.0 GPH and hopefully somewhere's around 6.5-7.0 knots and average around 4.0 NMPG
THat's pretty much like my numbers.

1500 rpms 1.5 gal/hr 6.2 kts
1600 1.6 to 1.7 6.5
1700 1.7 6.8
1800 1.9 - 2.0 7.2
2000 2.5 7.8

these numbers are plus or minus 0.05%

Also I have a 4 bladed prop instead of the standard 3

SP135 Ford Manual has max torque between 1600 and 1800 rpms in a pretty flat curve
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Old 12-22-2014, 10:47 AM   #23
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Your fuel consumption at any specific rpm will be meaningless unless you're propped to the same WOT rpm as the compared boat and then the hull drag of the boat is yet another variable.
I have a friend who has the standard overpropped Willard 30 and he cruises at just about the same speed I do but at hundreds of rpm less. The same fuel burn though .. as would be expected.
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Old 12-22-2014, 11:05 AM   #24
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Quote:
Originally Posted by Wxx3 View Post
THat's pretty much like my numbers.

1500 rpms 1.5 gal/hr 6.2 kts
1600 1.6 to 1.7 6.5
1700 1.7 6.8
1800 1.9 - 2.0 7.2
2000 2.5 7.8

these numbers are plus or minus 0.05%

Also I have a 4 bladed prop instead of the standard 3

SP135 Ford Manual has max torque between 1600 and 1800 rpms in a pretty flat curve
Your rpm numbers compared to speed seem unusual. As rpm and speed increase, one expects to see more prop slippage. Normally you expect a slightly to significantly lower increment of speed increase for every additional 100 rpm. Yet yours remain constant and actually increases between 1700 and 1800 rpm. Any thoughts as to why?

Ted
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