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Mercury 565 Actual HP?

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Old 04-17-2021 | 01:19 PM
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Originally Posted by Eddienel
Is that the front of the crank or the back?(joking) Whatever it is I want one!
Could be your Lucky day Eddie. I'm considering selling my twin 565's and replacing with bigger power
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Old 04-17-2021 | 02:32 PM
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Originally Posted by thirdchildhood
Yep, it sure does. I looked in my 525 service manual and it also says 525 hp rated at crankshaft. Hmmm.
But, the 525s are known to be closer to 540hp, so probably actual close to 525 at the prop through a bravo.
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Old 04-18-2021 | 09:09 AM
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The difference is due correction factors being different depending on the standard used.

Mercs are rated at a more conservative standard than your normal aftermarket Dyno shop. And that’s assuming the Dyno operator even uses those corrections properly. The difference is 4-7% I believe, I don’t remember exactly.

A 565 likely makes 600 on a normal aftermarket engine Dyno test.
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Old 04-19-2021 | 01:17 PM
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Originally Posted by hogie roll
The difference is due correction factors being different depending on the standard used.

Mercs are rated at a more conservative standard than your normal aftermarket Dyno shop. And that’s assuming the Dyno operator even uses those corrections properly. The difference is 4-7% I believe, I don’t remember exactly.

A 565 likely makes 600 on a normal aftermarket engine Dyno test.
600 hp sounds about right to me. It's 533 CID with dual throttle bodies. I don't know what other differences there are between the 525 and 565.
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Old 04-19-2021 | 03:41 PM
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I've heard Mercury takes the #8 spark plug wire off during dyno.....
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