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Estimated HP output - Build Sheet attached

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Estimated HP output - Build Sheet attached

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Old 04-09-2018, 09:18 PM
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Default Estimated HP output - Build Sheet attached

Hello all,

Looking to estimate power in order to reprop a boat. The basics include:
Carbed 502 Mag x 2
Each motor has recently been rebuilt with the following parts as well as Stainless Marine Exhaust

Any help would be appreciated.

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Old 04-09-2018, 10:14 PM
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It looks like pretty much a stock rebuild so I wouldn’t expect enough difference to need new props.
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Old 04-09-2018, 10:42 PM
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I believe these started off life as the 415HP 502s. This would be very disconcerting if they spent all this money just to keep it stock. From what I gather, they were trying to replicate the HP500 - do you think this build sheet supports that idea? Should this cam, IM, Heads, and exhaust get over 500HP?

Thank you.
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Old 04-10-2018, 12:27 AM
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I would think those pieces would have the potential to see around 500hp.
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Old 04-10-2018, 12:46 AM
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This is pretty close to the cam (I think his is on 114 lob sep) and its about the same as an 500EFI cam
https://www.summitracing.com/parts/crn-168761/overview/
Basically its a HP500 with Dart heads so probably 525-550hp depending on the tuning.
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Old 04-10-2018, 03:40 AM
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Dyno it. It's worth the money. Also make sure it's fully dressed in marine exhaust otherwise the power numbers will be dramatically skewed. You'll also know where it makes the best power which will make dialing in props even easier.
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Old 04-10-2018, 06:12 AM
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530-550hp depending on how good of a fluff and buff they do on the heads.
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Old 04-10-2018, 06:20 AM
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If you are going to spin the motors higher there may not be a need for different props.
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Old 04-10-2018, 07:20 AM
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Originally Posted by JRider View Post
If you are going to spin the motors higher there may not be a need for different props.
Thats another good point.

Thank you for your input guys. The motors are in the boat, so I don't think it's worth going for a dyno session yet.
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Old 04-10-2018, 08:01 PM
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I got 650 HP out of my 509's with 10 to 1 compression, ported Dart heads, hyd. roller Crane 741 cam and Lightning headers. lots of other tweaks " TINKERING "
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