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Mercury Racing blue motors: 500EFI, 525 EFI, 575 SCI. Pros/cons/maintenance/etc.

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Mercury Racing blue motors: 500EFI, 525 EFI, 575 SCI. Pros/cons/maintenance/etc.

Old 02-20-2011, 11:01 AM
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Originally Posted by thirdchildhood
Here's the read-out I got with mine when I bought the engine: Hmm, I just noticed that there is a "clear run history" box in the lower right............
This screen shot is taken from the CDS. It's a prime example of engine speeds being able to "go faster" than the limiter says once in a while. It's not that big of a deal to me unless you see lots and lots of instances.

The Clear History button you see will erase the RPM History but it will NEVER clear run time hours.

There are several reasons for wanting to clear RPM History but it also means you don't have this accurate history when you sell or buy the engine.

That would also be the case if a guy had to switch an ecu out or something..

The way to tell what you have is to simply add up all the different numbers in the RPM History column and compare that total to the "Run Time Hours". If they don't match, you know the mechanic or owner has cleared it some number of times..
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Old 02-20-2011, 11:03 AM
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And the above ecu has never had the rpm history wiped... It adds up perfect.
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Old 07-11-2012, 11:52 PM
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I know that this is a old Post but man the 500 hr mark is definitly true! I had 535 hours on my 500EFI and blew a head gasket.....It was running a solid 5150 rpm when #1 cylinder poked thru the head gasket and into #3 cylinder.... $$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$$ $
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Old 07-12-2012, 06:39 AM
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Originally Posted by MILD THUNDER
I have my own school of thought on that. Lots of people think EFI is the answer to all their problems. Now dont get me wrong, EFI is nice. And i am all for new technology.

However, there is absolutly nothing wrong with a carbureted engine. 90% of the guys out there you see with motors loading up, stalling, etc, is a matter of wrong carb tuning. I have supercharged engines, with a much more agressive cams than pretty much any blue motor out there, and never have i had the engines load up from idling too long, etc. I blip the key and they fire instantly. Sure on a cold morning, i may have to idle them up for 20 seconds or so because i dont have chokes, but reallly not a big deal.

Once a carb is setup properly, they can give many seasons of turn key performance. And, easier to modify to accept engine upgrades.

I also know of several people i boat with with merc blue engines that have had more issues sending their ecu's back in, and trying to get programming right, etc etc. I cant tune a ecu at the dock, but i sure can tune a carb at the dock.

So being a do-it-yourselfer, i prefer carbs. Especially on a non-stock engine. Problem is these days, not many mechanics/marinas have anyone knowledgable with carbs.
I was on the border about carb vs. EFI and I am more than happy pulling the trigger on my boat with carbs. No injectors, no computers and she fires right up.. Only have one choke for the 2 carbs. Like, said, I idle up for about 20 seconds on a cold start and then shes ready to go. As far as boats and the costs incurred, I will probably stick to carbs even in future boat buys...
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Old 07-12-2012, 07:22 AM
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Originally Posted by sleev-les
I was on the border about carb vs. EFI and I am more than happy pulling the trigger on my boat with carbs. No injectors, no computers and she fires right up.. Only have one choke for the 2 carbs. Like, said, I idle up for about 20 seconds on a cold start and then shes ready to go. As far as boats and the costs incurred, I will probably stick to carbs even in future boat buys...
I'd get rid of the choke and cut off the choke housings for better flow.
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Old 07-12-2012, 07:33 AM
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Originally Posted by thirdchildhood
I'd get rid of the choke and cut off the choke housings for better flow.
I'd keep the chokes. This is a factory merc 600sc setup with twin 700 holleys . Milling the choke towers off won't do much for performance. If its working well as is and idling nice with that big blower, leave it be. Enjoy the easy cold starts and fast idle function

Last edited by MILD THUNDER; 07-12-2012 at 07:44 AM.
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Old 07-12-2012, 07:48 AM
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Originally Posted by thirdchildhood
I'd get rid of the choke and cut off the choke housings for better flow.
Originally Posted by MILD THUNDER
I'd keep the chokes. This is a factory merc 600sc setup with twin 700 holleys . Milling the choke towers off won't do much for performance. If its working well as is and idling nice with that big blower, leave it be. Enjoy the easy cold starts and fast idle function
Exactly. I have no problems with it as is. Fires right up, runs great. I have minimum hunting at idle with the blower.
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Old 12-09-2013, 08:26 PM
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The 496 mag is bullet proof.in.my.opinion
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Old 02-01-2014, 04:34 PM
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My 500's are getting up to 400 hrs and thinking of refreshing them up with all parts including better springs but would anyone recommend different camshafts as I am looking for a little more power . My biggest concern is reliability more then speed even though speed is great too. Anyone have any recommendation what I should do or just stay with stock parts.
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Old 09-02-2015, 02:58 PM
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What's the best Valve Spring for Merc 500EFI ?
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