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merc 525 motor

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Old 09-21-2010, 08:37 AM
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Default merc 525 motor

Any thoughts on when to freshen up these motors , have a friend with 350 hours on his . Iam hearing anywhere from 400-500 hours depending on how they are run and maintained .
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Old 09-21-2010, 10:05 AM
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Top end around 250-275 is what I have heard...and I have one in my boat!
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Old 09-21-2010, 10:44 AM
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I know it's not a 525 but I have a 500EFI that I did the top end at 280 hours now has 320.

I have to pull the motors to do some other work, what would be a good compression number or should I do a leak down test to see if they need freshened while out?
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Old 09-21-2010, 11:34 AM
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We did the top end on ours at about 280hrs and then ran close to 500hrs I think without a problem. We had the boat till 400 then sold it a friend. They're great motors!!
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Old 09-21-2010, 12:01 PM
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250-300 hrs on the top end, then 450-500 on the entire engine.

Wildman, do a leakdown test instead of comp. test. This will tell you more. Ideally, you want to see less than 10% leakage, but less than 20% is ok. If you have a cylinder leaking a good bit, then try to find out where it's coming from......intake valve, exhaust valve, or past the rings.
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Old 09-21-2010, 12:12 PM
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Had the top end of my engine done this past winter at 273 hrs (and went over the rest of it). All new parts were used during the rebuild which is the only way to go. There are ways to take short cuts during the "refreshening" and then there is the correct way to do it. Tell your buddy to find himself a good shop that will do it the right way if he goes through with it.
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Old 09-21-2010, 12:34 PM
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Also check the headers!!
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Old 09-21-2010, 01:17 PM
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Quote:
Originally Posted by Young Performance View Post
250-300 hrs on the top end, then 450-500 on the entire engine.

Wildman, do a leakdown test instead of comp. test. This will tell you more. Ideally, you want to see less than 10% leakage, but less than 20% is ok. If you have a cylinder leaking a good bit, then try to find out where it's coming from......intake valve, exhaust valve, or past the rings.
Eddie
Is that with a cold or warm motor?

I assume warm.
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Old 09-21-2010, 01:20 PM
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Quote:
Originally Posted by Wildman_grafix View Post
Is that with a cold or warm motor?

I assume warm.
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Old 09-21-2010, 01:52 PM
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What does a good top end rebuild AND a complete rebuild cost for a 525? For example, compared to buying new, are you looking at 30% cost? Thanks for the information in advance.
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