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HELP !!! My Merc 525 EFIs are over revving !!!

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HELP !!! My Merc 525 EFIs are over revving !!!

Old 09-06-2021, 08:40 AM
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1. OE style rocker arms 250-400 per engine
2. push rods 150-200 per engine
3. valve springs 200-400 per engine

#4 which you should of done IMO is lifters 400-600 per engine

BTW push rods are in the heads. there the long round skinny things that make the valves go up and down......
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Old 09-06-2021, 09:38 AM
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Wait a min, you have 560 hours on these engines and had pushrods, rocker arms and valve springs replaced? No lifters, no valve job, no head gaskets?
And you’re planning to repower next season? You wasted your money this year.
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Old 09-06-2021, 10:39 AM
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Getting rid of waterlogged wood drops a lot of weight off the boat. That alone could give you the rpm gain. Also putting in new valve springs can increase performance if the old were truly fatigued and allowing valve float.
As long as the compression is good on all cylinders I don't see why one would think he wasted his money. Those short blocks should be good for double what he has on them. Especially with 20hr oil & filter changes. And it certainly doesn't sound like he abuses them.
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Old 09-06-2021, 12:23 PM
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Originally Posted by Unlimited jd View Post
Wait a min, you have 560 hours on these engines and had pushrods, rocker arms and valve springs replaced? No lifters, no valve job, no head gaskets?
And you’re planning to repower next season? You wasted your money this year.
yes sorry lifters we’re changed and gaskets. And yes I’d like to repower next year but figured in case I have to push the expense off another season, I wanted to be sure I was not going to grenade my engines. If I can afford to drop 560’s in, I’d just sell my 525’s cuz there in perfect shape and pasted all the tests with flying colors 😎
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Old 09-06-2021, 12:30 PM
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another 300 bucks for a valve job while the heads were off would of been money well spent,

Last edited by F-2 Speedy; 09-06-2021 at 03:21 PM.
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Old 09-06-2021, 01:42 PM
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Originally Posted by Smitty275 View Post
Getting rid of waterlogged wood drops a lot of weight off the boat. That alone could give you the rpm gain. Also putting in new valve springs can increase performance if the old were truly fatigued and allowing valve float.
As long as the compression is good on all cylinders I don't see why one would think he wasted his money. Those short blocks should be good for double what he has on them. Especially with 20hr oil & filter changes. And it certainly doesn't sound like he abuses them.
All good points and yes I rarely beat the boat and the compression is bang on where it needs to be. The DDT test when I pitched the boat 9 years back showed that the majority of the 212 hrs on the boat were idle, cruising and only 8 hours at 5200 so the engines were truly babied when I got it and rarely beaten since I’ve owned it. Don’t get me wrong, I drive it hard but it’s well maintained 😎

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Old 09-06-2021, 02:01 PM
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good luck on the test run tomorrow
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Old 09-06-2021, 02:29 PM
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Originally Posted by Smitty275 View Post
Getting rid of waterlogged wood drops a lot of weight off the boat. That alone could give you the rpm gain. Also putting in new valve springs can increase performance if the old were truly fatigued and allowing valve float.
As long as the compression is good on all cylinders I don't see why one would think he wasted his money. Those short blocks should be good for double what he has on them. Especially with 20hr oil & filter changes. And it certainly doesn't sound like he abuses them.
500 and 525 lifters fail on the regular around 300 hours. Skipping the valve job isn’t that big of a deal, if he skipped on the lifters it would be just as close to having a failure as when he started spending all that money. But since they were replaced I retract my wasted money comment and agree, a little maintenance now, and sell them still running next year. I hope to do the same with my 525’s
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Old 09-06-2021, 09:47 PM
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Originally Posted by F-2 Speedy View Post
good luck on the test run tomorrow
Might not splash it tomorrow, I had a small crack on one if the headers that created a small leak and a replacement was ordered from the US. And apparently being overnighted to Montreal. If it lands here tomorrow, then No problem since he left the damaged one off making it a quick repair……just more frikkin money…..and time 🙄

i’ll keep ya’ll posted 😁



Last edited by Barryama1124; 09-06-2021 at 09:52 PM.
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Old 09-06-2021, 09:54 PM
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Originally Posted by Barryama1124 View Post
Might not splash it tomorrow, I had a small crack on one if the headers that created a small leak and a replacement was ordered from the US. And apparently being overnighted to Montreal. If it lands here tomorrow, then No problem since he left the damaged one off making it a quick repair……just more frikkin money…..and time 🙄

i’ll keep ya’ll posted 😁

Interior before

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