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Mercruiser hp 500 or other big block Merc motors

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Mercruiser hp 500 or other big block Merc motors

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Old 08-06-2005, 10:54 PM
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Default Mercruiser hp 500 or other big block Merc motors

What is considered high hours on Mercruiser motors. Also, with normal wear and tear, when should a motor like these be rebuilt????
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Old 08-07-2005, 08:31 AM
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Default Re: Mercruiser hp 500 or other big block Merc motors

Hp500's need top end work at 200hrs ...stock 454's can go a long time ...but any motor over 500 hours needs attention .... .02
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Old 08-07-2005, 08:54 AM
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Default Re: Mercruiser hp 500 or other big block Merc motors

500's ,,, yes, stock power,,, I dont agree.

I have a customer with a 38 Special with 502 MPI's at 1100 hours. Never been touched. He just blew his first clutch. Doing both drives to be safe.

Depends on maintenance and how the boat was used.
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Old 08-07-2005, 09:09 AM
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Default Re: Mercruiser hp 500 or other big block Merc motors

not all 500's, friend has 98 Formula with just over 500 hours. never touched until recently, bad roller lifters- springs were fine.
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Old 08-07-2005, 09:22 AM
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Talking Re: Mercruiser hp 500 or other big block Merc motors

Usually the lifters go bad because the spring pressures are to low and allows the lifter roller to lose contact with the camshaft lobe. They don't have to be broken to be bad.

I have had customers in the past with 350's, 454's and 502 that have logged well over 750 - 800 hours with regular maintnance.

It's all in how you run them and how good you take care of them. Plus it helps not to have twin smallblocks in a 40' 16000lb. cruiser also.

John

Last edited by Pwrbt33; 08-07-2005 at 09:26 AM.
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Old 08-07-2005, 01:27 PM
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Default Re: Mercruiser hp 500 or other big block Merc motors

Depends on maintenance and how the boat was used.
This is true. I don't think it matters how many hours unless you know how the boat was used during those hours. What if it's a poker run boat that spends most of its time at WOT; this equals lower hours before a rebuild is needed.

I am often asked how installing a supercharger will affect hours between rebuilds on these engines. If fuel and spark and cooling are right I think the supercharged engine has an advantage under most conditions. Which do you think is more stressed, a NA engine putting out 500 HP @ 5200 RPM or a SC engine putting out 500 HP at 3700 RPM and 3.5 psi of boost? Yes, cylinder pressures are higher but all other stresses related to piston speed and RPM are much lower.

Of course if you run it WOT and 800 HP all the time, you know the answer.

Last edited by tomcat; 08-07-2005 at 01:31 PM.
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Old 08-07-2005, 01:42 PM
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Default Re: Mercruiser hp 500 or other big block Merc motors

Originally Posted by tomcat
Which do you think is more stressed, a NA engine putting out 500 HP @ 5200 RPM or a SC engine putting out 500 HP at 3700 RPM and 3.5 psi of boost? Yes, cylinder pressures are higher but all other stresses related to piston speed and RPM are much lower.

Of course if you run it WOT and 800 HP all the time, you know the answer.

i thought I had you until the redirect at the end!
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