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454 Compression Issue

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Old 01-24-2012, 03:01 AM
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Default 454 Compression Issue

Hey guys, jumping back into the boating scene but I wanted to make sure I don't make a mistake on this boat I want to buy....
It has mid 80's vintage 454's with about 650hrs on them. We did a compression check and one motor is running 125 - 130psi on all cylinders, pretty good for its age, but the other is 125 or so on most cylinders but #3 and #6 are at 105 and #8 is 115

It still meets the 70% spec + over 100psi minimum Mercruiser calls for but seems borderline to me.

Any of your thoughts or comments would be appreciated.

Thanks
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Old 01-24-2012, 04:47 AM
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thats common with that many hours,a valve job& new valve springs would be in order,but a complete rebuild would be the way to go,price it accordingly!
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Old 01-24-2012, 07:49 AM
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I would do a leak down test, it's more accurate and will give you a better idea of what needs work.
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Old 01-24-2012, 09:23 AM
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Just sounds to me like they are tired. 650 hours, many years, sounds like its close to freshen up time. Also a good time for upgrades!!

I find that sometimes, if you price the purchase price accordingly, its the way to go. Have the engines gone thru, then you know what you have and your good to go for a while. Beats paying top dollar and having a engine puke right after you buy it.
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Old 01-28-2012, 08:27 AM
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Thanks guys for all the input, much appreciated.
It seems to rebuild a old school 454 like this runs between 6-8k. The marine dealer selling it was trying to tell me 3-4k ..doesn't sound right when labor to derig and reinstall runs about 16-18. Hrs @ $99/hr....
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Old 01-28-2012, 01:50 PM
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Originally Posted by PowerstrokeNC View Post
Thanks guys for all the input, much appreciated.
It seems to rebuild a old school 454 like this runs between 6-8k. The marine dealer selling it was trying to tell me 3-4k ..doesn't sound right when labor to derig and reinstall runs about 16-18. Hrs @ $99/hr....
Wow. Now I know why I do it all myself.
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Old 01-28-2012, 08:29 PM
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PS,
With that much age and that many hours on them, I would expect a lot of corrosion in the water jackets in the block, heads and manifolds. I reworked a set of heads on a similar vintage MPI engine for a friend of mine last summer and I swear I will never do it again There was so much corrosion I have to cut 4 or 5 of the head bolts off. He brought the engine to me on a cradle and it was still a lot of work. If he was a regular paying customer the bill probably would have been at least $1400, and I did absolutley nothing the bottom end. It turned out ok, but if your engines are anywhere near the same, I would price a pair of Mercruiser remans with manifolds and bargain on the purchase accordingly.

Just my opinion,
Bill Koustenis
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Waldorf Md
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Old 01-30-2012, 04:18 AM
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Originally Posted by BillK View Post
PS,
With that much age and that many hours on them, I would expect a lot of corrosion in the water jackets in the block, heads and manifolds. I reworked a set of heads on a similar vintage MPI engine for a friend of mine last summer and I swear I will never do it again There was so much corrosion I have to cut 4 or 5 of the head bolts off. He brought the engine to me on a cradle and it was still a lot of work. If he was a regular paying customer the bill probably would have been at least $1400, and I did absolutley nothing the bottom end. It turned out ok, but if your engines are anywhere near the same, I would price a pair of Mercruiser remans with manifolds and bargain on the purchase accordingly.

Just my opinion,
Bill Koustenis
Advanced Automotive Machine
Waldorf Md
exactly
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