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Seller claims 454 Magnum 420hp stock - really?

Old 09-17-2015, 01:41 PM
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Default Seller claims 454 Magnum 420hp stock - really?

Hi. I'm looking at a '79 Formula 233 this weekend. The seller says it has a 1996 or 1998 FWC 420hp stock 454 Magnum repowered in 2012 and a new Bravo 3. When I look up the serial number, I get 1997 MERCRUISER 3.0LX ALPHA so I'm confused. See attached for photos. Is it really a 454 Magnum with 420hp? Is it Gen V or VI? See attached for pictures.

There are 500 hrs on the engine, and he claims to have changed motor and drive oil every 80 hrs. If true, what kind of longevity should I expect and when should I expect to rebuild?

Thanks!

http://imgur.com/a/IbdIE



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Old 09-17-2015, 02:24 PM
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Sure looks like a 365 hp to me ...
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Old 09-17-2015, 02:38 PM
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I think Merc did make a 420hp 454 at some point but don't think this is it. It looks like the 365 or later 385hp version to me too.
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Old 09-17-2015, 02:41 PM
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Flame arrestor cover means nothing if engines been replaced or rebuilt.

Get some documentation !

BTW; If I remember right, the 420 had Gill Exhaust and a Weiand Single Plane Intake and a Holley carb. Could be wrong, been many years.
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Old 09-17-2015, 03:23 PM
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Originally Posted by SB
Flame arrestor cover means nothing if engines been replaced or rebuilt.

Get some documentation !
Yes. This is my concern as well. From the picture above, do you think I'll likely be able to see the engine code stamped on the back? I'm doubtful even with my camera phone and mirror.

http://www.marinemechanic.com/merc/d...lockcodes1.PDF
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Old 09-17-2015, 03:29 PM
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The 420 had Gil exhaust and could either have a Weiand single plane intake or a GM dual plane. Pop the oil cap off and look at the rockers. A 420 should have Crane gold rockers, a mag will have stamped rockers. Nothing about that engine looks like a 420.
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Old 09-17-2015, 03:31 PM
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Originally Posted by SB
Flame arrestor cover means nothing if engines been replaced or rebuilt.

Get some documentation !
Yes. This is my concern as well. From the picture above, do you think I'll likely be able to see the engine code stamped on the back? I'm doubtful even with my camera phone and mirror.

http://www.marinemechanic.com/merc/d...lockcodes1.PDF
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Old 09-17-2015, 03:36 PM
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Originally Posted by SB
Flame arrestor cover means nothing if engines been replaced or rebuilt.

Get some documentation !
Yes. This is my concern as well. From the picture above, do you think I'll likely be able to see the engine code stamped on the back? I'm doubtful even with my camera phone and mirror.

http://www.marinemechanic.com/merc/d...lockcodes1.PDF
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Old 09-17-2015, 03:46 PM
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Originally Posted by donzi matt
The 420 had Gil exhaust and could either have a Weiand single plane intake or a GM dual plane. Pop the oil cap off and look at the rockers. A 420 should have Crane gold rockers, a mag will have stamped rockers. Nothing about that engine looks like a 420.
Back in the 80's we had a pair of one year old 365's and they had Crane Gold Rocker Arms. They could have been 370's......it's been a lot of years...but definate of one of he two hp's and definate had those rockers.

Edit in: relaxed my brain, lol, and remembered 100% they where 370's. Man, time is flyin.

Last edited by SB; 09-17-2015 at 04:30 PM.
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Old 09-17-2015, 03:46 PM
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Originally Posted by SB
Flame arrestor cover means nothing if engines been replaced or rebuilt.

Get some documentation !
Yes. This is my concern as well. From the picture above, do you think I'll likely be able to see the engine code stamped on the back? I'm doubtful even with my camera phone and mirror.

http://www.marinemechanic.com/merc/d...lockcodes1.PDF
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