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Is this a 454 7.4L?

Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=50165
Printed Date: November-22-2024 at 11:29pm


Topic: Is this a 454 7.4L?
Posted By: skyfuzz
Subject: Is this a 454 7.4L?
Date Posted: August-27-2021 at 7:20pm





I may have to replace this engine since it may have a cracked block and was told by the techs at the boat shop that if I need to repower my boat, the replacement block has to be the same size big block 7.4L. When I bought the bought 6 years ago I was told this was a Mercruiser 454. Not sure if it was a rebuild or just pulled out of one boat and put into mine. Or if it sat for a while or even how old it is. I do know for a fact that it was installed into this boat in 2015. I don't have the engine knowledge and expertise and, I'm trying to maintain trust in my long time boat shop. Hoping someone here has that skill to look at it and say that it is a 454 7.4L. This may help me with a rough idea of how much a replacement block is going to cost me. Thanks!  


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http://www.correctcraftfan.com/diaries/details.asp?ID=7613&sort=&pagenum=1


Replies:
Posted By: KENO
Date Posted: August-27-2021 at 7:44pm
It looks like an engine from a boat shop in New Hampshire that likes to paint everything........just everything Wink

I have no experience with the place, if that's where it came from.

I do see their, well painted Craigslist ads from time to time though.

It's a big block Chevy engine, most likely a 454 but you'd be better off verifying that with block casting numbers

Posted By: Jonny Quest
Date Posted: August-27-2021 at 9:11pm
There’s a spot on the Holley carb they missed…that’s a lot of paint.
Yup, BBC for sure.  As KENO says, you will need to verify with casting numbers to confirm more details than just Big Block Chevy. 

JQ


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Current
2003 Ski Nautique 206 Limited

Previous
2001 Ski Nautique Open Bow
1994 Ski Nautique Open Bow

Aqua skiing, ergo sum

Posted By: skyfuzz
Date Posted: August-27-2021 at 11:27pm
A well known boat restorer in a NH town that dealt with Chris Craft/Lyman etc crafts and engines sold me this engine when I hired him to do a full stringer/flooring job for this boat in 2015. He was in business for decades there but I believe has since then sold the business and moved out of state. Thank you for your valued input to my question. 


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http://www.correctcraftfan.com/diaries/details.asp?ID=7613&sort=&pagenum=1

Posted By: MrMcD
Date Posted: August-28-2021 at 1:58am
It certainly looks like a 454, which is also known as the 7.4L, two names = same engine.  The same size engine with identical outside size could be a 396, 402, 427 or 454, heck some were stroked to be a 496.  No way to tell from the outside what it actually is but as noted 454 is the most common.  If it is just cracked from a freeze you might be able to salvage nearly all the internal parts and use them for your new replacement engine.
I would pressure test the block before removing anything to see if your shop advice is good or bad.  Sometimes a freeze just pushes out a freeze plug and all you have to do is push a new one back in.


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Posted By: KENO
Date Posted: August-28-2021 at 7:31am
Not that it matters as far as the block goes, but the exhaust manifolds are either original Crusader BBC manifolds or some Barr Marine replacements. The raw water pump and thermostat housing look to be Crusader too.

The engine may be a Crusader not a Mercruiser under all that paint, but the block casting numbers will tell you what size your block is and how old it is

As a guess, it's pretty old, like 70's or 80's.

So far, I'd think you have no reason to distrust your shop, Wink


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