Buy a used block will parts swap?????

karayj

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Aug 4, 2002
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468
1989 Merc 3.7 225 165 hp I have a 0C520320 the engine block I am buying is a C460580. The seller is keeping the intake manifold /exhaust manifold /starter/ heater exchange . I hope my parts will fit on the new block.
 

cyclops222

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Mar 21, 2024
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Hope is not going to make a successful swap.
Accurate examination by a experienced mechanic on both engines is needed at this time. Nothing less will do.
 

karayj

Chief Petty Officer
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Aug 4, 2002
Messages
468
I appreciate your input, but you need to understand. I used to work on cars and boats. I’m trying to get verification of something. I’m pretty sure Zach accurate already. When manufacturers make engines, they usually stay consistent for a few years this way when they make parts for that block, they can sell a variety of manifolds or different parts to many people

If you change the engine block every year, then you’re in for a nightmare because you’ll be making different parts every year

The other thing you need to understand is we’re here because we don’t wanna hire a mechanic. It doesn’t make sense to come here and then hire a mechanic unless you wanna make sure you’re not getting ripped off. We’re here to learn how to fix and take care of things ourselves.

Mechanics I purchased two boats that were maintained at a boat marina and when I got a hold of the boat, I couldn’t believe some of the stupid things that were done to that boat and surprise these mechanics actually had jobs

I also picked some brains of some mechanics on an issue. I was having where the boat would run for 20 minutes and then die and then 20 minutes later run again. They told me they said the carburetor they told me to check the fuel pump. It was the resistor wire, not doing its job by lowering the voltage to the coil, causing the coil to overheat and fail. I figured that on my own. Now there are two people on this form that pointed me in some direction of the coil.

What I’m saying is don’t always think that a mechanic is the end all all of knowing things sometimes you’ll find that people that went through things like this place will give you better advice.

I will say though thank you for reading my post and giving me a suggestion. I appreciate that.
 

Scott06

Admiral
Joined
Apr 20, 2014
Messages
6,451
I appreciate your input, but you need to understand. I used to work on cars and boats. I’m trying to get verification of something. I’m pretty sure Zach accurate already. When manufacturers make engines, they usually stay consistent for a few years this way when they make parts for that block, they can sell a variety of manifolds or different parts to many people

If you change the engine block every year, then you’re in for a nightmare because you’ll be making different parts every year

The other thing you need to understand is we’re here because we don’t wanna hire a mechanic. It doesn’t make sense to come here and then hire a mechanic unless you wanna make sure you’re not getting ripped off. We’re here to learn how to fix and take care of things ourselves.

Mechanics I purchased two boats that were maintained at a boat marina and when I got a hold of the boat, I couldn’t believe some of the stupid things that were done to that boat and surprise these mechanics actually had jobs

I also picked some brains of some mechanics on an issue. I was having where the boat would run for 20 minutes and then die and then 20 minutes later run again. They told me they said the carburetor they told me to check the fuel pump. It was the resistor wire, not doing its job by lowering the voltage to the coil, causing the coil to overheat and fail. I figured that on my own. Now there are two people on this form that pointed me in some direction of the coil.

What I’m saying is don’t always think that a mechanic is the end all all of knowing things sometimes you’ll find that people that went through things like this place will give you better advice.

I will say though thank you for reading my post and giving me a suggestion. I appreciate that.
When I did my swap I used the parts diagrams from my old engine to new lease a list of intake cooling hoses etc by part number from old engine to new (4.3 to 5.0 swap)

There are good diagrams at marine engine.com

And i think mercruiser parts . Com

Best bet for knowing what you are getting into is to do your homework via the parts book.
 

Scott Danforth

Grumpy Vintage Moderator still playing with boats
Staff member
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Jul 23, 2011
Messages
49,588
are you just getting a bare block, or a complete short block (with rotating assembly)? or a complete long-block with rotating assembly, head, and valve-train?

longblocks swap easy, shortblocks swap medium hard especially with the ford valve train. bare blocks require a machine shop.
 

nola mike

Vice Admiral
Joined
Apr 22, 2009
Messages
5,367
Offhand I can't think of anything that would keep you from swapping either a long or short block. Afaik all of the 470 changes involved the accessories. That said, you're going to have a hard time finding anybody that knows year to year changes on these engines in that kind of depth.
 

karayj

Chief Petty Officer
Joined
Aug 4, 2002
Messages
468
I have a 1989 Merc 3.7 225 165 hp I have a 0C520320 the engine block I am buying is a 0C460580. the guy bought a whole motor but did it for the parts only.. Intake with carb/exhaust/starter heater exchange is all he wants and I can have the rest. So I need to add my starter /my intake/ my exhaust manifold.
When I search for parts both serial come up as the same engine and parts list .... pictures show the bolt patterns are the same for the exhaust and intake to the block by eye.
https://www.marineengine.com/parts/mercury_marine_parts/sn/0C520320/437B100BS/908_90

 

karayj

Chief Petty Officer
Joined
Aug 4, 2002
Messages
468
Does any one know the years of the engine based on the serial number? I cannot seem to get good info. I have and 1989 and the serial seems to suggest its a 85-82 block .....makes no sense

I have a 0C520320 the engine block I am buying is a 0C460580. I would love to get the years that would help. It would be great to find out they are 2 years apart..
 

tank1949

Lieutenant Commander
Joined
Apr 4, 2013
Messages
1,894
1989 Merc 3.7 225 165 hp I have a 0C520320 the engine block I am buying is a C460580. The seller is keeping the intake manifold /exhaust manifold /starter/ heater exchange . I hope my parts will fit on the new block.
make sure salt water has never been inside block! That's an old motor.
 

Dubed

Petty Officer 1st Class
Joined
Sep 3, 2021
Messages
373
I have a 3.7. Had it rebuilt and after the rebuild i had a cylinder wall fail. I grabbed the 1st good block I could find (which was quite a bit older) and had the machine shop go through it and bore it out, etc. Swapped all the parts over no problem.
Best I could tell, there's no difference in the blocks through the years, just all the bolt-ons.
 

karayj

Chief Petty Officer
Joined
Aug 4, 2002
Messages
468
make sure salt water has never been inside block! That's an old motor.
The motor is super clean you can tell it was stored and maintained well.
My only concern is the old parts to new used block...
I am looking to see the difference in production years from my engine to the other one
 

karayj

Chief Petty Officer
Joined
Aug 4, 2002
Messages
468
I have a 3.7. Had it rebuilt and after the rebuild i had a cylinder wall fail. I grabbed the 1st good block I could find (which was quite a bit older) and had the machine shop go through it and bore it out, etc. Swapped all the parts over no problem.
Best I could tell, there's no difference in the blocks through the years, just all the bolt-ons.
THANK YOU !!! That is what i thought too the bolt on's are the same just different designs I can adjust to if needed.
 
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