Mercruiser 5.7L 260 - what's the real or entire serial number?

[Blueghost924]

Hi, I can't quite read all the letters/numbers off my Mercruiser 5.7L / 260 Alpha One. I have a 1987 Regal Ambassador 255XL, but since we (boat owners) tend to swap out motors, I can't attest to this being a 1987 5.7L as well. I know the attached pic of what I can see of the serial plate isn't the best, but any ideas as to what the entire serial number should be?

 

[alldodge]

Seeing 202234, being a 350, I would guess a 82 to 86 series and the first two would be 0B so 0B202234

 

[achris]

That's not a Merc serial number plate. I also tried all combinations of prefixes with '202234', '202231' and '202284' and none are an inboard/stern drive engine.
I suspect that plate is a rebuilders' plate, and pertains to an 'in-house' serial number system.
Can you take a picture of the front of the engine (stand back a bit) and we could get you a rough year...

Chris..........

 

[Blueghost924]

Gotcha. Here's a couple more pics that hopefully will shed some more light on the engine...

 

[achris]

Hi mount steering pump and 4" elbows, first generation TB-IV ignition amp module and 'Alpha One' drive put it at 1986...

 

[flipbro]

How many bolts holding the intake down? From the one pic it looks like mabe a vortec style intake. Looking at angle of front bolt.

 

[Blueghost924]

Ah thanks Chris. I've seen a couple of diagrams on the Mercruiser parts website in which the schematics are a match. Good to know.

Flip - not quite sure about the intake manifold. Looks like there's 2 bolts in the front and 2 bolts in the back. I don't know if it's a Vortec, but it has to go. A local marine mechanic said that it's an aluminum intake - and that it's coating my valves from wear particles (interaction with seawater) and causing problems with compression. I need to replace it with a cast iron one...soon!

 

[achris]

Aluminium manifold + marine engine = not a good ending... Even in a freshwater environment an ali manifold is not really a good option. The engine is still pulling in a lot of 'wet' air...

The easiest way to differentiate a vortec from a non-vortec is the angle of the manifold bolts. Vortec manifold bolts are vertical, non-vortec are cant at an angle.

Chris.....