3.0L Merc, parts interchangeability

Baylinerchuck

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Is there a definitive list of changes over the years for the ole Iron Duke? Something that lists this head has these port sizes will only work with this manifold, etc. I think for the most part the 3.0 blocks are interchangeable with exception of the ring gear being different pre 90 vs post. It would be interesting to see the changes over the years and what works with what.

The reason for my curiosity:
Buddy of mine bought a 2003 Chap and found out through the S/N on the block that it’s from the late 80’s. Head is gray like it’s OMC, manifold appears to be 80’s as it has the bolted on endcaps with water jacket in one endcap. I think it’s going to be difficult to change over to a 2000 long block. Probably better to find a donor boat at this point. Who knows what was changed to put this late 80’s motor in.
 

Bondo

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Is there a definitive list of changes over the years for the ole Iron Duke?

Donno,...... The Iron Duke was never used in a boat,..... a Pontiac based motor,......

Ours are Chevy based motors,.......

While maybe not Ideal,... a 2000 long block could be dressed with the parts ya got, except for the flywheel,......
 

Baylinerchuck

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Donno,...... The Iron Duke was never used in a boat,..... a Pontiac based motor,......

Ours are Chevy based motors,.......

While maybe not Ideal,... a 2000 long block could be dressed with the parts ya got, except for the flywheel,......

Thanks for the reply, it been awhile since we chatted.

My apologies, your comment made me go back and look at the history of the 2.5L. I assumed wrongly that the 3.0 was a derivative of the 2.5L called the Iron Duke. As you point out this is a Pontiac motor, not the GM. The Pontiac iron duke being 151cu while the Chevy was 153cu. :help:

I get confused with Pontiac vs Chevy, beings I remember both wearing the GM brand and don’t really remember them being separate entities. I tend to follow the Ford history a tad bit more closely. I’m sure Chevy guys won’t hold that against me......

So are their any resources that list compatibility, or is that just pissing in the wind? I did a brief search online and didn’t really come across anything.
 

Scott Danforth

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And yes, the iron duke was half a pontiac 301, while the 2.5 or 153 was a 230 6 banger with 2 cylinders removed. The 3.0 shares the mount locations of the 2.5 (153), however shares very little with it.. Today, the 3.0 is pistons from a 5.u and a slightly longer rod

only the valve cover bolts are similar between the 151 poncho and the 153 chebby
 

Baylinerchuck

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Thanks for the follow up Scott. Much appreciated. Definitely saw the 90 and older thing. Seems there was also some changes mid 90’s.
 
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