Mercruiser 496 MAG Refresh Thread

AShipShow

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No, one almost in the center and one out near the perimeter but in one.. the one near the center will be a real PITA if I try to fix it.. not much access to wire brush it or even get a dremel or anything in there
 

AShipShow

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Well I tried my hand at silver soldering the easiest one I could get to with really no luck... Not sure if I didn't get it clean enough or whats going on but I couldn't for the life of me get the solder to wet out to the tube.. It should have been clean enough. Most likely wasn't able to get enough heat into it..

I wasn't holding my breath that I was going to be able to fix it, so I'll wait on some responses from a couple local industrial radiator repair shops and see what they say, but at this point, I'm leaning towards replacement with a Seakamp or Mr. Cool unit.

On that note.. I'm seeing that there are both 3.5" and 4" heat exhangers for the 496 but the mercruiser parts diagram shows the same 4" model on all the serial numbers I've checked so I'm not sure whats going on there... Mine matches the dimensions of the 3.5" unit, so I'm wondering if they were supersceded or something and all are now replaced with the 4"... Anyone have any insight on this, or if I can use the 4"??? It seems like it would fit.

EDIT: Nevermind... did a little more digging and confirmed that the 3.5" unit is no longer available and is superceded by the 4" heat exchanger... which for whatever reason is 100 dollars cheaper at mr cool lol... I'll call that a minor win
 
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alldodge

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Looking at Mercruiser parts dot com, all show 363903A01 and don't see any revisions
 

AShipShow

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Looking at Mercruiser parts dot com, all show 363903A01 and don't see any revisions
Yea, thats what was confusing, it didn't matter the serial number, it just showed the new PN.. Usually it will say the original PN and then what supersedes it.. Anywho.. this is the original 3.5" version and you can see its replaced by the 4"..
Screenshot 2024-12-09 081530.png
 

alldodge

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Must be your serial number, I'm just looking up by picking a few and they don't show that
496.jpg
 

AShipShow

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Welp, got a no-go from 2 of the 3 radiator shops, so assuming the 3rd is going to be the same, I decided to just pull the trigger on a replacement.. Ended up calling Lenco and spoke with the owner... I've read good things about them and coincidentally was the best price I've seen so far.. I guess these things are built to order.. He said he'd "slap it together this week" lol.
 

Scott Danforth

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these heat exchangers are nothing more than plumbing tubing and fittings with a few castings tossed in.
 

AShipShow

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Oops, haven't been here since early December...

I ended up receiving the new heat exhanger from Lenco and it looks like really good quality.. It was a lot heavier than the OEM heat exhanger.. not sure if thats any indicator of quality though.
Ended up getting it installed with a few minor hiccups (mostly me being dumb)... I did a pressure test once it was installed and found a leak.. Ended up being the hose from the coolant reservoir to the crossover tube.. Ordered and fixed that and happy to report no more cooling system leaks.

After that was sorted out, I ended up pulling my injectors and sending them off to get cleaned since I have a cool fuel 3 module. The module surprisingly seemed to still have paint inside so I don't think they are clogged, but being as old as they are, and the boat having sat for 3 years, figured it was a good idea. Still waiting to get them back, hopefully they all test good.

I think once I get the injectors back in and reinstall the wiring harness, I will be ready to fire it up on the stand and test it out.
I think I know the answer to this, but can these motors be run out of the boat the same as all the old (dumb) carbed motors? I had done it with my 5.7L by just jumping the 3 pins in the engine harness.. I'm just wondering if with all this other wiring, there are other components that need to be hooked up to the motor and if not, the PCM will be cranky and not let the engine run if it doesn't "see" something?
I'm assuming it won't be an issue, but curious if anyone knows for certain?

It would suck to have to reinstall it in the boat just to find out there are issues and then have to pull it again.
 

alldodge

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If the motor has the round 10 pin plug then yes it can be run on the stand the same way
 
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