FWC Merc 165 riser gasket?

[savery]

I have a Merc 165 with aftermarket fresh water cooling; this includes the exhaust manifold, which means the manifold water jacket does not communicate with the riser. The original installation had a grafoil type gasket that covered the holes in the water jacket, and there was no block off plate.

In preparation to change the exhaust tube, I looked around and couldn't find exactly what I needed but through some deduction I ordered Barr marine MC-20-87918 stainless block off plate and MC47-27-41811 gaskets. However, as I found out once I received them, they are not the correct parts and the bolt holes do not line up. (I really wish manufacturers provided dimensions on stuff like this.)
Below are the dimensions I need (as well as I could do with a crusty old piece of cast iron), as well as some photos. Any ideas for a PN on a solid gasket and blank off plate, or is this a DIY job?



This is the original gasket.

 

[achris]

You've raised a good point. I have looked through all my parts manuals and can't see the closed cooling elbow gasket listed anywhere. I'll keep looking see if I find anything..

The 'normal' elbow gasket for the 165 is the same as the one for the log style manifolds on the GM V8s, so I've also chased that path down...

Chris.....

 

[achris]

Found it...

The block-off plate you're looking for is part number -55730. They use the standard gasket either side (27-52076).

Chris....

 

[achris]

Barr Marine MC-20-55730 Stainless Steel Block Off Plate

Barr Marine MC-20-55730 Stainless Steel Block Off Plate

marineengineparts.com

Complete with dimensions!

 

[achris]

Forgot to ask. This '165', 4 cylinder or 6? (I assumed 6)

 

[savery]

Heeey... that's it! To clarify, it is a six (250 CID) and that appears to be the correct part, although my dimensions are off by 1/16 (LOL)
Thank you!!!

I was beginning to think that this was either a "custom" job or had parts provided by San Juan Engineering (the HX manufacturer) and I was going to have to DIY a replacement. I'm pretty sure the riser was a "field modification" to add winterization drains since I haven't been able to find any like it. Mine is in OK shape and being principally used in fresh water should hopefully last for a while.