The good news... It looks like I don't have the old syle "bad" riser gasket...

Port side

http://img.photobucket.com/albums/v5...27/photo37.jpg

Starboard side

http://img.photobucket.com/albums/v5...27/photo37.jpg


The bad news...

I redid my compression tests on cylinder 4. One cold and one cold/wet. The plain old cold test blew 92. After that, I added about 1 tbsp of oil, let it sit for a few minutes so the oil could work it's way into the rings and ran the test again. 106. Looks like my compression problem isn't in the top end after all. :-( That being said, it was encouraging to see the cold compression at 92 instead of 42 like the first time...

Prior to buying the boat, the seller did tell me that he sucked up some seaweed and I believe overheated the motor. His insurance paid for a bunch of stuff to be replaced, but he didn't recall what. I didn't know how sensitive this 470 was to overheating at the time, so I didn't think much of it. I am going to try and talk to him tonight to get some more information about what was done.

Sigh...

you got valve seat issues, go ahead and pull the head. Look real good at the riser to make sure its not burnt out and leaking water back into the manifold

Thanks.

For the distributor shims, would these be correct?

http://www.summitracing.com/parts/MOR-26140/


I've also found three different part numbers for the riser gasket on Merc's parts express. 18272 and 97542, which is superceded by 856705. Do you know which one is correct?

I am assuming it's 18272 as it has only has one scalloped side.

18272
http://www.mercurypartsexpress.com/u...mage_id=875675

97542/856705
http://www.mercurypartsexpress.com/u...mage_id=876774


Thanks for helping me figure this stuff out!