71 Merc 800 reed blocks

In the process of rebuilding this motor (thread here http://forums.iboats.com/mercury-mariner-outboards/1971-merc-800-rebuild-refurbish-589826.html) and have acquired a couple replacement reed blocks (thanks to the kindness of a fellow iboater) but they are slightly different than the originals. Want to be sure they are compatible.

On the mating surface of the "new" reed block halves there is a small machined groove leading from the labrynth seal to the outer diameter of the reed block. The original reed blocks did not have this groove. OK to use in place of the originals?

Re: 71 Merc 800 reed blocks

Got everyone stumped I guess ?

Re: 71 Merc 800 reed blocks

All 99-c.i. reed blocks will interchange, as they are physically the same dimensions. Merc did make revisions like this groove, and on late-80's motors they had a funky 8/10-petal setup. All of the older-style reeds were 10-petals per side.

I would imagine that Merc added the groove to get more lubricating fuel/oil mix into the labrynth seal, this should reduce wear.

That being said, the next question is which way do you point the groove, since it is slanted! My best guess to that would be that the external part of the groove should point to the top, since oil will drain down to the bottom.

One caveat, if the reed blocks already have reeds/stops installed, make sure the stops are correct for your motor. Too big or too small will affect operation, there are specs for every model.

BTW I found an eBay auction with a good picture of that pesky groove: Used Mercury Mariner 115 Reed Block 8663A 3 8663A3 | eBay

HTH.............ed

Re: 71 Merc 800 reed blocks

Thanks for the info Ed. Good observation regarding the orientation of the groove. The word UP is cast into the block but I hadn't paid much attention to it yet. I have verified the reed stop heights but was not aware that there were different heights for different motors. Always good info on these forums.