Help with piston ring PN application

[Moody Blue]

Looking at buying a set of rings (39-50587A 12) for a 1971 Merc 800. I have two of these motors torn apart and will be rebuilding to make one out of the two. Both motors have 3 rings per piston. All the parts sites I checked show only 2 rings per piston. The PN above is apparently for the 800 GS and 800 DR models, whatever that means. I have searched and can not find any listings at all for the above P/N.

Does anyone know of a site where I can do a "where used" search by PN for the Merc motors?

 

[Laddies]

Re: Help with piston ring PN application

Item # 24. http://www.mercruiserparts.com/Show...0&bdesc=CRANKSHAFT,+PISTON+AND+CONNECTING+ROD

 

[Moody Blue]

Re: Help with piston ring PN application

Thanks Laddies, but that page shows only 2 rings per. The pistons I took out of the two motors I have, each have 3 rings per.

Would also like to find what year the pn 39-50587A 12 applies to and if they would be compatible with my motor.

Where else to look?

 

[Chris1956]

Re: Help with piston ring PN application

Merc changed from 3 ring pistons to two ring (Keystone type) pistons, after you motor was made. You should be able to use either piston, in any cylinder. See if you can get a PN for the rings from a dealer. You also might try Sierra

 

[Laddies]

Re: Help with piston ring PN application

I don't know were you came up with the number you have but both Mercury Marine and Sierra parts books say that your engine uses the same rings Mercury #39-78816A12 or Sierra #18-3902. The part numbers are for 3 ring pistons with a bore of 2.875 and in the serial range of your engine. The Mercury rings are packed in 12 per box and the Sierra are 3 to the box, we use both types regularly.

 

[Moody Blue]

Re: Help with piston ring PN application

OK guess I'll stick with the known entity. The p/n I had was supposedly for a Merc 800 but year unknown.

Was a good deal but no good I guess if they won't fit.

Thanks for the help.