90HP Inline 6 (tower of power) carb rebuild - what size jet?

[Imjus4u2nv]

I am looking to rebuild my carb's on my 1985/1986 Mercury 90HP inline 6.

1) Serial number OA968445 which has always confused me as part list don't usually have letters in front of them (assuming I would fall in the last category below ("8071020 and up)? [h=2]90 (6 CYL.) - 5299506 THRU 5594656
90 (6 CYL.) - 5309951 THRU 5721324
90 (6 CYL.) - 5594657 THRU 6436122
90 (6 CYL.) - 5721325 THRU 6436122
90 (6 CYL.) - 6436123 & Up
90 (6 CYL.) - 7147088 THRU 7208847
90 (6 CYL.) - 7190903 THRU 7208847
90 (6 CYL.) - 7208848 & Up
90 (6 CYL.) - 8060545 THRU 8060694
90 (6 CYL.) - 8071020 AND UP[/h] According to the parts list, my carb should be either of these (I will know for sure when i get the boat out of storage in a few weeks):
WMK-30
WMK-35, or
WMK-39.

2) Parts list I am looking at shows a main nozzle (no part number), and then:
-Jet, Main fuel (.074)
-Jet, Main Fuel (.072)
-Jet, Main Fuel (.070).

How do I know which one to use? Do I use the same jet in all three carbs? Is there a benefit to going bigger?

Any help is greatly appreciated!

 

[hardwater fisherman]

It may be marked on the jets themselves.

 

[Scaaty]

Carbs will be marked what WMK. And the jets are marked. I run on my built frankenmerc 135 .0785 jets as thats the sweet spot. Also depends altitude where boating. Lower jets at altitude (less air, means less gas for proper combustion). Just stick new jets in (if even needed) same size. All carbs the same too...

 

[Imjus4u2nv]

Terrific, thanks so much. Will try to post the carb number and jet sizes once I dig into them! Love this site!

 

[jimmbo]

From an 1985 Merc Service Manual