I have 2 gear sets for sale.
1 New 1.25 upper 20/25 gear tooth count. $1800.00
1 Take out 1.33 upper 15/20 gear tooth count $900.00
These will only fit a #4.

will they fit a #3 mike 708 3089584

Mike, they will not work in your #3. The internal spline in the driven upper gear, has been "replaced" with what Mercury called a polygon. All #3 and #4 upper gears are the same except that #3's are internally splined and #4's are polygoned.

Gary

Gary, Thanks for answering that question. I did not see it until now; and thank you again; for your help and educating me about the gear sets as our conversations.

Mark

any educational pics available ? thanks in advance. J

Actually, you need to call Gary, for the gear set, if you need them.
After we sell what we have here, my client will purchasing the other matching set we need. This gear issue was dicussed in the drive section about #4 speedmaster gear ratios, if you would like to be informed.