J / AX Block and year iD Info

[dwwmotorsports]

Looking for a education on identifying legal and non legal components for Mercury running in J and AX . Thanks Dave

[Fastjack]

1999 and newer - O ring port covers -" rubber " reed block - flat switch box - no hump - cranks - pistons - rods seem to be all the same . George Stilwill put out a list several years ago on HR perhaps you can find it ..

[Team B&H]

The above is close but not totally accurate. A 99 or later 15 will have all legal parts. So do 99-up 9.9 motors save for carb & exhaust plate/pipe. Proper blocks go back farther (95 I think) which have bigger transfer passages, ports and the o-ring port covers. Keep the reed block with the correct block. 99 and newer have the only legal ignition/flywheel parts although I think older triggers may work but flywheel, switch box and stator are different pre-99. Old ignitions use a 1 magnet flywheel (lighter) with a two-coil stator and a switch box that switches coils as rpm increases. New and legal ignition has 2 magnet flywheel (heavier) and the switch box figures which one to use at which rpm. One stator is red, one black but offhand I don't remember which. And no, the correct switch box/stator doesn't run on 2 cyl with the light flywheel. My guess is that the difference was for cost reasons as one more flywheel magnet must be cheaper than winding and assembling the 2 coil stator. 15 hp crank, rods, pistons go back very far but 9.9 or 6/8 may be smaller bore and have different center main bearing setup. 15 hp carbs are pretty generic. Use a short shaft motor for driveshaft housing but otherwise powerhead parts are same short vs long. The small motors donate the basic carb restrictor plate for J if you want to eek out the absolute max width.

[dwwmotorsports]

Thanks for the helpful information, can someone point me to where I can find the correct part or casting numbers on these parts? I am not sure that I'm looking in the right place? I have a block now that has a 875-8474-02 number on it but can't seem to ID it ? Dealer said no such number in the catalog I think its a mid 90's 9.9 but not sure of anything else. Also not sure what to look for on the port shapes, If someone could post a picture of the two different shape that would be great. Is there a block combination that is better than another or is it the luck of the draw? same with other parts year, casting batch run?

[Team B&H]

If it has a transfer cover with an o-ring instead of a paper gasket it should be legal. None with a gasketed transfer cover is legal. The external cover shape is different so if you know the difference you don't even have to take the cover off to see which it is. I never kept track of part or casting numbers.

[dwwmotorsports]

Please tell me what you are calling the transfer cover?

[Team B&H]

The transfer cover covers the intake ports. Its a 3 bolt cover on the intake (opposite side of exhaust & ignition parts) side of the block (starboard)

[Team B&H]

Stumbled onto my notebook. 97 and up motors have the rubber coated reed block