Roomers and the Merc 15

[G Stillwill]

There are some roomers going around about the Merc 15 in A ,AXS and J class and a gray area around the rules in the inspection manual. The first is which has been addressed is plugging the pee hole in the adaptor plate for the tuned pipe which there is a measurement for. Easy to check by the inspector, just pull the prop and start the motor with just the gear foot in the water if no water comes out the exhaust snout then its plugged. The next is that some are plugging the idle relief holes in the block which there are also measurements for, these are the two small holes just above the exhaust ports. Again easy to check just pull the exhaust plate and see if they are plugged. I don’t know where the gray area is other then it doesn’t come right out and say its illegal to plug the holes.

Hole sizes
Pee hole 0.120 +/- 0.0010
Exhaust relief holes (2) : one has max dia of 0.120 and one has a max dia of 0.350

[Tomtall]

Merc 15

Heck G. they might as well let them do that stuff too. They already approved that any bearing can be used in the 15 merc. Wonder how many are running Ceramic bearings now? Thats OK, us faithfull OMC owners will keep pluging along with whats original from the factory.

[John Schubert]

Heck G. they might as well let them do that stuff too. They already approved that any bearing can be used in the 15 merc. Wonder how many are running Ceramic bearings now? Thats OK, us faithfull OMC owners will keep pluging along with whats original from the factory.

Yes but!, they eventually allowed plugging the OMC A's as there was such a descrepancy on residue "flashing" that they allowed it to be plugged. :

[Tomtall]

Yes but

Yes but!, they eventually allowed plugging the OMC A's as there was such a descrepancy on residue "flashing" that they allowed it to be plugged. :

The merc. 15 is also 2 cu. in. bigger than the OMC 13.2 cu. in. motor. I guess things are kinda close now. Oh wait, the 15 merc. in AXS class dosn't have to run a restrictor plate.

[werners racing]

15 merc

why not get our young racers mixed up right from the get go hey dad now you no why the mercs kick our ass in j

[les]

Max Min dimension

"Exhaust relief holes (2) : one has max dia of 0.120 and one has a max dia of 0.350"

If no min dia is specified, then I would think they could be 0 dia.
Mabey not the intent, but what is the min diameter? .115 ? .110 ? .001 ?

[Mark.Wheeler]

George,

It is illegal to plug each of the holes you mention.

Mark Wheeler, Co-Chair
APBA J committee

[G Stillwill]

Mark I figured it was, none of the ones that I built were pluged when they left here nor are any of mine pluged, just wanted to bring the roomers out in the open.

[crankbearing]

idle holes.

Those holes are actually decompression holes after a long discussion with the engineer that designed that motor the first blocks on the 15 did not have them to begin with. Mark you can talk with Aaron about this.

Regards,

[G Stillwill]

Dave I have two blocks that dont have them but both are pre 1995 blocks which also have different ports then the ones that were made from 1995 on.

[crankbearing]

newer as well

Hey George,

I would hate to be an inspector for that motor. there have been almost 10 revisions on that motor since 98. The piston have been revised 8 or 9 times if I recall and the block as well.. the motors from the factory are 12 HP the one he has that has been tweaked is 22 on the dyno. He does not race it. New sleeves do not have the holes in them.

Regards,