50 HP Head Bolt Torque

[mjohnston7]

I'm about to re-torque the head bolts on my 2006 50 HP Yamaha Outboard as it was suggested to me to have that done after the first 10 hours of use. The Head cover displays 29.4 Nm (M8) and 7.8 Nm (M6) for the torque values but I'm trying to confirm which bolts use which value. The Head cover has 14 bolts (12 mm socket) along the perimeter of the Head cover and 4 smaller bolts (10 mm socket) down the middle. All bolts have the number 8 stamped on them. I believe they would all be torqued to 29.4 Nm but wanted some confirmation before doing so on those smaller bolts.

 

[mjohnston7]

Re: 50 HP Head Bolt Torque

Purchased a SELOC manual and in the section on installing the head cover, it states that "All bolts should be torqued to 11 Nm and then 28 Nm". It doesn't differentiate between the different sized bolts so I'll assume that both the 14 bolts on the perimeter and the 4 in the middle are all torqued to 29.4 Nm as displayed on the head cover. I'm still confused as to what the 7.8 Nm (M6) that is also displayed on the head cover is in reference to. If anyone out there might know what, please pass that on. There are bolts on the engine that have the number 6 stamped on them so my guess is those bolts unless stated otherwise should be torqued to that specification.

 

[DMSOUTH]

Re: 50 HP Head Bolt Torque

The "M" stamping is usually the size of the bolt--M6 is 6 mm, M8 is 8mm. the M8 would take a 12mm socket and the M6 would take a 10mm socket.

 

[rodbolt]

Re: 50 HP Head Bolt Torque

NO NO NO STOP.
the M6 bolts,10mm CANNOT be torqued to the same spec as the 8mm head bolts.
they will break long before you hit the final torque
the M6 bolts are just water jacket cover bolts and have nothing to do with a cylinder head.
next time buy a real manual as about all clymer and seloc is good for is outhouse use.

 

[mjohnston7]

Re: 50 HP Head Bolt Torque

Haven't torqued anything yet so I got this information just in time. So one more question then. What does the 8 stamped on the bolt mean? Both the M8 and the M6 bolts have a 8 stamped on the head. There are some bolts with a 6 stamped on them. For example the bolts securing the oil tank to the motor are stamped with a 6.

Guess I will look for a "real" manual when the time comes for a water pump change.

 

[rodbolt]

Re: 50 HP Head Bolt Torque

the 6 and 8 markings are a bolt grade.
the 10mm hex is standard for a 6mm bolt the 12mm hex is standard for an 8mm bolt. dont confuse grade markings for bolt diameter.
glad ya didnt try it already. a poster did that here not long ago and I didnt catch him in time.