Hey Folks,
I have a Mariner 8M, Serial Number 677S 035288 (Yes, that is an "S", not a "5") From what I can figure out, the year built is 1980.
Had to pull the head for a water passage problem. Tried to put it back together and started snapping off head bolts. I've got a manual for 1990 or newer mariner that says the head torque is 60 FT LBS. Based on the breaking of the bolts and the size, this can't be right.
I am going to tap the head holes to the next size (1/4") and need the correct factory torque specs for the head bolts.
Eric, that must be a misprint, more likely 60 Inch-Lb is correct for that size of bolt.
Note, when in doubt, you can consult generic S.A.E. fastener torque charts (just Google it up) to see if the torque value given seems to at least be within reason.
Approx 70-80 Inch-Lb would probably work for 1/4" fasteners.......ed
p.s. multiply Ft-Lb by 12 to get the equivalent in In-Lb!
Actually, my initial torque was 120 inch/LBS (10 Foot/LBS)
that is right were the bolts started to strip and/or break off.
I wish I had access to an original manual from that year and could check the torque.
At 120 Inch/LBS, the gasket wasn't really seated competely based on visual inspection after removal.
My guess is that the torque should be greater than 120 Inch/LBS and lower than (60 Foot/LBS). I think that corrosion has weakened the threads on some of the holes, hence the stripping.
If anyone has a manual from that year, can you please report on the factor head torque spec?
Thanks in advance,
Eric
Ps This is an outboard made by Yamaha for Mariner...
Found two manuals that quote 60 Foot LBS and 60 Inch LBS as the torque spec. I ended up torquing all bolts to 100 Inch Pounds. Engine is running well, but I have some head bolts that are tapped to 1/4" and 5/8" because of the previously bad spec (over-torqued and stripped/broke). The remaining original bolts are metric, but are around
10-28 in American specs. That makes 3 different bolts sizes ! For 27 year old outboard that still runs well, I am very happy !
Need Head Torque specs for older 8HP Mariner
Linear Mode
