Force 150 head bolt torque spec ?

[HotTommy]

I'm buttoning up my 1993 Force 150 outboard after replacing one piston. I just installed the head and a new head gasket. My factory service manual says the bolts should be tightened in the order specified to 75 in-lb, then 125 in-lb, then 175 in-lb, and finally 225 in-lb. My torque wrench and I are used to working in ft-lbs, so I converted the specs and discovered the maximum torque level is barely 19 ft-lbs. That's little more than finger tight in my world. I don't doubt the FSM, but I'd feel reassured if some of you with much more experience than me told me this is indeed correct. That barely seems enough bolt stretch / clamping force to keep them from vibrating loose. There was also no mention of either anti-seize or Loctite.

 

[Frank Acampora]

Re: Force 150 head bolt torque spec ?

The bolts are 5/16 diameter (1/2 inch heads) and the numbers you quoted are correct. In fact, I believe that the specified torque is a bit higher than standard torque for a bolt that size but the head bolts are (should be) grade 8.

19 foot pounds does not seem a lot, but remember that you are going into aluminum. Also remember that due to the helix angle on the threads, the clamping force is MUCH greater than the torque value. 225 inch pounds is fine and you will not get any head gasket blow-out.

Personally, I prefer to torque to 225 inch pounds because it is more accurate: If I slip a little, I have not greatly exceeded the spec. You can buy a cheap but adequate inch pound torque wrench at Harbor freight.

 

[jerryjerry05]

Re: Force 150 head bolt torque spec ?

I go with my ft.pounds wrench.
I use 20#
15# then 17# then 20#
I use triple guard grease on the threads.
It will help it to come loose if there is a problem later.
Some will re-tourqe after a 10hr breakin.