1981 120 mercruiser broken rocker arm

[Dannysmyk]

Hello all,
Been hitting it hard this summer trying to get out as much as i can but ran into some trouble the other day. Was cruising at about 3800RPM when all of the sudden the engine started to backfire terribly. Came to a stop and started to poke around when i removed the vale cover i noticed a broken rocker arm. I purchased a new one and plan to put it in in the next few days but im wondering could this be a freak accident or just the failure from another more serious issue. Also what is the "protocol" and what should i look for to see if something else caused this to happen.
Thanks, Dan

 

[kenny nunez]

I have had brand new engines break a rocker arm. Never had a problem after replacing them.
Make sure the stud is not partially pulled out. Use a straight edge or just eyeball the one that had the problem. Check the compression to make sure that a valve did not float and from a bent valve.

 

[Scott Danforth]

You have a 45 year old motor

Anything could have happened. Could be rust, a nick in the arm, binding

They are cheap stamped rockers