300x NEW POWERHEAD

[carguy]

My tech is about ready to put my 01 300x back toghere.
The number 5 piston blew. Just wondering if any one out there
has any ideas or tips as we put the new powerhead back on.

[jerry]

watch out how you tighten the powerhead studs, the 4 long studs , i think only get tighten to 25lbs , check it out call a good dealer

[300x Stoker]

They used 2 different gaskets for the powerhead. Depending on which gasket is used determines which torquing you use. On one you use all three stages of torquing. On the other you leave a couple of them at stage 2 torque. That is what the service manual says. Someone on here says that improper torquing is the reason the #5 rod was coming out. The manual warns of serious problems possible if the proper procedure is not followed.

Do they use an unbalanced torquing on other Merc motors?

Lots of motors seize up or melt things but the 300X has the rep for throwing rods that the other motors don't seem to have, if I've got the story straight.

Did you ever tell us what oil you were running and under what conditions you were operating when you had your unfortunate experience ??

[carguy]

I used mercury preium plus. I was runnng in some chop but only @ 6300 R.P.M. I think my problem came from the guy i bought the boat from he had the boat rack stored in savana and so i think the marine gas may have a lower octane.