Quote Originally Posted by Mark75H View Post
No problem that I have seen with running the 44's at 7,000+


In fact, they usually run 8,400. I have not seen a bearing failure
I guess I should have qualified as to what "old mercs" we are taking about here. If old means 30 years old, engines from the 70's and 80's then we are talking about these engines. If old means the earlier Mark 55h and the 44 cu in 500's of the 60's, that's a different story. The Merc 44's from the 70's and 80's had tighter rod clearances than the earlier motors and if you spin them too fast you will damage the rod bearings and the crankpin journals. The change was made to make the engine more quiet, but the result is that you can't spin the later classic engines as fast without opening up the rod clearances. This includes the 44xs and any of the "classic 50" powerheads from the 70's and 80's.