Hello Everyone:
I still havn't resolved my problem with my boat engine. Let me bring all up todate.
Removed head, shop fixed 2 tuliped valves. Adjusted valves cold, several times. Didn't want the mess in my boat to adjust while running but not sure they are right.
Engine run good up until about 2500 rpm's, has no more after that. Checked all cylinders by pulling plugs wire off, while running , they all seem to be firing ok. You can hear a little popping out the exhaust.
What steps should I take to resolve?

Thanks to all for your help
leonard