About half way down is picture of main system well air bleed holes. http://www.slantsix.org/forum/viewtopic ... 0&start=30

So if fuel starvation at 50% or 70% throttle is your suspicion, be sure to use USCG approved fuel filter and parts when you replace them.

Also, I seem to remember a stainless steel check ball on top of boat gas tanks. These have a tendency to collect crap from the tank in them and reduce fuel flow.

Please let us know what you find. Inquiring old minds with marginal memories want to go "oh yah, I remember that".