150 black max won't run a full throttle?

Question

It will accelerate fine to full throttle but then dies to an idle. After a few seconds I can accelerate again. Does this sound like I'm sucking air somewhere in the fuel line?

Answer 1

Check for water in the fuel sysytem.  look for air bubbles in the screen bowl,  Really you need to do a fuel output test from the pump,  sure sounds like reduced fuel flow, or water or debris plugging the hispeed ports.

Answer 2

does it die, or drop to idle?   With the throttle still at WFO?  if you leave the hammer down, does it recover and accelerate on it's own, or does it quit running?  What happens if you punch the choke when it dies back?

just to be clear, what year is that?  carbed inline six, right?  six carbs?  Choke plates or primer system?

Have a feeling If it was sucking that much air, you'd never be able to prime the line, or at least, it wouldn't hold pressure.  But if you want to check on the fuel pump, shut 'er down when she dies back, and drain the carbs...if they're full, it's not the pump.  

Squeeze the primer bulb when it dies back - if it collapses (refuses to fill back up), look for debris in the tank or blocked vent.  If you've got an anti-siphon valve, get rid of it, outboards don't need it anyway but some boat makers put 'em on there.

Inspect the wiring coming off the stator & trigger, look for chafed/burned/missing insulation, wires that might be touching when you throttle up.

Inspect the ignition coils for signs of cracking, or dripping epoxy.

Then I'd do a compression test, and spark test, if those check out, at least you know you're dealing with fuel delivery.