"Define "direct drive"
"Define "direct drive". Surely you've got a transmission in there somewhere??
IF the engine is running correctly (secondaries, timing, compression, good ignition etc) then your max indicated rpm is primarily a function of the prop.
The carbureted 351 in my boat is supposed to turn between 4000-4400 RPM at WOT. I have had my prop tuned to slow it down just a bit and my max is just over 4000.
Many newer engines seem to spin a bit faster...up to 4800-5000. Check with the manufacturer of your engine to determine."
