i rebuilt both of the engines from my searay 35 footer.340 horse 454s.i installed mellings 10778 pumps and am useing 15w40 shell rotella oil.i ran both of them on the run stand ,they idled at 80 and after the oil warmed up they idled at 60.rod bearing clearance .0022,mains .0026 to .0029.0032 on rear main.after the oil warmed up a little i set the total timing at around 4000 rpm.oil pressure was at 75 lbs.these are 1990 mark4 engines that came from merc with the 8 qt aluminum pans.in a different deal i helped another oso brother sell a sbc that sat for a number of years,i hooked up my 120 lb oil gauge and it berried it while priming with the drill,i thought that was strange but did not pay much attention to it.i then put it on the run stand and started it,within 5 seconds i had to shut it off because it blew a ton of oil past the rear main seal and it berried the oil pressure gauge.i took it off the run stand,put it on an engine stand and removed the pan,pump&rear main cap.i tested the pump on my pump dyno and it berried the 200 lb gauge.long story short the oil that was laying in the bypass valve turned to gunky crap and caused the bypass to stick in the closed position,i took the bypass spool out,cleaned it and the bore it rides in reassembled&retested and it made 77 lbs pressure.i then replaced the rear main seal,cap and bearing,and oil pump then reinstalled the pan,refilled the oil[15w40 rotella and reinstalled the engine on the run stand and ran the engine.80 lbs cold and 70 hot at 4000 rpm.this experiment prooved to me the pressure potential of a gear pump and what can happen if the bypass valve gets stuck shut.this is my experiance and why i made my post.on another note i must be lucky because almost every engine i build gets a mellings 10778 pump and i have never had a dist gear or cam gear go bad.now that i said that the next one will no doubt take a chit.

I'm with you Mike. I put the 10778 in my one engine that I rebuilt because I wanted to make sure there was enough oil pressure at the turbos. I also liked that the 10778 gears are supported in the bottom cap. In a car the standard HV and HP oil pumps work fine, but my thinking is that in a boat with the high RPM's that if you want higher pressure wouldn't you want the gears to be supported on the top and bottom?