525 fuel pumps
 

ok pulled both mechanical pumps and starboard motor that was running out of steam at 4700 had more fuel in the gear oil than port motor did. used hypo and sucked both out and replaced gear oil. Cant see a thing wrong with diaphragm. Reinstalled. Anybody have knowledge whether fuel pump is actually bad or do these things have "built in" leakage where hardware is crimped to diaphragms? Anybody decide to use block off plates and goe with electric pumps?

They always leak sir. You probably havent replaced the lube in awhile (if ever), and thats why it was full of fuel. Most guys change that lube every 2 years. I'd replace both...its good insurance (and piece of mind). :drink:

Great thing about twins is you have a complete set of "spare" parts to swap from one engine to the other and see if the symptoms follow.
Did you swap those mechanical pumps when you had them off to see if the symptoms follow ?

525 fuel pumps
 

didn't think to swap pumps. Have a new one on order so at $110 I'll see if that fixes that side. One pump isthe newer style with angled venttube and other is old style with straight tube. Problem motor has newer pump. I asked previous owner about pump history and he said couple yrs ago replaced one. I was thinking that there was so much fuel oil thatthere was not much room for diaphragm to pump at full stroke and that might be cause for low pressure. Holy Cow recognize ur boat from Buff Poker run. Great time...my first run...won't be my last (37 AT "Thunder")
Plan to hook up to water seperator mounting block with 0-15 psi gage and watch to see if dash pressure gage ( high pressure from electric pump) follows low pressure (mechanical pump). I figure if low pressure stays in spec and high pressure falls off I'm narrowing it down.