Changing gear oil in mechanical fuel pump in 525EFI...
 

Not sure how many experience this, but I find changing the gear oil in the fuel pump a pain in that you have to turn the whole thing up and down and sideways to clear the gear oil out. And then you're filling it from the side and have to wait for it to seep out to see if its full, etc. I had this thought that it would be great if it had a drain of some sort on the bottom, so I bought some 1/8" NPT plugs and was going to drill and tap a drain plug on the bottom that I could also use to fill from. And it's winter, so I need something to keep me busy...LOL... But then I sort of chickened out figuring it's a once / year task and I'll be kicking myself if I ruin a pump that costs a few hundred to replace.

Anyone ever do this?

I've read somewhere (maybe here) about doing this drain plug. Not sure how you would fill from the drain plug without making the same mess as filling from the fill plug. I agree - it's a mess with the current setup. I've yet to install drain plugs but think about it every time I change the oil in the reservoir.

Yes , except I put a small brass ball valve in ...... there's plenty of matl. on the bot.
Surprised how much fuel had got in them so changed the mech. pumps , bearings and seals , had to put a speedie sleeve on one shaft where the seal runs also.

Any chance you could post a picture? Would like to see where you drilled...

Me too. I remember reading it, but I couldn't find it. The plan for filling it would be to attach a hose barb/MPT fitting to the other side of the gear oil pump hose (the one that you attach to the oil bottle) and pump it in from the bottom and then turn it upside down, remove the fitting and replace with the plug.

I no longer run the fuel pump on mine so I don't have the diluting issues, But when I did, I drilled and tapped the bottom to fit a lower unit drain plug, 3/8x16 I think. Removed the plug to drain and filled it through the side with a syringe made for meat marinade. worked well

Be glad to , next Tues. I'll be checking in on it. If I remember right straight back from the fuel pump mount the floor of the cavity levels out , should have came that way from the factory.
The plan is to use the fill as a sight plug only , so need to see how it works.

Did you go with a electric pump ( like a a1000) with a return line to the tank ?

Mine was a 575SCI, but yes, I replaced it all with a Weldon pump with a return

The stock set-up is a P.I.A. for sure. Merc wants you to maintain the fluid but doesn't give any easy way of actually doing it. Poor design. I remember a few years ago there were pictures posted on OSO of a brass drain and using a turkey baster to refill while the assembly is still mounted on the engine un-disturbed.