Ok, I think I have the courage up to change the oil in my mechanical fuel pump. 25 hrs on the oil since last change by dealer. Seems straight forward per the manual under owner maintenance. I have a syringe with a tube attached to it to fish through the fill screw opening and will have a bowl or something to catch the oil. Will use this set up to both extract and then replace with new HP Gear Lube. I will be vigilant of injecting lots of air into the bowl.

Any other pointers or advice????

Thanks in advance.

Have something underneath, most likely you will remove that fill screw and fuel laden oil with rush out.

The rest appears you know, suck out the old stuff and fill until it starts coming out the screw hole and reinstall screw.

You can remove completely and drill and tap a lower hole for a drain also.

yes, will for sure have a catch in place for the oil. Yep, have seen where others have drilled and tapped a lower hole for ease. Makes sense, but wont be doing so on this change. appreciate it!

Is there pressure behind that fill screw?

No, but when the fuel mixes with the gear oil it thins out and once you remove the screw it will run out because it will be overfilled. Again, assuming that there is fuel in it.

I added drain plugs so I do it every fall and life is a lot easier draining out the bottom and refilling through the side. At the cost and headache associated with burning up a pump assembly I sleep easier now

I've tried using a syringe with a 1/4" tube and sucking the lube out. You can only get about half of the lube out that way. The tube gets hung up.

Currently, I just turn the pump upside down and sideways until it all drips out but I've been wanting to do the same thing with the drain plugs. Where did you drill the hole and what size tap and plug did you use? Any pictures?

IMCO sells hex head magnetic plugs. Easier to deal with than the slotted plugs.

Darn, i hope i have better luck with my syringe set up. Sounds like Merc took another shortcut with no drain plug for an item they stress maintenance on. Thanks for the tips!

I take the whole assembly off and change the oil and impeller every winter.