Re: oil pump selection
 

I would probably try to avoid the merc pump. I know the pump they use on the 500efi and 525efis have the gasket under the top cover. In my mind this is something I always avoid and replace with a better quality pump that is a machined fit. Such as Melling. I am not sure who makes these pumps I would assume it is a GM part #.

Re: oil pump selection
 

The Melling punp is about 40.00 from any auto parts supplier. I hate to think what Mercruiser sells it for, probably a couple hundred. Go with the Melling and a new pick up. Weld or braze the pick up.

Re: oil pump selection
 

Tack weld with NI-rod. Brazing with torch makes too much heat before the bronze flows. --- Jer

Re: oil pump selection
 

M77 Hv . Do yourself and your motor a favor and deburr the gears inside on a wire scratch wheel or file by hand. This will help keep the pump from wearing itself out. BBB

Re: oil pump selection
 

By using a high volume pump do I have to worry about high pressures and stock clearances. I have got the block assembled and balanced so opening up oil passages is out. What is a NII rod in welding? Will a wire fed mig do?

Re: oil pump selection
 

Mig is no good for that. Ni rod is nickel. Pump manufacturers suggest taking the pump apart to weld, I have good luck just tack welding with a 55% nickel rod. Forney sells a good rod and you can get 'em at any Ace hardware. for apx $5 for a pack of them. Also make sure you use a big enough pan in order not to pump all the oil out of the pan before it returns back down. BBB

Re: oil pump selection
 

I will be using the stock stamped steel oil pans. When starb. motor left it took the 14 qrt oil pan with it. After pricing these I decided to run the stock pans on both new engines. Everything is starting to come together now but at the point of selecting oil pumps. I was told not to run high volume if I had not opened up oil passages. Any insight on this?

Re: oil pump selection
 

The oil pump number I gave you is high volume and stock pressure. All I've ever used with no issues. Big or small block.