Gas in raw water pump oil reservoir

[PAUL22]

Hi all,
(merc 454 7.4l 1996 of809461 with bravo iii)

last yr. I serviced the oil reservoir in the raw water pump , and found some gas mixed w/ the oil. (i have the mechanical fuel pump that sits on top of the raw water pump). There was never any gas in the clear tube to the carb. I changed the mechanical fuel pump.

This year, i serviced the raw water pump, and again found gas mixed w/oil! The clear tube does't have any gas going to the carb.

It appers to be an enginering design flaw. Can i do anything to prvent this problem?

Tia

paul22

p.s. Thanks to all the fine people who have posted on this site, i have learned lots and fixed several issues over the years. (hydrolock, bellows ,gimball bearing,allignment,u joints, shutters, impeler, lower unit service, etc.)

 

[Don S]

Re: Gas in raw water pump oil reservoir

It appers to be an enginering design flaw.

Yes it was, right up there with a 470.
Every fuel pump leaks a slight amount of fuel into the oil pan from a block mounted fuel pump. But it's a large space and never noticed. But Merc decided to put it into a 600 dollar housing so it would need replaced every couple years.
If your pump bearings are still good, put in new gear lube and make a cover to block it off.
Then install an electric fuel pump with the proper oil pressure switches and plumbing and never have to spend 1200 bucks again for a fuel and water pump change on a big block.

The proper marine fuel pump should be wired in like this.

 

[PAUL22]

Re: Gas in raw water pump oil reservoir

Thanks don s.

I"ll look into that. Any suggestions on the pump and where i can get it?

Paul 22