1930 Diesels - Final Fuel filter micron count?

[SV Simple Life]

I have two 1930 Superior Diesels powering the boat I bought last year. I found a selection of fuel filters on board. I'd appreciate any input on what I should use for the final filter.

The fuel goes through a large, unlabelled water separator, then on to two Racors.... first is a 900, which has 30-micron filters. Then on to a 500FG, which had 2-micron filter fitted. I'm worried that this may be too fine, and may restrict flow?... The engines don't seem to suffer from fuel starvation, so I guess all may in fact be ok. Still, a lot of manufacturers say that 2-micron filters shouldn't be used anywhere in the fuel system.

Any input?... Thanks.

[Florida Mike]

I personally don’t believe there is ever too much filtration. That being said back in 1930 there was most probably very little filtration for those engines. 5 microns would most probably be more than sufficient. I would be more concerned with lubrication of the pumps with the new low sulfur fuel. I personally am 1 ounce per gallon of outboard motor oil to my fuel. I chose outboard motor oil because it is designed to burn. Many other people I know just add motor oil in about the same quantity. Keep in mind that I also believe in getting the fuel off the bottom of the tank as opposed to several inches above the bottom. My reasoning behind this is to get the crud out of the tank in small quantities rather than wait for bad sea conditions to stir it up and clog up the filters at the most inopportune time. Just my two cents, Mike.

[SV Simple Life]

Thanks Mike, Good point on the pump lubrication: I assume you mean the injector pump assembly, which is gravity fed from the tanks? This has its own lube system, which I keep topped up and clean. Cheers, Eamonn.

[hellosailor]

I think Mike has a point. Was anything made in 1930 built to a 2-micron tolerance?

And OTOH, there's no such thing as "too clean" unless it causes other problems. If you have a vacuum/pressure line on the fuel system, and the 2-micron filters are not obstructing fuel flow, by all means keep them. If they are causing a blockage, go up to 5 or even 10, see what works for you.

"No grit" certainly is the best way to pamper any engine, but there are practical limits to how many filters you can cascade, and how often you'd have to change them in order to prevent blockages.

Either way, there should be a guage in your fuel lines, so you can tell "for sure" when then filters are getting blocked and the flow reduced.

[Cheechako]

I think you will get differing opinions on the 2 micron. I had a mechanic tell me not to use them once, not sure if that means anything though....