Which micron?

[Angela]

I have Racor primary filters on both the engines and the genny. I've been buying the same fuel filters for my primaries that were on the boat when I got her. But, what SHOULD I be using? The engines have 30 micron in them while the genny has 2 micron in it.

We go through a lot of filters on the genny's Racor, but so far only one of the tiny filters that's on the engine (that's the secondary, right?). On the engines, I just bought new secondaries and am switching from the original "element in a can" to the spin-ons. I have no idea when the last time those were changed, but I'm changing them now.

I don't know how bad the fuel might be. Ed is building us a portable polisher that we can share between the two boats. The when the genny's primary gunks up, it's like a tar baby when we pull it out. There were times, not lately, where we would go through a primary in about 30 minutes - I wonder if we were dipping out tank that was getting empty - don't remember. However, we always have to change the genny filter at LEAST once when we're out for a weekend, and sometimes more. It usually occurs in the middle of the night, too. The engines' filters have never been this bad nor this annoying. The engines and the genny are running off separate tanks - engines on the aft; genny on the forward.

[Pascal]

i have 30 microns primaries on both the genny and mains, pretty sure the secondary are 2 microns, or maybe 10... not sure off hand.

i really think 2 microns primary is too fine, that's why the genny is gettting clogged so quickly.

if you're only using the forward tank for the genny, your fuel is not getting used quickly enough. i run one main and the genny off the forward tank (larger), the other main off the aft tank; this way both tanks are being used.

[Nonchalant1]

Definitely 30 Micron for engines and genny RACORS. The secondary on Detroits is 2 or 3 micron I believe. Just buy the recommended DD secondary fuel filter from DD or call them and ask the filtering size for your engine. It only comes in that one size I believe.

Your genny filter has plugged up fast because it's too small in micron size. My Onan has 30 micron RACOR and a 3 micron final filter, which has not needed changing in 3 years. The idea is that the RACOR catches all the big sludge and everything down to 30 microns and then the final, smaller, filter only has to deal with particles between 29 and 3 microns in size. Almost everything is bigger than 30 so the final filter lasts longer.

I only changed final filters 2 times in 6,000 miles during our Loop trip, once before we left and once about 4,000 miles later. I knew it was time to change them because even with clean RACORs one engine's top RPMs kept slowing down until it would not go faster than 1600 RPMs. (sound familiar?) When I changed that little final filter, the engine went back to full performance instantly.

Doug

[StratPlan61]

Ang, I agree with Doug, I think 30 microns is good for everything. Passagemaker magazine had a good article about this last year, it might be worth looking up and reading - I found it quite very informative. There a couple schools of thought about it, but I think Doug catured it well.

[Angela]

Well, that certainly explains the genny filter nuisance! Thanks.

[Brian Degulis]

Your genny is cloging because the fuel is contaminated. The idea behind 2 micron primaries is that you trap all the dirt in one filter that's typicaly easier to change than the engine mounted secondarie. The down side to it is that because your using one fine filter instead of a course and a fine is that you know have only 1/2 the filter area so it clogs faster. So do you want to change 1 filter twice as much or 2 filters less frequently.

The idea that theres something terribly wrong with a filter that traps dirt is pretty silly that's what it's supposed to do. If it's clogging to often then the filter is to small or the fuel is contaminated. If you go to a 30 micron primary and a 2 micron secondary assuming both are around the same size it will take twice as long to clog but you will have 2 filters to change. If you used a 2 micron primary that was large enough to have the same filter area as the primary and secondary combined it would take about the same amount of time to clog.

I use 2 micron primaries because I don't want to change the on engine secondarie on a routine basis because it's more dificult. If I have a fuel problem I know wich fiter it is my vacum guage warns me the filter is cloging with the 30/2 setup the vacum guage tells you nothing about the secondary. As a matter of fact a pluged secondary reduces flow and actually lowers the vacum reading leading you to believe all is well when it's not

So Ang it simply comes down to filter area and which filter is easier to change and how much you want your vacum gauge to tell you. But the first thing you need to do is get the fuel cleaned up or replaced. With clean fuel my 2 micron primaries are good for 150-200 hours.

Brian

[captddis]

I am with Brian! The 30 micron business is nonsense. If your filter is plugging it is doing its job! Why run all that crap through the pump and lines only to clog the on engine secondary first. I use 10 micron filters it seems to be a happy medium and does not plug the secondary. The problem is a lot of builders do not install filters with enough capacity. Most of our boats should have dual racors and you can run 2 micron elements using both filters.
The only way I would use 30 mic primaries would be with staged filtration.
If the fuel is fouled, get the tanks cleaned and solve the problem. Detroits need a good flow of fuel for cooling and lubrication. If the filters are always plugging and starving injectors, problems show up down the line.

[SKYCHENEY]

2 micron is the way to go, but only if you have dual filters with vacuum gauges. This way you won't starve the engines for fuel as you will see when to change the filters. You also have the ability to switch to a clean filter immediately when the need arrises and you can change the clogging filter at your convenience.

[Roscoe]

Angela: The aromaticity of diesel fuel allows asphaltine molecules ( or diesel sludge) to remain in solution. Diesel loses its aromaticity as it ages and the asphaltine molecules then clump together and precipitate out of the fuel to form sludge. This is what is clogging your filters. It is the result of low fuel turnover and will continue building.

The best solution is to clean your tanks and then use a sufficient quantity of petroleum solvent to keep low turnover fuel asphaltines in suspension so that diesel sludge does not reform. Petroleum solvent is commonly sold as fuel conditioner at great markup ( and great promises of mysterious additives which are mostly bunkum)but can be purchased commercially.

If you cannot clean your tanks, use the petroleum solvent and polish your fuel. It may be more cost effective and less work to clean the tanks.

[Will]

I also have 30 microns for primaries on the mains and a 2 micron for primary on the generator. I believe it is the OEM configuration and have always wondered why? With my limited knowledge of things, it seems that both the mains and the generator (which also has secondary and tertiary fuel filters) should have the same 30 micron, primary filters. Does anyone know the thinking behind the OEM configuration?
Will