Fuel filter questions

[skipperpete]

Recently a friend of mine had a serious diesel injector pump failure (seized hydraulic head on Perkins 4-108 DPA injector pump)and after she’d finished the repair asked if there was any way to stop this happening again and leaving her adrift at sea waiting for a favorable breeze. Now, I know the general opinion on this forum regarding fuel filters is that there should be a 10-15 micron primary and a 2 micron secondary but I unrepentantly told her that the best way was to only use 2 micron for both primary and secondary........ok, put down the pitchforks and hold off for a moment with the google search until I state my case.
1. This boat is in a region not well known for clean fuel availability
2. Usually no reliable dockside refueling
3. Fuel transported to the boat in 20litre jugs.
4. Many folks have very old fuel of dubious quality in their tanks.

I maintain that the ONLY goal is to make sure that fuel cleaned to 2 micron ever reaches the injector pump and I don’t mind changing a lot of primaries to make sure that the secondary remains pristinely clean and not semi blocked by all the all the 14 micron crap that the primary lets pass. I suggest that the primary filter be a big one to avoid high negative pressure in the suction line and that it be an easy filter to replace and bleed. If you have a common rail engine it’s even more imperative that only ultra clean fuel makes it to the HP pump.
Racor and most of the popular filter manufacturers recommend the 15-30 micron primary and 2 micron secondary so I’m swimming against the tide here but I definitely think a big ol Caterpillar 2 micron spin on as a primary beats a little 15-30 micron Racor hands down for both price and efficiency.
Interested to hear the views of cruisers who have actually thought about this and if anyone on the planet agrees with me. [ATTACH].
Here’s what 2 micron looks like.

[Renoirpierre]

Not a cruiser (yet) but a decent shade tree mechanic. I think the 15-30 micron filter will prevent the frequency of plugging of the 2 micron filter.

If you have two 2 micron filters in series then the first one will likely do all the filtering and will plug up while the second one will not do much (any) filtering.

[S/V Illusion]

Putting dirty fuel into series connected 2micron filters guarantees faster fuel starvation and breakdown, the very thing you are trying to avoid.

Simply adding a vacuum gauge to the primary will show when a problem begins.

[skipperpete]

Originally Posted by Renoirpierre

Not a cruiser (yet) but a decent shade tree mechanic. I think the 15-30 micron filter will prevent the frequency of plugging of the 2 micron filter.

If you have two 2 micron filters in series then the first one will likely do all the filtering and will plug up while the second one will not do much (any) filtering.

Yes, I agree and I’d rather replace just the one filter than both. I’d prefer to avoid too many interventions with the secondary. If there’s space available I’d like to have a second primary in parallel with a selector valve ready to go to when the first primary blocks up as it inevitably will.

[Marathon1150]

I use a 2 micron primary and a 2 micron secondary on a Perkins 4.108. I have been doing this for more than 15 years and adopted the practice when a well seasoned boat neighbour asked me "which filter will you change when it seems that one or both are clogged"? The primary filter is a Racor 500 and can be changed in less than 2 minutes at least partially because of the small electric pump that was installed to fill the housing after a filter change. The secondary filter is a canister and more often than not, the lines need to be bled after a change. This is a major pain on a Perkins 4.108.

The primary has a vacuum gauge fitted downstream and only indicates an issue when bad fuel has been used. Or, when someone leaves a paper towel in the fuel tank after a fuel polishing job. This happened a couple of years ago and was a major problem - the primary would work for about an hour before it needed to be changed - this was on the way to French Polynesia and led to a one day longer trip than hoped for.

Since then (2019) and prior to then, no problem using a primary 2 micron filter.

[donradcliffe]

Originally Posted by Marathon1150

I use a 2 micron primary and a 2 micron secondary on a Perkins 4.108. I have been doing this for more than 15 years and adopted the practice when a well seasoned boat neighbour asked me "which filter will you change when it seems that one or both are clogged"? The primary filter is a Racor 500 and can be changed in less than 2 minutes at least partially because of the small electric pump that was installed to fill the housing after a filter change. The secondary filter is a canister and more often than not, the lines need to be bled after a change. This is a major pain on a Perkins 4.108.

The primary has a vacuum gauge fitted downstream and only indicates an issue when bad fuel has been used. Or, when someone leaves a paper towel in the fuel tank after a fuel polishing job. This happened a couple of years ago and was a major problem - the primary would work for about an hour before it needed to be changed - this was on the way to French Polynesia and led to a one day longer trip than hoped for.

Since then (2019) and prior to then, no problem using a primary 2 micron filter.

I'm surprised it took 5 posts for someone to come up with the real reason for using a 2 micron primary filter.

[Searles]

Why not just clean the fuel tank ,s and the fuel lines ,solves all the guesswork on filters ,do it one do it properly .⚓️⛵️

[Marathon1150]

Originally Posted by Searles

Why not just clean the fuel tank ,s and the fuel lines ,solves all the guesswork on filters ,do it one do it properly .⚓️⛵️

In Mexico I try to filter every drop of fuel that goes into the tank. The filter funnel is slow and sometimes the lineups are long and the vendors impatient. Its hard to know if and when bad fuel will end up in the tank. The double 2 micron system helps prevent surprises at the worst possible time. If I had the space, I would install two primary filters, each 2 microns, with a quick change selector valve as mentioned in a previous thread.

[Pete7]

Originally Posted by Searles

Why not just clean the fuel tank ,s and the fuel lines ,solves all the guesswork on filters ,do it one do it properly .⚓️⛵️

Given SkipperPete's location and the need to jerry can fuel to the boat, I would suggest one of those large filter funnels as a start point and replace the seal in the fuel filler cap regularly.

We don't have a fuel problem in the UK, but it is rather damp, so new seals every couple of years is worth the minor cost to reduce the need to clean the tank out.

Pete

[Scubaseas]

Is the fuel low sulphur? In the States there is nothing but low sulphur fuel. Which early injection pumps do not do well with. Add a lubricant. Most diesel fuel conditioners/treatments will have supplemental lube in them to account for low suplhur fuel.

Vacuum gauge and lots of 2 micron filters is one way to do it. Personally I would rather stop most of the crud in a 10-20 micron primary but the ease of changing as pointed out in post #5 is certainly a consideration.

[sailingharry]

So I'm a bit of a counterculture cantankerous old man with my own views. Kind of like most sailors! LOL

Here's my counterculture view.

Yanmar provides a huge document on installing operating and maintaining their engine. They show one filter. A stupid little engine mounted filter, with unknown specifications, no vacuum gauge after it, no water drain, no clear bowl for inspection. Some hint that it might be 2 to 5 micron, but I have not seen definitive specifications for it. They certainly don't talk about primary and secondary filtering.

So along came sailors and decided that wasn't sufficient, so we added a big Racor in front of it. Then we had to come up with funny words like primary and secondary. And we had to explain some rationale for why we designed it that way, when we didn't really design it that way. We just installed it that way.

My boat came to me with a pair of Racor filters in parallel with a selector valve. And the stupid engine filter. The engine filter had to come off because it was in the way of my second alternator mount and I couldn't find a place to put it.

So I now run just the Racor. Fuel comes from the fuel tank, through a utility electric pump, to the pair of Racors which are 2 micron, and then to the engine. In my view, this is an order of magnitude better than what Yanmar recommends, so I don't feel bad. My Racor filters have a vacuum gauge, and with selector valves I can shift to the second filter in mere seconds. I tend to get 100 to 150 hours out of a Racor filter.

It would be interesting to see what filtering regimen is used on big diesels like over the road trucks and big construction equipment, stuff that was assembled with the intent of using an external Racor. Do they use a big industrial filter, call it a primary, and then a little spin on filter as a secondary? I suspect not, but I truly don't know.

[SY Harmony]

Filtration discussions are almost as bad as oil discussions.
It’s all dependent on the fuel system of the engine. As a rule, electronic engines need more than mechanical.

While Yanmar only ships the small engine mounted filter. Their instal manual does recommend additional filtration. Same with all the brands.
As far as equipment, they usually have longer service intervals and multiple filters and/or water separators.

[Avionics_Joe]

Don't let bad fuel get into the tank! Use a Baja filter: https://www.amazon.com/Mr-Funnel-AF3...a-304695177827

This removes ALL of the contaminates from the fuel, even water. I also have a pre filter slash fuel polisher that uses the same technology and I have never had a problem with fuel on this boat.

[capt jgw]

As previously stated if both filters are the same rating, the secondary will never see any dirt and theoretically will never need changing. I ran a Yanmar 2GM that way for 15 years and never had a problem. BUT, the fuel dock I used had good clean diesel and my tank was brand new so there wasn't much dirt to filter in the first place. The Yannie had the cartridge secondary that you could actually inspect and I did that probably every other time I changed the primary. There never was any dirt in the secondary and as I remember I only changed it once the whole time I had the boat and that was after the first season I owned it.
If the fuel or tank is dirty a 2m filter will plug up quickly and at the worse possible time, probably in heavy weather. Rough water will stir the tank and raise the crud off the bottom. Not the time you want to do a filter change. In that case I'd go with the courser primary. The downside is you then have to change both filters every time.
Another common problem not really related to the original post is if there's a screen on the tank pick up tube. A lot of tanks have them and they're absolutely stupid. The screen will plug up first and stop the engine, and sometimes even good mechanics won't be able to figure it out. All the filtering should be done in the two removable filters where you can get to them. It's worth pulling the pick up tube out and cutting the screen off if there's one there.

[sailingharry]

Originally Posted by Avionics_Joe

Don't let bad fuel get into the tank! Use a Baja filter: https://www.amazon.com/Mr-Funnel-AF3...a-304695177827

This removes ALL of the contaminates from the fuel, even water. I also have a pre filter slash fuel polisher that uses the same technology and I have never had a problem with fuel on this boat.

Yes! I have and use one of these. While I don't usually (ever?) use it for a direct fill from a fuel dock, I find it exceptionally helpful when filling from 5 gallon jugs, as it not only filters but makes a much larger "aim point" for the jugs. For me at home, the 5 gallon jugs are easier than a fuel dock, and usually $1 or more a gallon cheaper as a bonus.