Fuel filter clean?

[rhythmsurfer]

After buying the 1981Hunter 36 (Yanmar) I have put somewhere between 50-100 hrs on the motor. After finding out the fuel guage was not accurate by running out of fuel, I decided to replace the fuel filter. This is what I found. Is the sludge normal? I changed the filter and I have ran the motor since and didn't notice any change in performance. I will now replace the fuel filter every 50 hrs. Is this what a typical fuel filter should look like when changing? Is the sludge normal.

 

[Warren Milberg]

After 50-100 hrs the filters should not have sludge in them. Has the boat been sitting up on the hard or in storage for a number of years with old fuel in the tank? If so, I'd suck all the old fuel out, flush the tank, put in some fresh fuel and then change the primary and secondary filters. Sludge is not normal.

 

[Ron20324]

A 1981 Yanmar with 50-100 hrs on the engine?.

Warren, read the post a second time. He put 50-100 SINCE HE BOUGHT IT.

 

[higgs]

You should be able to get at least 100 hours on a fuel filter if your tank is fairly clean. I do mine every other season and probably put close to 100 hours on each year as I do use the boat a lot. I have, like many boats, two filters. Yanmar has one on the engine, and then a Racor is installed between the tank and the fuel pump. I find sediment at the bottom of my Racor despite the fact that I cleaned the tank out recently.

 

[Benny17441]

That is the secondary fuel filter and to find that amount of sludge in it is not normal. I'm surprised the engine ran well in spite off. What does the primary filter/ water separator look like? That black junk is dead bacteria and the tank is likely full of it. Best remedy is to have the tank drained and the fuel polished. Fuel gauges are notoriously innacurate and since the error is not usually consistent it is impossible to try and learn how to read them. The best way to calculate fuel availability is to determine the engine's average burn rate in gallons per hour. Knowing the size of the fuel tank in gallons will allow you to determine pretty accurately the amount of fuel used if you know the number of hours the engine has ran since last fill up. This is where an hour meter connected to the control panel key switch can surely earn its keep. If you have a three cylinder diesel engine your burn rate should be around 3/4 gallon per hour. That figure can be further refined for your engine. There are a lot of missconceptions about the method but winds, currents and hull conditions do not affect burn rate and an average is used to account for the normal variations in throtle settings. My fuel gauge has not worked in years and I can usually predict within 1/2 a gallon how much fuel will I need to top off the tank. Good luck.

 

[Bill Roosa]

I change my filter based on the amount of fuel they filter.
If I use a gallon of fuel an hour and change out at 100 hours that is only 100 gallons of fuel that have been run through the system. I discount the fuel return and re-filtered as that fuel is clean and would not "add to the filtering load"
Would you change your car fuel filter after 5 fill ups???

To give a reference as to what filter are normally replaced at I'd note that 50K miles is typical for a car fuel filter. If you get 20 mpg that would be 2500 gallons.

I'm thinking that given a boat motor sits idle and you do get "goop" growing in diesel you would be fine if you used a bio "goop" inhibitor and replaced the fuel filter at around 1000 gallons. Your hourly burn would determine how many hours of engine time that is or just count fuel tank refills

 

[Steve Dion]

Bill: I would have to agree with you. The difference may be where and when you get your fuel. If someone is picking up fuel every few years, a filter change every year or so is maybe more in line than someone in line than someone that is refueling two times a year.

I had a fuel issue a few years back and decided that I needed to have a dual filter system in case something happened again.

For most of use changing the Racor (primary filter) every 3-5 years is probably adequate (if you have a clean source and tank). Otherwise every year or two may be called for.

Everyone needs to evaluate their situation for themselves.

 

[Ken Honeycutt]

Better have the tank cleaned and all lines replaced. When I bought my 84 31' Hunter a few years ago I never bothered to check the filters thinking the PO had changed them out. Engine died in the middle of the harbor one day while motoring to my can. Luckily there was a park district boat nearby that caught me before I started bouncing off some very expensive boats. I replaced the filter with a Racor 500m thinking that would solve the problem, but it plugged up again several times with black crud and water. Now whenever I think about it I realize how fortunate this didn't happen when I was close to a lee shore in high winds and waves (a situation I had been in several times before this happen). Like Steve, I have dual filters now and also added a fuel polishing system. If you sail in some rough water it is probably only a matter of time before the tank gets stirred up and more of that black crud shows up in your filter possilby plugging it.

 

[RichH]

No thats not 'normal'. Its fairly indicative that you have a quite severe 'infection' of microorganisms, chiefly fungals (Cladosporium Resinae, etc.) in your tank. To remedy the tank and the distribution lines ... AND the 'vent' and fill line should be thoroughly cleaned; after cleaning a small amount of new fuel should be used and 'recirculation polished'. Then a 'bacteriostat' / anti-fungal stabilizer should be added to any new fuel you use to 'fill' the tank. Even with new fuel and cleaned tank, you can experience 'slugs' of such 'slime' for quite some time, so plan on changing filters for some time in the future until the tank and its distribution lines thoroughly 'clean out' and the tank reaches some level of 'equilibrium'.

Once 'infected' and no matter how well you clean the tank, etc., you will have to use a 'bacteriostat / anti-fungal' additive to keep this 'infection' from returning.

If you want to delve into the cause more deeply, do websearch for 'kerosene fungus' or "Cladosporium Resinae". Has nothing to do with how much water there is in the bottom of the tank.

A simple 'polish' or 'recirculation polish' of your fuel will not be of benefit (and will be a waste of time and money), you must clean out the biological 'slime' and the actual fungal cells growing on your tank walls, and you must use a 'bacteriostat' in your fuel for the long term future.
This is an INFECTION where the funguses are using the fuel as their nutrient source, the 'black slime' is old dead and dying fungus cells and their products of cellular metabolism - cellular 'poop'. This 'slime' will easily extrude through 'filters', does not 'burn' well in the combustion chamber and will eventually result in your exhaust system (manifold) + water injection elbow being blocked by 'coke'.

 

[Bad Obsession]

I have been told to put anti-fungal treatments into the tank every time you get diesel. I also change my filter every year....between 50 and 100 hours on them.

In older boats I don't like to get below a half tank if I can avoid it.

You also may want to check out fuel polishing posts that were on this board in the past. This may not be a bad idea, looking at your filter.

One other thing.....I once helped my Dad and a friend rebuild an old Revel Craft 27. It was gas with a Ford 454. The original fuel tank was galvanized. It was an older boat so it had began to break down. The end result was a rust colored fuel making it to the fuel filter. The end result was the tank was replaced.

 

[rardiH36]

I wonder if the recent/new ultra low sulfur diesel fuel formulation will result in a less bacterial growth problems for boat owners in the future?

This past winter, I replaced my Racor and the on-engine Yanmar filters for the first time in the 4.5 years I owned my boat. Of course, I had inspected them several times in the prior years, but each time they both looked totally uncontaminated and still the original manila folder tan color. The boat is same model and approximate build year as RythmSurfer's. But I am not sure if we have the same engine. (Mine is a 2QM series Yanmar.)

At my 4.5 year filter change, they still looked the just fine same. But what the heck .... it was way past the chronological change-out spec. So just do it -- also because I read that the paper elements can break down with time and sogginess. (I saw no evidence of this however.)

I just mention this as just another example of how very different experiences can be depending on environment and history. Certainly I can't take credit for my clean filters. Nothing radical I did to the tank or fuel. Only possibilities are that I get my diesel from the local Chevron gas station which presumably has a frequent inventory turnover, San Francisco Bay is a relatively low humidity environment, and I do add some "cure everything miracle additive" when I remember with each 5-gallon jug.

 

[Bill Roosa]

Sounds like you folks need to go sailing more often.

 

[Stu Jackson]

Very good options presented here.

If it was my boat, I'd change both filters and check the primary (off engine usually a Racor) after the next 25 - 50 hours, or sooner if you feel like.

All the reasons presented are valid, and only YOU can know what you're seeing on your filters after some more run time.

We also don't know the condition of your tank or the viability of your fuel source.

What was the condition of your primary filter?