Fuel Filtering or Cleaning

How does the filters look today when you run the engines? More fuel in the tanks use to mean less water.

Diesel oil should not be left to sit for years, it does go bad over time, there are actually types of fungi that can live off of nothing but diesel, but a few months is fine.

Did someone actually do any type of diagnostic step? Draw some fuel and take a look at it or somehow examine the inside of your fuel tank? If the answer is no, I think it is safe to say that some Marine Mechanic is just trying to make a quick buck.

I would consider fuel filter examination a diagnostic step. How much have you run your boat since you changed the filter? If you made one run of a few dozen miles then absolutely that means you have a problem, if you ran all day and night with reckless abandon then your fuel filters being dirty isn't that much of a surprise.

If I remember the song correctly Catalina is 26 miles of open water each way. That over 100 miles, plus "a few times up the cost to Malibu and back". I'd be surprised if your primaries weren't 'dirty' and am surprised that you secondaries aren't a bit. Sounds like your mechanic is looking for work. Do put in some fuel stabelizer and anti-fungal. Adding a pair of Racors is never a bad idea.

You might enjoy this.

It is best to keep the tanks full. Algae needs heat, air and condensation in order to grow in diesel fuel. If the tanks are full there is much less air in the tank as well as condensation.

Do not cut access plates in your tank.

If your filters have gone through an entire season and are just now dirty, it's not nearly that bad. If you're changing racors every 8 hours thats a different story. If you're going 50hrs between primary filter changes the algae is not that bad, and if you've been in rough seas the sloshing broke free the algae on the walls of the tank. Add a product called "Diesel Kleen" it comes in a grey bottle and will eat the algae.

Fuel polishing is a complete waste of time and money. Only 90% of the algae is removed. Then if you don't go through that old fuel within weeks and add a good additive, it spreads right back to where you started from in a months time. It will also spread right through new fuel that you've added after polishing just like cancer. Adding a good fuel additive such as Diesel Kleen that eats the algae is your best bet. DO NOT use a biobore like pri-d or the others they will kill the algae and it all will end up in your filters.

It sounds like you need a more knowledgable mechanic. I wouldn't worry about algae hurting your injectors. Maybe if you had a TERRIBLE algae problem and you're filters were completely clogged and you're pulling 20+ inches of vaccuum it might stress the injector pump or injectors...... Water in the fuel, however will kill injectors.......

Also you want to check your vaccuum reading while you're at cruise and pulling a normal amount of fuel through the filters. If you see 15lbs or so, change the primaries.

I have learned from trial and error, if your tanks are dirty, the only thing that can be done to correct the situation is to have your tanks manualy cleaned. Seperating fuel is more of a maintenance thing to keep the water out. Adding biocide to a dirty tank makes more of a mess of an already messy situation (it breaks it all up).
If you don't clean your tanks, you will be changing your filters on a hot engine in rough sea's.. as that is when it gets all stirred up and specially formulated to ruin your day, or night at 2 AM as that is when alarms always seem to want to sound!

You have got Racors. You would do well to change the T-bar for a guage. RU finding much gunk in the bottom of the Racors?

Might pay to know...

...what size filter elements are in the Racors--20 micron? 10? 2?

One point not mentioned.

It is hard to know how fresh or clean the diesel is from the fuel dock. You can guess that a busy fuel dock turns stock over faster but there is no way to know for sure.

Therefore, you could go through the entire process and get bad fuel pumped back in the next time you fuel up.