Considering a sailing adventure to Mexico? Just look at how engrossed that guy is in the book! Grab a copy of the Unauthorized Guide to Sailing in Mexico, and you too can find yourself sitting on a Mexican dock with an oversized (but very attractive) hat.

Unauthorized Guide to Sailing in Mexico

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Wednesday
Jan182012

diesel microbes doing their thing

Gross. Click to enlarge.Water ends up in a diesel tank, and up to 27 different types of bacteria can live in the barrier between the two fluids, essentially "eating" the diesel. As much as that grosses me out, I have to admit that's some pretty hardcore bacteria. I mean really, could you eat diesel?

Last year I cleaned out the tank (act one, act two) and although there are lapses in maintenance overall I'd say I keep the fuel system pretty clean.

On my twin Racor setup one of the filters was getting a lot of use and the other essentially sat idle for a year with a bit of water at the bottom. I'm not sure how many of the 27 strains of bacteria grew in that bowl, but you can see for yourself in the picture below that the gunk was pretty foul. 

Beyond cleaning your tank, there's a lot of debate about how much the "keep your tank full" wisdom really matters. Having less fuel doesn't allow more water to condense; the water is in there or it isn't. Regardless, a good biocide is in the cards. 

The only biocide that Yanmar recommends is Killem FPPF, I'm assuming because it acts in the water area and not the fuel. So if you have a water separating filter (like Racors), the biocide itself should never get into the engine. 

While I'm on my soap box, let me bash "fuel polishing". I aimed a garden hose full blast at the crud in the bowl there (which is very similar to what's on the bottom of most diesel tanks), and maybe 90% of it came off. And that's full blast with a garden hose. Fuel polishing achieves nothing like that type of pressure or agitation, and as such will even get worse results.

It's simple: if you have crap in your tanks you need to clean them out. If you clean them, you don't need to polish your fuel. And polishing your fuel won't clean your tanks. The logic is unfailing no matter how much anyone out there wants to convince themselves why they don't need to potentially cut access ports in their tanks and clean them out. 

Reader Comments (1)

Eric, regarding your post on water in your diesel, the reason to keep your fuel tanks full is to have less air in the tank. I am a professional truck driver, and have learned thru the years from various trucking publications, personal experience, and mechanics I have dealt with in the past 31 years these simple facts. While there may be water in your diesel fuel already, by keeping the tank full or at least above 1/2 full the amount of air in the tank is less. Air has water in it. I don't know about the engine in your boat but the vast majority of diesel engines in semi trucks don't burn all the fuel that is delivered to the engine. The un-used fuel is returned to the tank, but since it is warm it will react with the cold fuel in the tank, creating condensation. When the tank is half full, it will literally rain inside the fuel tank. Since I've been keepimg my tanks over 1/2 full my filter problems have almost become nonexistent, and intervals between filter changes have been extended by almost double. Quality fuel is also very important. While I'm here I would like to say your journal is excelent, and your posts on cruisers and sailors forum are very helpful. My wife and I have our eyes on a Union 36, and use your site among some others to get important 1st hand info. Whatever type boat we end up with the information found here will be a great asset to us. Thanks, Vince and Julie Bednar, snowed in, in Ohio

February 12, 2012 | Unregistered CommenterVince

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