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old diesel fuel still ok?

wenders

New member
Just bought a boat with 2 Lehman 135 engines. Problem is, the boat has been sitting with tanks half full for 2 years.Am I looking for trouble running the boat as is? Would it help to add more fresh fuel or is there some additive that would freshen the fuel?
 
I've started many diesels that sat for extended periods. Some in mothballed ships with diesel many years old. Probably not a problem. Tanks will have some water in them from half full tanks. Make sure you have a good primary fuel filter like Racor. One that separates the water. Add a fuel conditioner. I use Archoil AR6000. It helps combustion and increases mileage of good diesel. I run it all the time in my diesel pickup and got about 10% better mileage. I just started using it in the boat, but get better cold weather starts. Available online.
Add a conditioner, add some new diesel, make sure all linkage moves freely. Whatever additive, make sure it kills fuel bacteria. Leave existing filters for a few hours after the conditioner. No use plugging new filters (if it's going to happen). If you don't have a gauge between the primary and fuel pump, add a vacuum gauge. It should show zero and gradually increase as the filter catches debris. 0-15 or 0-30 (inches of mercury) is plenty. Once the tanks clear up and you buy clean diesel, you'll find you can go much longer on filter changes using the gauge as a guide. Carry extra fuel filters!
My current boat sat for 6 years before I bought it. 2 mains and 2 generators. That's what I did. At the time I used Algae-x and carried extra filters. No problems in 600 mile ocean trip home. I've been running diesels since the late 1950s.
 
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