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What’s in your tank? Adding an Inspection Hatch & Marine 16’s Diesel Fuel Complete

One area of the yacht that we had not fully inspected was the fuel tank and after four years of ownership we wanted to see what we were dealing with. With a near empty tank now was the time to try and take a look.

Diesel bug can lead to all sorts of problems including clogging filters and causing the engine to cut out. Equally crud and sludge build up in the tank could cause similar problems. One thing we wanted to install was an Inspection Hatch to allow us to gain access easily to the tank in future should we ever have an issue. We opted for a Wema Inspection Hatch from Tek-Tanks, a two part inspection plate suitable for diesel tanks. The recommended hole cutout size is 112 mm however we found that a 110mm hole saw was ample to cut the hole and fit the hatch.

So what was in our fuel tank? Well, as you can see below, we had a handful of black sludge lumps, and some rather weird “crystalised’ fragments. We’re not sure if this is related to Diesel Bug but didn’t really like the idea of it being in there!

Black Lumps in Diesel Fuel Tank

We extracted the remaining fuel and cleaned the tank with some blue rolls.

With 4 Jerry cans of fresh (and now much more expensive!) diesel we half filled our new clean tank and added Marine 16 Diesel Fuel Complete (£ 23.95 from Marine Superstore). The idea is that this prevents the growth of diesel bug and combats all of the effects of using biodiesel and ultra low sulphur diesel. It also works its way through the engine, cleaning and lubricating, which should help improve fuel consumption and reduce emissions. You only need a small amount – 100ml per 100 litres of fuel, and overdosing will not harm your engine. But bear one thing in mind – this stuff stinks!

Only time will tell how effective this stuff is. So far we have only ran the engine for around an hour but she seems to be ticking over nicely. We’ll update this blog later on to let you know how it’s going!

Marine 16 Diesel Fuel Complete

Update one year on!

We’ve been using Marine 16 Diesel Fuel Complete for the past year now and were interested in what our tank was looking like. With the benefit of now having an inspection tank, and being down to the last 20 litres or so of fuel in the tank, we decided to take a peak inside and this is what it looked like:

Clean Fuel Tank

As you can see it’s looking pretty good. You can actually see the reflection of the top of the tank! We decided to extract a couple of litres of fuel from the bottom using a Siphon Hand Pump to get a closer look. Water is denser than diesel so if there was any water in our tank it would have settled at the bottom. The first image shows what we extracted and how it looked after sitting for one hour. As you can see the fuel looks in great condition with no obvious signs of any water, diesel bug or any other form of contamination. Out of interest we poured a little red diesel into a bottle with a little water, gave it a good shake and waited to see what it would look like. After just a few minutes the water and diesel separated, which you can see in the second image.

Red Diesel
Red Diesel with water in it

This inspection of the tank and fuel after a year settled any concerns we had. We were confident that there was no water in the fuel and it appears that the Marine 16 product was working well so we’ll continue to use it moving forwards.


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