While we have been enjoying the warmer weather in the SE, we are currently in Key West, our diesel fuel has been hard at work creating sludge and what is called asphaltenes, http://fuelschool.blogspot.com/search/label/Asphaltene.
Fuel as a biologic substance is affected by many factors including temperature, moisture and contaminates. Aside from routine maintenance, most engine problems can be traced back to fuel management. Particularly problematic after sitting for prolonged periods and then going out in seas that agitate the fuel.
This causes all of the gunk that has been formed and is sitting on the bottom of the
fuel tanks to become suspended in the fuel which is then picked up by the engine and run through the filters. The filters, made by Racor do a very good job of filtering and separating out the water, but you can overwhelm them with dirty fuel and water.
The potential is for clogged filters which shut the engines down and or smaller particles accumulating on the injectors which over time cause performance deterioration as well general fouling of the injectors. Additionally, water accumulates, often the result of condensation from temp changes or it was present in the fuel when it was sold.
The longer you sit the greater the risk, conversely the more you run the boat and "turn over" the fuel the less the problem.The other risk is getting dirty fuel from either bad storage tanks on shore or where the fuel has sat too long before being sold. We try to find places that have high turnover of fuel and the facility is visually, at least in good shape. When traveling in more remote places, that option is not always available however. Fuel sold outside the US is sometimes more suspect also. Whenever we take on new fuel it is a good idea to run it through the polishing system.
To help manage this problem last year we installed a "fuel polishing" system made by ESI
Our ESI fuel polishing system is mounted on the forward bulk head of the port side of the engine room. We can polish (filter) about 180-200 g/hr. We can filter the fuel to 2 microns.
The reason is the fuel pick up tubes draw from the bottom of the fuel tanks returning the filtered fuel to the top. To ensure we have a filtered all of the fuel I like to do more than is needed. We will in essence filter 2250 g. of fuel in tie next few days.
I will try and address each system in future notes and cover with greater detail.