Dealing With Diesel
by Phil Peterson

Diesel engines have gained wide acceptance as auxiliary power in sailboats. While the engines have been around for some time, they began replacing gasoline engines as standard equipment in great numbers in the late 1970’s and early 1980’s. They are attractive due to their lower fuel consumption, and reliability. “Give it clean fuel, clean air, clean oil, and keep it cool” the old saying goes, “and it will run forever.” Sure, they are a bit noisier and not as smooth as a gasoline engine, but these disadvantages are far outweighed. Plus, diesel fuel has a lower flash point, and is safer to have aboard.

However, one problem with boats on the Great Lakes is that they are used less than 6 months out of the year. And from my experience surveying sailboats, the average auxiliary diesel is used only 50 hours per year. Some of the smaller diesels may use 1/3 to 1/2 gallon per hour. With many sailboats in the 27 to 36 ft. range having a 20 gallon fuel tank, you can do the math and see that you may barely use a tank of fuel per season. When fuel just sits, contaminates can accumulate, and algae can start to grow in the fuel. While algae in fuel on the Great Lakes is not nearly the problem it is in warmer climates such as Florida, it still occurs on the Great Lakes.

Duel Racor set-up with plastic sediment bowl protected by metal heat shield.

While I had contaminated fuel problems on boats in the tropics, I hadn’t given much thought to contaminated fuel on the Great Lakes, and it had only been a minor problem once in the past 30 years at a local marina. But in 2001 I surveyed a 22 year old C&C 30 that had been sitting on the hard for several seasons. The new owner reported that he had a problem with dirty fuel by the time he got to the Soo on his way back to Lake Huron. Apparently there was an accumulation of dirt in the fuel, and any algae in the fuel had an opportunity to grow during the warm summer months while the vessel was on the hard. Likewise, there may have been water condensation in the fuel tank if the tank had not been topped off during storage. Needless to say, my survey reports now have a recommendation that the fuel be cleaned from time to time.

So what is the best way to keep your engine supplied with clean fuel? You have several options.

First, have a good fuel filtering system between the fuel tank and the engine. ABYC standards recommend at least one fuel filter/water separator between the fuel tank and the engine. But a step up is having two separate filters. The primary is an in line filter that will filter out particles up to 10 microns, and will separate any water in the fuel. A second filter, frequently mounted on the engine, is a secondary filter, which commonly filters out particles down to 2 microns (but check your engine manufacturer’s recommendations!)

If you are having fuel problems, or are heading out on an extended cruise and want to be prepared for getting bad fuel somewhere along the way, RACOR has an excellent setup with two turbo filters plumbed in parallel. The filters have a three way valve which allows the operator to direct the flow of fuel to either the left or the right filter. If bad fuel is encountered, the operator can switch the fuel flow from the dirty filter to the clean filter. Once this is done, the dirty filter can be cleaned, all without shutting the engine down. And that is a great feature, especially if you are maneuvering in close quarters or heavy traffic and you suddenly lose engine power.
A Note About Racor Filters:

Many boat owners like the Racor turbo filters with the plastic sediment bowl so they can see if there are any contaminates in the fuel, which is a good idea. However, if the unit is mounted in the engine compartment, it must have a metal heat shield installed on the bottom of the boat to survive the ABYC 2 ½ minute burn test. Many owners, and possibly marine yards, will install a Racor turbo filter without the heat shield on their boat. It may be used, but only outside the engine compartment. If it is in the engine compartment, it must have the heat shield, and the model number will end with the letters “MA”.

A second way to protect the fuel to your engine is to have two fuel tanks in series. The first tank is filled from the dock. But then the fuel is passed through a good on board fuel filter system into a second, usually smaller tank. While this may not be practical on a smaller boat, it does allow the advantage of having a good supply of clean fuel in the second tank if the filters start getting dirty and start clogging up.

If you discover that you have contaminated fuel in your tank, you can have the fuel “polished.” A high speed fuel pump is hooked up to a hose that draws the fuel out of the tank, through several fuel filters plumbed in parallel, and then returned to the fuel tank through a second hose. The contaminates are filtered out of the fuel, and the high speed pump will churn up the fuel and contaminates and does a very effective job of cleaning the fuel. We needed to do this one time in Florida on a boat as we were returning from the Bahamas. As we were approaching Hawk Channel and were taking down the sails, the diesel engine lost power. We nursed the boat to a marina, where we had the fuel polished. It was amazing what came out in the filters, including chunks of metal, possibly from when the boat was constructed! And this was a boat from a well respected U.S. builder.

Of course, if you have a small tank, you may wish to simply have the bad fuel pumped out and given to someone who heats with used motor oil. The disadvantage is that there may still be some sediment in the bottom of the tank that the single pump out will leave. The advantage of the high speed fuel pump is that it stirs up all the fuel, and has a better chance of getting everything out of the system.

So how common is bad fuel problems on the Great Lakes? Some years ago when I was an excursion boat captain in the Apostle Islands, we would occasionally have a problem with the fuel on an older boat. In this case, it had sediment in the fuel tanks that would get stirred up on days when we had strong winds and were going out around Devil’s Island. We’d make it around the island with no problem, but on the trip back to Bayfield the single main engine would start to loose power. It was necessary to get in the lee of Bear Island, tell the 150 passengers that we were going to take a short break, and then go down into the engine room to clean out the filters. It would have been very helpful to have parallel RACOR filters on that boat. Instead, the engine had to be shut down and then bled afterwards before it could be restarted.

A second time was when a Bayfield area marina apparently received a bad batch of fuel, and several boats had fuel problems. Once the problem was identified, it was quickly cleaned, and everything got back to normal.

In the past several years I’ve been on two deliveries where we had bad fuel. One was a short trip from Bayfield to Duluth on an older 42 ft. sailboat that had been sitting on the hard for 2 or 3 seasons. Before departing, the owner had requested that the marina clean the fuel. We were reassured that the fuel was good, but about two hours from the Superior entry the engine began loosing RPM’s. We checked our speed down and continued on. By the time we were at the Superior entry, we were down to 5 knots, then only 4 knots by the coal dock, and only 3 knots when we arrived at Spirit Lake Marina.

Last summer we took a Mainship 39 to the Soo. During sea trials, the boat listed to port, which we attributed to the non-functioning trim tabs that were repaired before the delivery. However, on the trip to the Soo, we noted that once again, the boat was developing a list to port. We stopped for fuel in Copper Harbor and checked the trim tabs, which were operational. We did some more experimenting on the way to the Soo, and concluded that the fuel return line was going into the port tank, and the cross over hose was likely blocked, preventing the starboard tank from equalizing. This was confirmed after the boat reached its final destination and the owner had a chance to take things apart.

So how concerned should you be about your fuel on the Great Lakes? The fuel on the Great Lakes is generally very clean. And if you have a fuel filter with a plastic bowl, you will be able to monitor the condition of your fuel. Of the 100+ boat that I inspect each year, only a very small percentage have an accumulation in the sediment bowl. But if you don’t have a fuel filter with a clear plastic sediment bowl, or are purchasing a boat that has been sitting for a season or more, give serious consideration to having your fuel polished so you know what you have in your tank.

About the author: Phil Peterson is a marine surveyor, and has been in the marine business for 35 years. He has experience in sales, as a yacht and delivery captain, a marina manager, and is a Certified Marine Surveyor, and a member of the National Association of Marine Surveyors. He holds a USCG 100 ton near coastal license and has logged over 80,000 offshore miles on fresh and salt water. He is from Bayfield, WI.



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