Diesel Fuel Additives

Today’s diesel fuels are not what they seem. On the one hand, the new ultra low sulfur diesel would seem to burn more completely and with less emissions that the older diesel fuel. That may be true under some conditions, but more often it actually doesn’t burn as well. Old fuel is presenting more problems than ever before. I believe that the newer fuels have a much shorter “shelf life” than older fuels, not that it was that much better before.

We are seeing more blueish smoke on start up from all brands and types of diesels. Particularly, on higher performance engines (turbocharged/intercooled) the smoke is prevalent not only at start up, but at light loads even after the engine has warmed up. What is causing the smoke is a lack of cetane. The cetane rating of a fuel is somewhat like octane is to gasoline, but inversely. In gasoline, the higher the octane, the more difficult it is to make the fuel spontaneously explode due to heat. The higher the cetane rating of diesel fuel, the easier it is for the fuel to be ignited by heat.

What this means to the engine is not so easily explained. Here goes nothing. When the piston of a diesel engine rises toward the cylinder head on it’s compression stroke, the fuel is injected slightly before it reaches the top. The fuel ideally should start to burn immediately after it is injected into the hot compressed air. If it doesn’t, two things happen. First, the fuel starts to collect in the combustion chamber until the temperature reaches it’s ignition point. When that happens, all the fuel burns at once, making a “bang” in the cylinder. This makes the engine very noisy. Second, as the fuel isn’t burning, it may come in contact with the sides of the combustion chamber. The fuel that touches the metal is “quenched” and doesn’t burn with the main charge. When the exhaust valve opens and the cylinder pressure drops, this fuel evaporates, making the blue smoke that you see in the exhaust.

By adding a cetane improver, you make the fuel ignite at the proper time and all types of emissions are reduced. You engine will have more power, be more efficient, and have fewer operational problems.

Fuel Filters

Here are some examples of fuel filter elements in different stages of life. We recommend that fuel filters be changed at least every year or 100hrs. If the filter, when you remove it, looks anything like the two lower photos, you should reduce the time between filter changes.

The elements below are just one type of fuel filter element, your vessel’s primary filter may look different, but it will perform the same functionRacorNew

Here is a fresh, new filter element for a popular primary fuel filter. It has nice, clean pleats on the filter paper. It only has to be immersed in fuel for a short time for it to discolor, but that doesn’t mean it’s in need of replacement.

Here’s a beauty! You can not make out the pleats for all the slime on it. Looking at this filter, we would recommend changing this filter a little more often.RacorClogged

Although this filter doesn’t have the external mess like the one above, it is waisted in the middle. This is caused by the vacuum generated by the lift pump on the engine. This filter clogged and the vacuum was generated as the fuel pump tried to suck fuel through it.RacorClogged2.

Heat Exchangers

Heat exchangers are the equivelant of the radiator in your car. The difference is the radiator transfers heat to the air and a heat exchanger transfers heat to sea water. Most heat exchangers are made of tube bundles where the sea water travels through the tubes and the engine coolant travels around the tubes. Exchangers can suffer all the problems that your car’s radiator does, plus some additional ones. The two most important items in the periodic maintenance list for heat exchangers is to keep the sacrificial zinc in good shape and to change the engine’s coolant regularly.

The zinc is provided to reduce corrosion in the heat exchanger. It functions by corroding away, “sacrificing” itself for the good of the copper in the exchanger. The zincs may need replacing every year or as often as every two months, depending on the environment and how the boat is used. It is better to replace the zinc before it needs it, rather on letting it dissolve away all together. If the zinc dissolves too far, you will not be able to remove the zinc portion from the threaded pipe plug. This isn’t a big deal, but it just adds a little cost. Also, if the zinc wears away unevenly, it can corrode at the base, letting the rest of the zinc fall into the heat exchanger. Not all exchangers have a sacrificial zinc as they are made of cupranickel alloy and don’t require the protection.

The coolant in your engine has a designed life expectancy. For “standard” ethylene glycol, it is two years and for “long life” propylene glycol antifreeze it’s five years. These are “projected” lifetimes and depending on the engine/service may too long between replacement. We use the term coolant because “antifreeze” is much more than it’s name. It has components that stop corrosion, lubricate pumps, and increase the boiling point of the coolant. Once the corrosion inhibitors get tired, then the coolant will begin to corrode parts of the cooling system, starting with the least noble metals, like aluminum. The seal in the water pump can fail if not lubricated properly. Coolant often contains “silicates” that can collect in the heat exchanger as it gets older, clogging it.

One of the most common problems is clogging of the sea water side of the exchanger due to foreign debris. The type of debris can vary from seaweed, to sand, to zebra mussels. Almost all heat exchangers have access plates that can be removed to clean out the debris. There are also calcium deposits that over time can block off the tubes or coat the tubes reducing the heat transfer. Acids can be used to remove the deposits, but it can eat through the tubes as well. Be sure to pressure test the exchanger after cleaning with acid. If you have replaced the sea water pump impeller and it had lost some of it’s blades, then most likely they have traveled through the hose to the heat exchanger. The pieces can lodge against the tubes and reduce the water flow.

Propellers versus Engines

When it comes to propellers there is quite a bit of mystery regarding which propeller is best for a particular engine and vessel. Although there are no sure fire answers, there are some guidelines. The proper propeller is instrumental in getting the maximum performance from your engine, regardless whether yours is gas or diesel, sail or power.

Each engine has a specific rpm where its maximum power is developed. The amount of power developed is a combination of rpm and torque. The faster the engine spins, the more power pulses are made and the more fuel is burned. Hence, the faster the engine turns the more power is developed. If the engine turns faster than it’s governor set for, then the governor will reduce the amount of fuel delivered and reduce the torque, reducing the fuel being burned . Inversely, if the propeller keeps the rpms below rated rpm, the lower rpm reduces the amount of fuel burned and therefore horsepower. A propeller that causes the engine to turn too fast or too slow will reduce the available power.

To determine what the proper rpm is for you particular engine, you need to consult your operator’s manual and look for it’s maximum rated power rpm. This is the rpm your engine should develop when underway in calm water. Some specifications provide “intermittent” power and “continuous” power. The intermittent rpm is the maximum power and is what the propeller should be sized for. Continuous power is the rating that you can cruise the engine at all day long. Take your boat out and get the engine warmed up. Open the throttle slowly until wide open throttle is achieved. With the boat operating at maximum speed, what is your maximum rpm? Is it less, or more, than the “intermittent” rpm in the manual?

Now comes the fun part. What to do with your prop? We’ll give you the simplified version by saying: Rpms are low, reduce pitch: Rpms are high, increase pitch. This is a huge simplification, but that is the basic idea. Most sail boats with a 2:1 transmission will respond by a change of approx. 300rpm for each inch of pitch change on the prop. Power boats can change more or less depending on type of boat, propeller, and gear.

Many owners are apprehensive about running their engines at wide open throttle as they don’t want to damage their engines. Running at rated rpm and throttle should be part of your diesel ( or gas) engines operating procedure. Not for extended periods of time, but just enough to make sure that your engine can still maintain full rpm. Conditions change, fuel load, people and gear load, fouling on the bottom and propellers, all contribute to slowing the boat (and engine) down. If your engine can only achieve 200 rpms less than it used to, then you need to reduce your cruising rpm as well. Otherwise, you will be operating the engine at a higher percentage output than you think.

So you have a new engine?

CONGRATULATIONS!! You have a brand new engine and it purrrrs like a kitten and it’s all shiny and bright. Here are a few pointers that come from frequently asked questions by new engine owners after we install it.

1. What is the break-in period and how do I run the engine? We normally consider 50 hrs. to be the “break-in period” on most engines. The engine really continues to “wear in” long after that, but as far as the owner/operator is concerned, 50 hrs. is it. During this time, we recommend that you avoid running the engine at high outputs for extended periods of time. If you want to give the engine a brief WOT (wide open throttle) for less than a minute, fine. It’s actually recommended to do that at least once each time the boat is used. This way you can make sure the engine will develop full speed and you can determine if anything has changed since the last time you used it. We like to have our customers “mix up” the rpms during the break-in period. This means don’t run the engine at one speed for the whole day. Every hour or so, change the engine speed, as much as practical. This changes the load on the engine and allows more complete break-in.

The first engine service, usually at 50hrs or so, is probably the most important service that your engine will have. This is where the oil and filters is changed which gets rid of all the particles of metal from the engine “wearing in”. In addition, you get remove any dirt or contaminants that might have been in the engine from the factory. Just like people under going an operation, engines get contaminated the worst from being taken apart and/or being put together.

At this point we also want to set the valve lash. Since the pushrods, rocker arms, and valves have all gotten to know each other better, they are not usually at the same setting as when they left the factory. Once we set the valves at 50 hrs., you can usually go for a couple of hundred hrs. before doing it again, but that will vary with each engine. If your 50 hr. check calls for re-torqueing the cylinder head bolts, then a valve adjustment is mandatory.

Engine alignment should also be checked at this point. The internal engine parts are not the only things that have gotten to know their neighbors better. The engine and the boat itself have figured out where they are going to be and that may not be the best thing for the propeller shaft. Engine mounts will tend to “settle” with vibration and pressure, finding where they want to be. They may allow the engine to fall lower in the boat, bringing the prop shaft out of alignment. As with the valve adjustment, once you align the engine now, you will not have to do it for several hundred hours.

Have you hugged your engine mounts today?

Most engine mounts are taken for granted and as long as the engine doesn’t fall off the beds, most people think everything is fine. Mounts and their systems are as important as anything else in the drive system. These devices have to hold the engine secure while isolating vibration from the boat. They have to allow the engine some amount of movement but still maintain the alignment to the prop shaft. Most mount systems have some type of “cushion” system, usually employing either rubber or springs of some kind. Springs can “work harden” over time and break, while the rubber (or “elastomer” can deteriorate through oxidation or chemical degradation. Fuel or lube oil leaking onto an engine mount will swell and soften the cushion material causing it to fail. The pictures below show just that type of failure. If the rubber looks “swollen”, it may have been exposed to petroleum products. Compare the mounts with each other. It is unlikely that all the mounts would have been contaminated equally. Be sure to find the cause of the contamination before you install new mounts.

Over time, the threads and nuts on an adjustable engine mount can corrode and become inoperative when it comes to adjusting the alignment. Most alignments don’t take that long, between 1-2 hours. If the engine is out of alignment, beyond what the mounts can compensate for, it may take much more time to get the alignment right as we may have to move the engine around quite a bit. Corroded adjustment nuts are the most likely cause of excessive alignment times, so every so often, apply some type of corrosion inhibitor to the nuts and threads of the mount. It will save you money in the long run.

Big Alternators

Many boat owners consider adding alternator capacity, along with additional battery banks. These often are to power inverters or to just prolong time between charging cycles. When installing larger alternators they’re are many things to consider. Here are some suggestions:

1. What are the specific goals of the improvements to your electrical system?
Many start down the road without a clear idea of where they are going. Determine your loads, load time, and desired charge time and you can figure out just what you need. If you are not familiar with this, email us or give us a call and we can help.

2. How big is your engine?
Smaller engines may have limitations regarding how much power (torque) can be extracted from the forward pulley. Small one and two cylinder engines have limited power available to drive larger alternators. Let’s face it, if your current engine is barely able to move your vessel at the desired speed now, what will it be like when your “big” alternator is working at 100% capacity?

3. How big is the V belt on the engine driving the alternator and how much contact does the pulley have with the belt?
Larger V belts can transmit more power than smaller ones, but it is a little more complicated than that. How many degrees of contact does the belt have with the alternator pulley also affects how much power can be transmitted. Most engines have approximately 90 to 120 degrees of contact, with the belt driving a fresh water pump and the alternator. The V belt on some engines only drives the alternator and that means 180 degrees of contact which is ideal. The less contact, the less power can be transmitted which translates into increasing the number of belts.
The easiest way to increase the amount of power available for an alternator is to double up on the belts. The picture above shows an alternator with a double groove pulley, one for each belt. We recommend that two belts be used on all alternators above 750watts (12volts, 60amps) whenever possible.
Now just because the alternator you installed is working just fine with only one belt, it may not always be that way. Day sailing around the sound, without anchoring out will not discharge the batteries enough to bring the alternator to full output. We have installed large alternators on vessels where there was no additional pulley available and they work fine all along the ICW. When the captain takes the sailboat offshore is when the trouble starts. The second day when the crew goes to charge batteries, the single v belt smokes off the pulleys!!

4. How hot is your engine room?
Another thing to consider is the amount of ventilation that is available to the alternator. Everything on the engine is liquid cooled in one way for another. The alternator is the only thing that is air cooled. The more power being generated by the alternator, the more heat it must get rid of. If the alternator is called upon to produce maximum power at lower rpms, or the ambient air temperature is to high, the unit can overheat causing diode and bearing failures. Make sure that the engine compartment gets enough cool air when charging the batteries. Remember that cooling air is drawn through the alternator from the back of the unit through to the fan in the front. Any ducts that are installed to provide cool air should be directed at the aft end of the alternator

5. Mounting the alternator.
How the alternator is attached to the engine is very important as the higher output units can put considerable loads on the brackets. First, the pulleys must be aligned. You can use a straight edge to place against the front face of the pulleys to check the alignment. You may have to move the alternator forward or backward to bring the pulleys into alignment. Make sure that the pivot foot of the alternator has no lost motion or play in the mounting bolt. If there is any looseness in the foot of the alternator, the vibration will wear the ears of the alternator or the engine housing.

6. Regulators
Regulators control the alternator’s output according to the electrical systems needs. It does this by monitoring the voltage of the DC system. When the voltage drops, it increases the field current, increasing the output of the alternator. If the voltage rises above the set point it reduces the field current, reducing the output. As the speed of the alternator increases, it’s output increases, so to maintain the same output, the field current must be decreased as the rpm increases.

Regulators come in many different kinds. Some are integral, meaning that they are part of the alternator, either bolted in the back or actually inside the alternator. Others are remote, meaning that they are only attached to the alternator by wires and the regulator itself is mounted away from the alternator.

Additionally, regulators do not all function the same. Some are what we call “dumb” regulators, which only control the voltage of the system. Some regulators have small “computers” in them that adjust the charge rate according to time, type of batteries, or battery temperature. They may be called three step or smart regulators. More sophisticated regulators can increase your battery life and decrease the battery charge time. One of the most important aspects of regulators is the type of batteries they are designed to charge. Lead acid batteries, AGM’s, and gelcells all require different charge rates and maximum voltages. Do not mix the type of batteries in your boats system as if they are not uniform, they will not be charged properly.

7. Alternator wiring

Make sure that the wiring for this new alternator is of the proper size. Most engines are equipped with a 55-70amp alternator from the factory. The wiring will be sized for that amount of current. Once you go to 120amp alternator, you should have 2ga. cable connecting it to the boats DC system. If the engine harness utilizes a ammeter at the helm station, it will have to be removed from the system. The distance from the alternator to the batteries should be as short as possible to reduce voltage loss.

Do not forget the ground cable when you are wiring your alternator. Just because the case of the alternator is grounded to the engine, it doesn’t mean that the ground path is able to handle the higher current. Install a 2ga. cable from the case (or ground terminal) of the alternator directly to the ground buss of the boat. This will eliminate any voltage drop through the engine block. Steel isn’t a very good conductor of electricity as compared to copper.