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Diesel Operation (1GM10)

The way you start a 1GM10 is to turn the key on and push the starter button. This assumes the raw water seacock is open and the battery switch is on. Of course we noted that the warning lights worked and the warning noise from the control panel was audible. After the engine starts, we check to see that we have water coming out the exhaust port. We need to hear the putt, putt, putt and then a splash. I also like to check the amount of water coming out the exhaust port. Less water than usual and the pump impellor could have problems. If it is cold weather, we may need to move the throttle forward to increase speed to maintain an idle speed after the engine starts. This will not be necessary during the summer months or after using the engine. Your idle speed is going to be around 1000 rpm. When you put the engine in gear, the speed will drop a little and you donít want to kill the engine. The best idle speed is the lowest speed that keeps the engine running when you put it in gear.

Most engines have 2 sweet spots in their rpm range. I call them low and high cruise engine speeds. I pick the one I need for the purpose at hand. If I have 14 hours of motoring to do and I need to get somewhere during daylight, high cruise would be my choice. If Iím out for a Sunday sail, low cruise normally works just fine. The sweet spots that Iím talking about are really smooth spots. It happens when the engine and everything on the boat vibrates less.

Changing engine oil and filter once a year is a good practice. Having anti-freeze inside the water passages of a stored engine is also a good practice. A valve adjustment every 2 or 3 years might be a good idea. Staying away from sandbars with the engine running is another good idea. The little engine is good at packing sand in the cooling cambers of the block. If the engine doesnít use oil, just check the oil every now and then.

Carbon buildup in the engine should be avoided. The best way to do this is by not running the engine at idle speed for long periods of time. The engine is at its most efficient condition when it is running at cruise speed under load. Burning all the fuel in the engine will reduce carbon buildup. When you shut the engine down, bring the engine to idle and let it run for about a minute to cool down before you shut it down. The ignition switch canít stop the engine and turning it off while the engine is running may damage the alternator. Also, never turn the battery switch off while the engine is running. This disconnects the battery from the alternator and the alternator diodes could be damaged. Shut the engine down by pulling the fuel shut off cable.

Owners need the factory manual that comes with the engine. It gives you lots of important details that you will need from time to time.

All inboard diesel boats need an automatic bilge pump that works. Water is the lubricate for stuffing boxes and a stuffing box is designed to keep the water out of the boat. The stuffing in a stuffing box lasts for a long time. Most stuffing boxes are located at water level on most sailboats. The shaft brings the water up to the stuffing box as the shaft turns. This water is still present in the log after we shut the engine down for the day. If you look at the stuffing box after a day of motoring, it will be dripping. Dripping doesnít mean very much at this time. After you get off the boat and then when you come back the following day, the water in the log will be at a lower point in the log. This is your reference point for stuffing box leakage. It may be dry or just leaking a small amount now and then. Putting the stuffing box at the water line is a smart thing to do when you design a sailboat. You can see that if the stuffing box was located 3 feet below the water line, stopping the drips could be a big problem. Some people load their stern lockers with lots of heavy stuff. That could cause stuffing box leakage problems. In any case, when you have a stuffing box, you need a bilge pump that works in automatic mode. Most stuffing boxes donít fail or leak to excess, but a good bilge pump to watch over your boat while you are away is important.

Advanced Operational Details:

If the 1GM10 didnít have a governor, it wouldnít be much as an engine. Diesel engines respond to changes in load and thatís what makes these little engines work so well. Most outboard motors find their power with engine speed. The little diesel engines run much slower and they get great mileage and sufficient power when they use their governor. The governor on the IGM10 is revolving weights that move with the crankshaft. When the waves get bigger and the boat slows, the propeller slows, the crankshaft slows, and the revolving weights slow and the governor add more fuel to engine to maintain the speed that we programmed before the waves arrived. I have operated a 1GM10 without an operational governor and it doesnít work very well. The engine runs, but it takes a long time to reach a set speed using the hand throttle. A diesel without a governor is a very weak machine.

The 1GM10 and most diesel engines are mounted at 5 points. These 5 points are very important for smooth engine operation. The 4 points that most people think about first are the engine mounts. The other point thatís just as important is the cutlass bearing in the shaft log. These five points support the engine in the boat. If they are correctly aligned and in good condition, engine operation should be smooth. A good trick is to look at the cutlass bearing from the outside the boat. Is the shaft sitting in the middle of the bearing? Is the bearing worn on one side? A shaft sitting in the middle indicates good alignment and a bearing worn on one side indicates the engine needs alignment and a new cutlass bearing.

Engines are made to be used with specific propellers. The boat itself doesnít make much of a difference in which propeller is used. However, the right engine for a specific boat is important. If you bolt your engine to a dock and run the engine with the shaft and propeller in the water, whatís going to happen? The engine would increase in speed as you increased the throttle. You would get to a point where the engine would start to put out black smoke from the exhaust indicating that all the fuel was not being burned in the engine. This is as fast as this engine will run with this propeller. Of course it goes without saying that you shouldnít run the engine faster than its recommended maximum speed. If you had a very small prop on the shaft, the engine would run too fast too soon and the engine would get to maximum speed before you saw black smoke. If you had a very big prop on the shaft, the engine speed would go up in speed until the engine started to put out black smoke indicating all the fuel is not being burned. The best prop for most boats is a prop that puts out black smoke just before reaching maximum engine speed. This may be more than most people want to know about diesel engines.

Everyone thinks putting a 3 bladed propeller on his or her boat might help performance. Maybe they can get more power and speed with the extra blade? The extra blade reduces cavitation between the blades and makes engine operation smoother. It does not increase power or speed. The power from the extra blade is cancelled from its associated drag.

Using a small diesel as auxiliary power in a small sailboat is about as good as it gets. Take care of them and they will take you just about anywhere.

Fuel System

The fuel storage location on a CP23D is in the cockpit. The boat was designed to use an OMC 6 gallon gasoline tank with outboard motors. The OMC tank was made of steel and didnít last very long in the marine environment. The original tank was modified with a return line when it was used on a 23D. OMC went out of business and the metal tanks became history. Most 23D tanks today are custom plastic tanks with 2 connections for supply and return. The supply hose uses the standard outboard supply port and the return is a little more complicated. We remove the fuel level gage from the tank and install hardware for a second supply port. The downspout on the return is not needed. The hole size and threads are the same for the supply port and the fuel level gage. Itís a jury rig system that works well.

The tank isnít portable in its diesel application. The 2 hoses connected to the tank are installed with hose clamps and the system might need bleeding if they are removed. We normally add fuel to the tank with another container that we keep somewhere else. You can get fuel at a fuel dock, but the tank doesnít hold very much. Thatís really a good thing because we donít want our fuel to get old and grow fungus. We normally use a wood stick to measure the fuel level in the tank.

Starting with the supply line at the tank, we have a hose that runs to an electric fuel pump. This pump is used for bleeding the system and is operated by a switch on a panel above the steps. Some boats use a squeeze bulb. Once the bleeding has been completed, the pump is no longer needed. Gravity will supply the engine with fuel. The next stop after the pump is a 30-micron fuel filter. This filter is called a secondary filter because the primary filter is a Yanmar filter on the engine. The next stop on our fuel journey is the mechanical fuel pump on the engine. It can be pumped by hand if required. No need if the electrical fuel pump is working. The fuel runs from the fuel pump to the engine fuel filter, then to the injector pump and on to the injector itself. Most of the bleeding will be done at the injector in front of the engine. From the injector, a return line for the unused fuel returns to the tank.

Bleeding the system is a good trouble-shooting procedure. Diesel engines only require fuel and air to run. Turn on the electric fuel pump and back off the bleed screw at the injector and you should have a stream of fuel with no bubbles. I use a paper towel to catch the fuel as it comes out the bleed hole. Keeping a 10 mm wrench handy for that purpose is useful. Once the bubbles have disappeared, close the bleed valve and turn the electric pump off. The engine should start and run normally. Cold weather may require a small amount of throttle. The 1GM10 normally starts in neutral with no additional throttle. If the engine starts and runs below 800 rpm and dies, give it a little throttle. It really better to start without the extra throttle and give it more throttle once it starts to keep it running. This procedure is for cold outside temperatures only. Normal 70 degree-days do not require special procedures. A warm up is required before you put the engine in gear and leave the slip.

Normal idle speed is 1000 rpm. All shifting should be done at idle speed. No special maintenance procedures are required for the fuel system. Old fuel is the biggest problem with the fuel system. Fuel additives for the fuel system for hot climates are a desirable practice. It best to have a set of filters on hand and know to change them. You become an expert after the first filter change.

The picture above shows the bleed port at the front of the engine. Just follow the hoses to find the next component in the system. Changing the fuel filters once a year is a good practice for the fuel system. Some owners never change the primary filter and only change the secondary filter when they have a problem.

A fuel malfunction is normally an engine that runs slower on itís own. The fuel control determines the amount of fuel going to the engine. A clogged fuel filter slows the amount of fuel going to the engine and the engine slows down on its own. An emergency solution for this problem is to run the engine slower until you can service the filter. Itís normally the secondary filter that gets contaminated first. The secondary filter is the first filter in the circuit. It may be a 30-micron filter. The primary filter thatís mounted on the engine might be a 10-micron filter. The idea is to stop the big stuff before it gets to the engine and the primary filter.

When you change fuel filters, replace the filter element and then fill the filter container with fresh fuel. This will reduce the amount of air in the system and reduce the amount of bleeding.

Cooling System

The Yanmar 1GM10 is a raw water-cooled engine. . The exhaust discharge at the transom contains the water that was used for engine cooling. When the amount water leaving the transom is reduced at startup or when the temperature warning sounds, look for a bad water pump impellor or an obstruction in the cooling system. Persistent cooling system problems may indicate contamination. If the engine is used in salt water, an acid cleaning of the cooling system is necessary every 5 to 10 years. This opens up the block and removes the contamination.

The system construction starts with a through hull port accessed using the portside seat locker. A seacock is next and a raw water strainer after that. Itís common to have trouble with the strainer lid not fitting well enough to prevent air leaks. Close the lid and check for leaks if the engine pump doesnít pump water. A boat passing in front of you in a channel may be cutting grass (weeds) as it moves down a shallow channel. These bits of grass will collect in the strainer. Enough grass and the water will stop flowing in the cooling system. The high temperate light will light and the warning buzzer will sound if you donít have water. You stop the engine after checking to make sure there isnít any water coming out the transom. No water indicates a hot engine and a cooling water problem. Removing the lid from the strainer may show long blades of grass in the strainer and in the hose leading to the strainer. You remove the grass, replace the lid and you can be on your way. This happens to all types of motors including outboards in shallow channels or after a big storm.

A spare impellor and a small amount of grease should be kept on board. When you start your diesel engine and it is warming up, the exhaust and the water coming out the exhaust will make a special noise. I like to think of it as putt, putt, putt and splash and then the same thing over and over again. If you hear more putts and not enough splashes, you may be losing some of the vanes in the pump. Most impellors are good for 2 years of recreational use. A good impellor sound will become second nature. If you use your boat enough, your pump sound at idle will tell you when you need a new impellor. You install the new impellor with a little grease on the blades to make sure they are wet at startup. A new impellor today comes with lubricate in the box.

If you use your engine to get off the bottom in sandy conditions, you will pack the internal engine passages with sand. Using an anchor to get off the bottom is better for the engine. Following a boat that dragging its keel on the bottom will produces he same results.

The warning light for high temperature engine isnít checked when you turn the key on. The sensor for temperature is off when it cool and closed when it too hot. What appears to make the lights work is an oil pressure-sending switch. When the engine is stopped, we have no oil pressure and that causes the oil pressure light to light. When we have oil pressure, the oil pressure switch opens causing the oil pressure light go off. A voltage light for the alternator works about the same way. The temperature switch is the dumb switch that only works when the engine gets too hot.

Engines that use salt water as a cooling source likes to be stored with anti-freeze in the cooling system. Anti-freeze is a rust inhibitor and will prevent one of the common failures with the IGM10. The water/exhaust mixing components in the exhaust manifold can corrode and fail over time. Storage with anti-freeze in the cooling system will reduce manifold replacement to a minimum. Most engines have a separate anti-freeze hose for this purpose. Close the water inlet seacock and open the value used for flushing. Drop the anti-freeze hose into a gallon container of anti-freeze. Start the engine and run the engine at idle. When you see anti-freeze coming out the exhaust port, stop the engine. The engine is now protected from freezing and corrosion.

The engine has a water drain located on the starboard side of the block. It has a knob that can be turned with your hand. You may need pliers. The drain has a hose connected to it thatís pointed towards the bilge. Draining the fluid from the engine will prevent freezing.

Both methods of winter storage are acceptable. The anti-freeze method is better when the boat is used in salt water.

Lubrication System

The 1GM10 engine uses multi-grade oil for lubrication. 10W-30 is suitable oil for use on East Coast of the United States. Buying oil designed for diesel engine is desirable if possible. Changing oil is done with a warm engine. I like the vacuum drum oil changer sold by West Marine. Itís inexpensive and works well. Remove the old oil from the engine and then remove the filter. Having an oil filter-removing tool in your tool kit is a good accessory. Replace the oil filter and then fill the engine with a quart and a half of oil. You will need to add more oil after you run the engine. The engine takes a little less than 2 quarts of oil. You donít want to overfill the engine and the filter needs to be full of oil for a good measurement. Run the engine let the oil settle and then measure the oil level. I like it to be half way between the full mark and the low mark. I always check the oil in the engine when the engine is cold. Where you maintain your oil level between the marks on the dipstick is up to you.

Oil or fuel leakage is a reason for repair. A leak needs to be identified and stopped. The motor mounts on the 1GM10 can be destroyed by fuel or oil leakage. The rubber in the motor mounts will fall apart if fluid from the engine makes contact over a relatively short period of time.

Most automobile parts store will have a cross-reference chart for oil filters. Filter prices at the parts store or on-line are substantially lower. Engine oil should be changed once a year for most recreational sailors. I sometimes go longer if the boat and engine are in storage and they havenít been used. Oil in the can is a little like oil in an engine thatís not being used. Oil in a can doesnít have a shelf life.

The oil warning light is the smart light. It works off pressure. No pressure and the light is on because the oil pressure switch is closed providing a ground for the light to light. As soon as you generate oil pressure, the switch contacts are broker and the light goes off telling you that you have oil pressure. The alternator light works almost the same way. You turn on the ignition switch and the warning lights light telling you that they are working. The alternator has 12 volts on one side of the light and a ground on the other in the alternator when it is not moving. When the alternator turns fast enough, the previous ground in the alternator becomes more than 12 volts (maybe 14 volts). The difference in voltage between the two sides of the bulb isnít enough the light the bulb and light goes off. It works the same in your car. We can call the alternator warning light almost as smart as the oil light. The temperature warning light is connected to a switch that only works when the engine gets hot. It doesnít light for test purposes when you turn the ignition switch on. Itís the dumb light and it may not work because its function is never tested.

The 1GM10 transmission uses the same oil as the engine. This makes life better with fewer containers to deal with. One of the great mysteries of the 1GM10 is the transmission oil measuring method. The book calls for an oil level between the upper and lower marks. There may be transmissions on some engine somewhere in the World that have upper and lower marks. I have never seen one. Our dipsticks have an upper mark and thatís it. On transmissions with only one mark, we measure the oil level between the mark and the bottom of the dipstick.

It is easy to overfill both the engine and the transmission. If you overfill, you need to remove the excess oil before operation. Running the engine without the dipstick in the dipstick hole will cause oil to spill out the hole and make a mess. Never start the engine without the dipstick in place.

Some users check their engine oil every time they use their engine. Some never check their oil. If you determine that your engine doesnít burn oil or leak oil, then I would only check the oil with the dipstick on a random basis. Not burning or leaking oil is a standard condition for a 1GM10 engine.

The Sailboat Company
Richlands, NC 910-324-4005