The First Ten Seconds

29 07 2008

F.V. Atlantico

F.V. Atlantico

If we could look inside a marine engine and watch what’s happening during the first ten seconds of a cold start, we might be surprised!

Over the life of an engine, eighty percent of the wear to engine bearings will take place as the engine begins to turn without lubrication, during cold starting.

When an engine is turned off, the lubricating oil slowly leaks from between the components that depend on the oil film and its wedge-effect. The oil wedge-effect is present when engine components are separated by lubricating oil, and there is sliding or rotational movement. However, when oil pressure ceases and the engine sits still for a little while, large pockets of air enter the lubrication system. This air must be eliminated by oil pressure once the engine starts. As the engine begins to turn, the oil pump quickly lifts a column of oil from the oil pan and goes about forcing all the air from the lubrication system.

When a 12-volt starter motor begins cranking a cold diesel engine-in the 300 horsepower range, voltage at the starter can drop from 13.8 volts to only 11. Amperage can go from zero to well over 1000 amps in an instant. The affects of the sudden electro-magnetic field around the starter cables may make them jump or seem to “crawl”.

The fuel system quickly begins to build high pressure for injection into the cylinders. The injectors begin forcing fuel into each cylinder; one at a time, in the engine’s firing order. Smoothly carried forward by heavy flywheel that keeps the crankshaft rolling on to the next cylinder in the firing order, and the next and the next…

Many mechanical governors go into the full fuel mode when the engine is off. This happens so the injectors will have a real “kick” for starting the engine. These same engines, equipped with a mechanical variable timing unit will also keep the engine injection timing fully retarded to aid starting. When the engine starts turning, each injector will be putting in near their full volume capability until the engine speed gets up to the governor’s pre-set low idle speed. At which point, the governor will quickly feather back the fuel delivery to maintain a steady low idle speed.

When the oil pressure comes, the crankshaft and the flywheel quickly rise to the center of their bores in the cylinder block and flywheel housing, both lifted and supported by the oil wedge. The oil wedge acts between the crankshaft journals and the engine bearings. It would not be far-fetched to say the crankshaft is “surfing” on a film of oil, at this point.

If the crankshaft main bearings have five thousands (.005”) of an inch oil clearance, then the presence of lube oil lifts the crankshaft and related components nearly half this distance, or approximately .0025”of an inch, to the center of their bore. This weight can be the several hundred pounds of steel and cast iron that the crank and flywheel consist of. If the engine has a front mounted power-take-off clutch, the oil film must lift this additional weight as well. On larger engines this total weight can exceed a thousand pounds.

The cold and dense column of air in the exhaust system begins to move, slowly at first, like molasses, as the engine turns and starts. The 400 degree F gases that are clamoring to work their way out from below have a much easier time flowing in, around and through the exhaust system. As the exhaust gases warm they expand, losing density, becoming much easier to pump up the stack.

The oil pump for the marine gear turns any time the engine crankshaft turns. Therefore, as the engine begins to fire, it must overcome the increasing power demand from driving all the so-called parasitic loads.

Parasitic loads are those loads (or work) that must happen in order for the engine and marine gear to run properly.

Suddenly, there is a demand for fresh air in the engine room, and lots of it, as all cylinders begin to fire!

We’ll let it warm up, and then it’s time to go fishing…

(Some of this material excerpted from “PRACTICAL BOAT MECHANICS”, by Ben L. Evridge, to be published this fall.)

F.V. Ocean Bay

F.V. Ocean Bay





Flywheel Housing Leaks On Generator Sets

25 07 2008

Fylwheel Housing Oil Leaks On Generator Sets

Fylwheel Housing Oil Leaks On Generator Sets

One of the more important maintenance items to watch with generator sets is the engine’s rear crankshaft seal. When the seal fails, engine oil leaks into the flywheel housing between the generator windings and the engine. A quick inspection of the air discharge end of the generator can tell if there is a build up of oil and dust. Oil visible in the flywheel housing should serve as a red flag signaling the need for maintenance.

The general drawing to the left here shows possible sources of oil leaks in the flywheel housing, however, most newer engines do not have wet bolt holes in the crankshaft or flywheel housing bolt holes.

Inside the flywheel housing are three things: 1-The drive plates that couple the generator shaft to the flywheel, 2-The engine’s flywheel, and 3-The engine’s rear crankshaft seal.

Generator engines normally turn at either 1,800 RPM or 1,200 RPM. Therefore, any oil that leaks past the rear seal is flung outward by the spinning action of the flywheel. The oil is then picked up by the air coming from the generator fan and becomes an airborne mist. This oily mist is carried throughout the generator enclosure because of the tremendous amount of cooling air that the generator fan moves through the generator. Many generator sets move between 500 and 1,200 cubic feet of cooling air per minute (CFM). This means that, in a small engine room, several times the volume of air in the enclosure can pass through the generator every minute.

Unfortunately, the oily mist re-circulates back to the air intake portion of the generator and is pulled through the generator again and again. This puts a uniform coat of oil on every part of the generator. The oily mist is also pulled into the generator engine’s air filter. In fact, any engines running nearby will draw oil into their air filters causing premature airflow restriction.

Oil on the generator windings acts as an insulator, slowing heat transfer. This will prevent the windings from being adequately cooled.

Speaking of generator winding insulation, other related problems occur when there is the least amount of water or salt spray coming into the generator air-stream. Even splash from bilge water, on board a boat, in rough weather can find its way into the air stream that is passing through the generator end. The problem here is that water contains minerals that will carry electrical current and can cause a short circuit if a crack develops in the winding’s insulation. Bilge water also carries microorganisms that eat the insulation from the windings in the generator.

In fact, generator winding insulation is degraded when anything other than cool dry air passes through the generator including dust, oil, fresh water, or saltwater.

At the first hint of a seeping rear seal, it’s time to find out if the seal has failed, or there is some other problem.

As you begin to troubleshoot the oil leak, first check the engine oil level to learn if the level is too high. A high oil level can cause even a good seal to leak. Someone may have filled the engine with too much oil. Or, perhaps the engine may be mounted at an extreme angle. It is also possible that you may need to check the dipstick calibration. Each engine maker has a suggested method for calibrating the dipstick. Refer to your engine manual.

Fuel or coolant leaking into the engine’s oil pan can explain a high oil level in the engine. Yet another cause of a rear seal leak is a restricted crankcase vent line. When pressure in the crankcase gets above two pounds per square inch (PSI) the rear crankshaft seal will usually fail.

Engines that have wet bolt holes in the flywheel-mounting flange can experience a leak through one or more bolt holes, too. Some engines also have wet bolt holes in the flywheel housing that can mimic a rear seal failure.

Note: A wet bolt hole is one that allows the bolt to thread into part of the engine that contains engine crankcase oil.

One more reason for rear seal failure occurs when an engine has many hours of service and the rear main bearing has worn excessively. In this case the crankshaft can wobble as it turns while the engine is being started. This wobble will cause the rear seal to leak. The rear main crankshaft bearing will often wear more than the front engine bearings because the engine must start dry with the weight of the generator’s revolving member hanging on the flywheel.

(Some of this material excerpted from “PRACTICAL BOAT MECHANICS”, by Ben L. Evridge, to be published this fall.)

Crank Main Bearings Wear More At The Flywheel End

Crank Main Bearings Wear





Plug That Critical Passage!

22 07 2008

Plug Critical Passages

Plug Critical Passages

When working around critical passages and scraping gaskets, be sure to plug the opening, as shown here. Next, scrape the gasket, taking care to work around the shop cloth. This practice will protect the engine from contamination.

Scraping The Gasket

Scraping The Gasket

Unplug The Passage When Finished

Unplug The Passage When Finished

(Some of this material excerpted from “PRACTICAL BOAT MECHANICS”, by Ben L. Evridge, to be published this fall.)





Four Important Ratios

22 07 2008

Ratio Of Steering Cylinder Travel To Rudder Arm

Ratio Of Steering Cylinder Travel To Rudder Arm

Remember these important ratios that make or break your boat’s handling.

1-Ratio Of Steering Cylinder-To Rudder Arm Travel: When steering components are changed or a new boat is built, the steering helm can require too many turns to steer the rudder from lock-to-lock to be practical. This will also greatly reduce the steering effort. Or, if the system has insufficient turns, the effort required at the helm can be far too high to be practical.

To remedy these conditions, move the point of connection to the rudder arm out if the effort is too high. If on the other hand the system requires too many turns, move the point of connection inward toward the rudder shaft, even drilling an additional hole if needed.

Ratio Of Engine Speed-To Transmission Output Shaft Speed

Ratio Of Engine Speed-To Transmission Output Shaft Speed

2-Ratio Of Transmission Output Speed-To Engine Speed: When a diesel engine turns at 2,000 rpm and the propeller shaft turns at only 1,000 rpm, it is said that the drive ratio through the transmission of 2:1. Put another way, 2,000 rpm is going into the front of the transmission but only 1,000 rpm comes out the back. This is accomplished by using two gears inside the transmission running together. From the ratio we can see that the driving gear, the one from the engine, must have half the number of teeth than those on the gear that drives the propeller shaft. The gear reduction is what allows the engine, transmission, and propeller shaft to work together to move the boat efficiently through the water.
3-Ratio Of Governor Lever-To Throttle Control Movement: The response of engine speed acceleration can be changed by altering the ratio of the control-to the throttle lever movement, as shown.

4-Ratio Of Transmission Shift Valve-To Travel Of Shift Control Movement: The same is true for the shifting mechanism.

Ratio Of Control Travel-To Engine And Transmission Levers

(Some of this material excerpted from “PRACTICAL BOAT MECHANICS”, by Ben L. Evridge, to be published this fall.)





Hammer Invented By Fisherman’s Frustrated Wife…

21 07 2008

No matter how high tech the world becomes, there is one basic piece of equipment on every fishing boat: The hammer.

My wife, Irene, assures me that the hammer was one of the earliest inventions, and that it was invented by a fisherman’s wife; a frustrated woman who really thought her husband should get a job up the hill at Igor’s arrow head factory. This same lady mentioned to her husband from time to time, that all of the other men in the camp worked for Igor, and that she would really enjoy the convenience of having the parched corn with which Igor paid his men.

Since his jaw had started hurting, her husband had been obsessing about this thing he was trying to invent, something he called a “wheel”?? The wheel was the basis for a so -called “cart” he envisioned, that would allow his family to make the move from the summer fish camp on the beach, up to the winter camp, in only two “suns”. It had always taken at least as many suns as he had fingers. After all, he wasn’t getting any younger. The cart would be a big help in the coming Fall, especially because he hadn’t felt well, with his jaw throbbing so.

Yes, the cart would be a big help, especially when bringing fish home from the fish wheel at night and would really help the quality of the winter’s fish supply. However, it sure was a sticky problem, figuring out how to form the stones he had collected, into the shape he wanted. Besides that, the fellas at the arrowhead factory had taken up ribbing him about what he was doing rolling the huge rocks up from the river.

He had to wait many suns to get an appointment with the new young Shaman to have his jaw checked. The Shaman had waved the jaw bone from a Saber Tooth Tiger over him and had determined that while it might feel like a toothache, it was actually just a case of “Phantom Tooth Syndrome”, and that it would pass in time. He found this comforting, and he left the Shaman’s office marveling at both the accuracy of the diagnosis and the price of the Cat Scan.

Arriving home after his appointment, his wife showed him that he could shape one of these “wheel things” from stone, by using something she’d been thinking of for some time, a thing she called a “hammer”. “The hammer is really just a stone with an attached handle.” she explained, “However, a hammer could strike much harder than a hand-held stone could, because the long handle would allow the stone to travel much faster than their old method of holding the stone in a hand and hitting things with it!”

All he needed to do was to use the hammer against the big stones he had gathered, and he could quickly shape the stones to make the wheels. While his original design called for the wheels to be square, with a round hole in the center, his good wife had also explained that her mother, who lived with them, wouldn’t prefer to ride on a bumpy cart down to the river to do laundry. “Why”, she asked, “didn’t he make the wheels round, like the cross-section of a log, for a smooth ride?” “Besides this”, she explained, “A round wheel would have only one-tenth the inertia of the square wheel.”

He explained, “The square wheel design would act as a built-in emergency brake when going down steep hills and would prevent the cart from getting ahead of the mastodon that was to pull the cart.” ” It would also prevent the cart’s leaving without the mastodon, on real steep hills!” He reminded her that his mastodon had no shortage of power and that the mastodon could easily overcome the high power requirement of the square wheels.

Yes, she knew the mastodon was very strong, like he was, but wouldn’t it be better to keep the mastodon grinding meal? Then, by avoiding steep grades and using round wheels the cart could be pulled by one of the stray dogs in the camp?

Won’t you just try this round style first?” she asked, and she then promised to get started on his favorite dish; boiled halibut smothered in marrow from deer bones…





Troubleshooting Low Power

18 07 2008

Troubleshooting Low Power Complaints

Troubleshooting Low Power Complaints

There are many mechanical or electrical things that can go wrong with any boat engine. Troubleshooting is the process of reducing the number of variables to a very small number of realistic possibilities that can affect the engine in question. The following list will help you find the problem.

Air Filter Obstruction-A plugged air filter will reduce power, and on boats a slight exhaust leak will quickly plug the filter. Just remove the filter and do a visual inspection by shining a light from the inside out. If you can’t see light through the filter it’s time for replacement.

Exhaust System Obstruction-A collapsed silencer or plugged exhaust system will lower power as well. Have your marine technician perform a back pressure test on the system to see if this is the case.

The Fuel Supply-The fuel supply system easy to forget. First of all, check your fuel level and make sure there is plenty of fuel in the tank. If there is no fuel-level gauge or the existing gauge is questionable, then you must dip the fuel tanks. And, while you are at it, apply a dab of water finding paste that is available from your fuel dock, on the end of the stick to check for water in the fuel. If your fuel level is satisfactory then move on to the fuel filters.

Check the fuel filters for the presence of water and to be sure fuel is flowing through the filter. If you have recently changed the filters, then check for air in the engine’s fuel pump and injector lines. This air may have entered the system during the filter change.

Another area to consider when power is low is fuel line sizing. Some older boats might have, for example, a one-half inch fuel pipe coming into the engine room. This line may have been enough to feed the original engines when the boat was built. However, over the years after the boat was re-powered and new generator sets were installed in the engine room, you may notice times when one or more of the engines seem to be sluggish. You may also notice that the lights brown-out when the main engine is also running because there isn’t enough fuel to supply engines. If so, it is time to upgrade the fuel supply line to what the factory specifies for each engine, plus a little extra. First calculate the cross section of the inner diameter of all fuel lines and then add them together. After getting the area of cross section needed to feed them all, go up to the next higher sized pipe to feed all of the engines adequately.

When upgrading fuel hoses, be sure to buy U.S. Coast Guard hose. See the following link:

http://www.yodio.com/yo.aspx?CardId=A7Jct5AjaL6EjjDvzGZtXJ

Inspect your fuel return lines as well. Some engines will not run well with a plugged or restricted fuel return line. Since most vessels have a valve on the return line, it is also important to check to see that the return line valve is definitely open.

A less common problem, but one that does happen, is accidentally filling up with No.1 fuel oil when you really need No. 2. This will reduce engine power because there is simply less energy in a gallon of No. 1 fuel than in a gallon of No. 2.

Controls-Verify that the governor speed control is getting full travel when you have the speed control in the full fuel position in the wheelhouse, or on the flying bridge. The transmission control needs full travel as well, and if you have a trolling valve, verify that it is closed when accelerating the boat.

Air in the Fuel-If you begin to bleed the air from the fuel system and the air just keeps coming, then it is time to use the sight glass.

A sight glass lets you spot air in the fuel. The place to install a sight glass is between the low-pressure fuel transfer (i.e., lift pump) and the high-pressure pump or unit injectors depending upon the type of injection system on the engine. Be sure to check the pressure that your transfer pump produces and be sure that your sight glass is rated for this pressure. Most major engine makers can supply a suitable sight glass through their parts sales organization.

If you can see even one bubble of air coming in with your fuel, then there is at least five percent air in your fuel. Air in the fuel will seriously limit the power the engine delivers and can cause hard starting as well.

When you do find air in the fuel, the next thing to do is to examine all fuel lines, hoses, fittings, and clamps between your engine and its fuel supply-on the suction side of the system. When air leaks into the fuel are repaired, you’ll feel the difference.

Electronically Controlled Engines-Verify that no trouble codes have been stored. If you see a code for a problem, contact your dealer and get a technician to plug in his laptop to find the problem.

Line In The Wheel-When nothing else is showing up as a problem, try this: With the engine stopped, take a hold of the propeller shaft with your hand and feel how hard it is to turn the shaft. Usually you can turn a shaft as large as 2″ inches in diameter by hand. If it’s hard to turn, get a diver to see what is wrapped around the shaft.

Further In-Depth Testing-When black smoke (mechanical engines) and hard starting are involved it is time to ask your technician to check the compression and fuel injection timing as well.

Questions and Comments-Please let us know your thoughts on this article and suggest new topics you would like to see.

(Some of this material excerpted from “PRACTICAL BOAT MECHANICS”, by Ben L. Evridge, to be published this fall.)

 





MERPOWER-Broken Fasteners

11 07 2008

Weld the washer to the stub before you weld the nut!

Weld the washer to the stub before you weld the nut!

1. Removing Broken steel engine exhaust bolts or studs that are broken off in a blind hole: If possible, start the engine and get it up to operating temperature, then turn it off immediately and disassemble as necessary to the point where penetrating oil or even candle wax can be dripped on the exposed threads of the exhaust bolt or on the bolt stub. The oil/wax will find its way along the bolt threads. If there is a stub sticking out, an effort must be made to grab it with Vise-Grip locking pliers. If it can’t be gripped, try to carefully turn it out of the hole with a hammer and chisel. A bolt remnant that has broken off flush or below the surface of the work piece will usually be loose in the threads. In such a case, it often works to carefully use a punch or chisel and drive on the outer perimeter of the bolt to turn it counterclockwise.

If these efforts fail then it is a good idea to first weld a washer onto the stub, and then weld a nut to the washer. Next, attempt to turn the stub out by the nut that was just welded.

If this won’t move it, use a left-handed drill bit to drill a hole in the bolt so that an Easy-Out may be driven into the freshly drilled hole to remove the bolt. Just starting to drill a broken stud with a left-handed bit will typically be enough to turn the bolt out of the threads.

A six-point wrench will grip a worn bolt head.

A six-point wrench will grip a worn bolt head.

2. …. a rounded-off bolt head or a head that has rusted away: First, try an undersized 6-point box-end wrench as shown. If this does not work, dress off the rounded head and press or drive a larger nut over the head of the bolt, then weld the larger nut to the bolt head.

 

 

Removing a through-bolted stub

Removing a through-bolted stub

3. …. a bolt used for through-bolting is broken-off: If the back of the bolt can be accessed, it can sometimes be turned by gripping with pliers after treating it with candle wax or penetrating oil.

Removing a below-flush stub.

Removing a below-flush stub.

4. …. a threaded bolt used for through-bolting is broken off, but not in a blind hole: A broken threaded bolt in this state can, with practice and skill, be blown out with a cutting torch, leaving the threads undamaged. After the bolt is blown out, use a thread tap to clean the holes.

5. …. a threaded bolt or stud is broken off above-flush (i.e., standing proud) in a blind hole: To drill out the broken bolt, first grind a center in it, and then proceed as in the accompanying illustration above.

6. …. a threaded bolt or stud is broken off below-flush in a blind hole: Probe gently with an ice pick to determine if the broken piece is locked in place or if it appears to wiggle. If it moves easily, this is a good sign. Grind a center in the broken bolt if it is to be drilled out, and begin drilling with a left-handed drill bit; it may spin right out of the hole.
Drive in a piece of wood to prevent nipple collapse.

Drive in a piece of wood to prevent nipple collapse.

7. …. a threaded brass (yellow metal) fitting is broken off in a blind hole: An internal pipe wrench or large extractor will usually remove this kind of fitting. The internal pipe wrench fits inside the piece to be removed. As the wrench is turned, it expands. This action saves collapsing and damaging the fitting during removal. When no internal pipe wrench is available, drive-in a piece of wood and then use a pipe wrench or vise-grip plier on the outside.

8. …. a pipe nipple is to be removed: The nipple will sometimes collapse under the jaw pressure of a conventional external pipe wrench, especially if it is thin-walled. To prevent this, insert a solid, snug-fitting object into the nipple before using the pipe wrench. Even a piece of wood can be driven inside the pipe.

Use a fitting extractor to remove broken fittings.

Use a fitting extractor to remove broken fittings.

9. …. a threaded steel (gray or bright metal) or aluminum fitting is broken off in a blind hole: Use an internal pipe wrench to remove a larger broken fitting, and an Easy-Out style extractor to remove a smaller one. In the accompanying photo an aluminum coolant pipe was broken off in an aluminum intake manifold. A large diameter extractor was first driven into the broken-off stub of threaded aluminum tubing. Then the threaded boss in the manifold was heated to expand the metal around the broken fitting, and finally the broken remnant was turned counterclockwise and removed. (Excerpt from “PRACTICAL BOAT MECHANICS” to be published this fall.)

(Some of this material excerpted from “PRACTICAL BOAT MECHANICS”, by Ben L. Evridge, to be published this fall.)