BLEED THE FUEL
MAXIMUM RPM TABLE
PARTS AND TOOLS
RAW WATER PUMP
SET THE IDLE RPM
' V ' BELT ADJUSTMENT
WATER IN THE ENGINE
WATER IN THE FUEL
The Nav Station...
Yanmar Pleasure Boat Marine Engine Help
FREQUENTLY ANSWERED QUESTIONS
1. Q: I have some difficulties of starting up the high pressure fuel pump on the YSB8. We have overhauled the engine but since the pump worked fine before, therefore we are suspicious that some "stopping devices" have been engaged. Does anyone know of any such mechanism, and if so, how to disengage them?
A: The fuel line must be bled in sequence. My YSB-12 has an electric lift pump. Turn on the lift pump and the bleed the engine mounted filter. Then bleed the line to the high pressure pump at the bleed screw on the side of the pump. Then loosen the pipe at the injector and bleed the injector line. On my engine, the line to the injector will not bleed unless the throttle is advanced. If you do not open the throttle, no fuel will be delivered to the injector and the line cannot be bled. I hope this is helpful. ( contributed by Joe Mac Phee )
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2. Q: 3QM30H. When the motor is operating at what feels like normal operating temperature, the exhaust bellows large amounts of steam.
A: A salt water cooled engine operates at about 55degC / 130degF. This means it is quite easy to keep your hand on the cylinder block while the engine is running. If the temp goes over this the salt will precipitate out of the water and restrict the water galleries at an unacceptably fast rate. Because of this the alarm operates at 62degC / 144degF. The steam from your exhaust indicates that the water flow thru the engine may be too low.
Check the following:
i) That there are no restrictions in the intake from the sea cock to the pump. You must dismantle everything if you haven't already and look inside or poke something thru that will remove jellyfish, small leaves, barnacles, etc.
ii) The hole in the thru-hull fitting sometimes gets smaller and smaller with each successive coat of antifouling. Go for a swim and check the hole is the right size. Don't rely on blowing through the system as it has to be very blocked up to provide any resistance to your huff.
iii) Where the water supply enters the cylinder block it splits and goes up to the thermostat bypass. When the thermostat is closed there is no significant flow through the block and head. When the thermostat opens it allows water to flow through the block, head and exhaust manifold to join the exhaust gas at the mixing elbow, and at the same time cuts off the bypass water flow. If the steam is intermittent the block, head or exhaust manifold galleries are restricted as the steam appears when the thermostat opens wide. I have not had any experience with Salt Away so I don't know if it works well or not. The white stuff you can see when you replace the anodes is a combination of extinct anodes and salt.
iv) On some model engines the thermostat cover can be installed in reverse. Check to see if it is the right way round, the word 'in' is usually embossed on the end nearest the front of the engine.
v) Check the raw water pump. You may find the wear is unacceptable and an overhaul is necessary. Check the cam, the cover plate and the inside face where the impeller runs and re-surface or replace if there are any grooves. Replace the impeller.
vi The exhaust manifold should be removed, dismantled and the water galleries cleaned. You have already cleaned the gas side and replaced the mixing elbow. It is possible that the manifold may need replacing at this age.
vii) The worst scenario is a cracked cylinder head leaking water straight into the cylinder while running. If you do things in the order laid out above they go from the more probable and the least expensive to the least probable and most expensive.
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3. Q: I have a 2QM20, which repeatedly gets air into the fuel system. After completely bleeding the system (at the bleed screws on the fuel distributor and filter as well as the injectors themselves), if I run for a few hours I can bleed air again and again. If I slack off, the engine will eventually fail. I have a Racor 500FE between the tank and the engine, which I have filled by hand with fuel, although whenever I open it there is always about an 1/2" of air at the top. Everything has been replaced: tank, fuel lines, filter elements, gaskets, etc. Unlike this fuel schematic the return line goes to the primary filter.
A: The return line is your problem. It must be returned to the top of the tank as the fuel aerates under high pressure at the injectors and this aeration cannot escape unless it is dumped into the top of the fuel tank. It is being recycled thru the system and you have to let it out. I have come across this several times before. If you have difficulty fitting a fuel return to the existing tank you can 'T' it into the tank vent hose or the tank filler hose where the fuel can drop into the tank.
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4. Q: My Yanmar 3GM30 is putting antifreeze into the overflow reservoir at about a cup an hour. I discovered this by finding a puddle under the engine after each day of motoring for 3 to 4hrs. I have replaced the thermostat and the heat exchanger cap but no change. Each morning after motoring now I pour the excess antifreeze from the overflow back into the heat exchanger and it fills back to the top. Are there any tricks I can do to evaluate the head gasket vs leaks in the heat exchanger tubes? I see no antifreeze in the exhaust discharge and have not experienced any overheating (yet).
A: Some overflow bottles have two tubes to which you can connect the hose from the header tank. The hose must be
connected to the one that goes all the way to the bottom of the bottle. If it is connected to the other one it will blow coolant into the bilge (all around the engine room on a big horsepower engine) and wont be sucked back.
Other causes to look for are a faulty heat exchanger cap (I see you've replaced that) or a cracked filler neck ( the problem in this case ).
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5. Q: My engine thermostat is set to start opening at 105 and be fully open at 112. I think this is much to low but it is the original stat from Yanmar. The oil never gets hot enough to burn off the byproducts of combustion. The temperature gage never gets over 100, even after motoring all day.
A: A salt water cooled engine operates at about 55degC / 130degF., you can keep your hand on the cylinder block while the engine is running. If the temp goes over this the salt will precipitate out of the water and restrict the water galleries at an unacceptably fast rate. Also, because of this, the alarm operates at 62degC / 144degF. The raw water cooled engine thermostat starts opening between 104 -112deg F and is fully open at 125deg F. Because the reading is quite low gauges are often inaccurate, and may be a reason yours only reads 100degF most of the time. Most gauges are the same except test gauges which are not practical and very expensive. Even with freshwater cooled engines, that operate at higher temperatures, the oil retains the byproducts of combustion and always looks black. The best way to help get rid of contaminants is to rev up the engine for a half minute (over 3000rpm), out of gear, before moving the lever back to idle and shutting down. Do this at the last stop of the day if stopping and starting a
lot. Also run the engine at 3000rpm or over for 10 minutes or more, for every 5 hours of slower running. 2000- 2500 is very slow. The engine will prefer 2800rpm or thereabouts.
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6. Q: My engine has a tendency to fire and run backwards for a couple seconds if I take my finger off the start button too soon or if the battery is a little low and the cranking speed is slow. Is this normal or is the injection timing off. (the engine is definitely running backwards as it runs very rough and exhaust comes out the air filter)
A: Yes, the single cylinder engine can do this occasionally. If the battery is low use the decompression lever to get some rpm before closing it and firing the engine. If the timing is out the engine will not run at all. N.B. It is possible the air silencer foam element will have a hole blown in it and should be replaced.
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7. Q: The engine seems to suck in aerated fuel. other than fuel lines on the suction side of the fuel pump leaking at the fittings are there any problems with the pump which may cause this.
A: Does the engine slow down and stop? If the diesel tank is above the lift pump and places where the air is sucked in fuel will leak out while the engine is stopped. Before running the engine one day take a folded paper towel and wipe the edge around every connection from the suction side of the lift pump back to the fuel tank. Any fuel leak will quickly show. All leaks must be stopped. The copper washers on the lift pump banjo fittings often leak if disturbed and must be replaced each time. The o-ring on the engine fuel filter is also a source of leaks if not fitted properly and the bleed screws can be stripped as they are little and many peoples hands are strong! Another common problem is that the return line is not put back into the top of the fuel tank. If it is connected back into the fuel feed line the fuel will become aerated. If you are only seeing aerated fuel in a clear fuel return line from the engine back to the tank, this is normal.
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8. Q: The engine came with a 35W Hitachi alternator that only runs slightly faster than crank speed. When running at 2000 - 2500 cruising speed, the alternator doesn't seem to put out much. It seems like the alternator should be turning at least twice as fast as the crank. (Especially when the max engine speed is 3000 RPM and the engine never runs there. I believe the alternator pulley is 3 5/8 inches in diameter and the crankshaft pulley is 4 1/2 inches in diameter.
A: The alternator will achieve its rated output at full engine rpm 3600. If you want 9hp in the water the engine must be able to reach 3600rpm. At your cruising rpm the alt will put out a max of 20-22 amps. Note that an alternator is regulated so that the fuller the battery the lower the output. Once the battery has recovered from a start, an ammeter will fall to nearly nothing. If you have
two batteries charge the engine battery first and then switch it off so that the full output from the alt can charge the house battery. There are aftermarket fast charge regulators available but I don't think the little 1GM10 will handle the extra horsepower at low rpm that they demand.
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9. Q: I was bleeding my 13 H.P. Yanmar 2GM and I over-tightened and stripped the bleed screw on the secondary fuel filter. When I tighten it it just spins. Is there any way to fix this without replacing the entire assembly?
A: Not really, it is a fairly common problem you have there. You may be able to drill and tap for a larger screw / bolt but if you have to pay someone to do it, it may be more cost effective to replace the assembly. Use a short spanner when tightening the bleed screws to help prevent over tightening.
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10. Q: Turbo washing. The manual for the 4JH3TE recommends injecting soapy water into the air filter at high rpm to wash the turbo blades. This does not sound like a great idea, water in the intake. Is this really needed? If turbo washing is needed is soapy water the best solution to use?
A: I agree, soapy water doesn't work very well and doesn't clean 'right around the bend'. It is OK to spray the recommended amount (about 25cc)into the intake at 3/4 power though. Yanmar market a product called TURBOWASH which I recommend as the only product to use. It really works. I was originally sceptical but experience showed it is great, helping cleanout the
intercooler also. I suspect the soapy water idea was because dealers, distributors wouldn't carry the TURBOWASH. See your local dealer and insist that they carry this great product.
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11. Q: Well I FINALLY fixed my black water/low RPM problem on my 2GM20F. The mixing elbow was coked SOLID, such that when I removed it and blew into it no air got through. I replaced the elbow and now things are much better. However I replaced my prop over the summer when the engine was still having problems. The prop I am now using is a Campbell 3-blade Sailor prop (14x9). I get to hull speed at about 2500 RPM and max out at about 2900 RPM. I don't get any black smoke going past this point, just no additional RPM. In reverse at the docks I can spin it at 3600 RPM. The design of the Campbell prop is such that the blades are an airfoil shape and slightly cupped at the end. My boat is a 10,000 lb. Yankee 30. I'm thinking that I might need to go to a 14x8 prop. Is there anything else I should look at before switching props? Also I get a little white smoke at RPM above 2000. I'm due for an oil change so I'll see if that corrects it. Anything else I should be looking at?
A: The prop for your boat will depend on the gearbox ratio. The ratio is on the box data plate. I have assumed a hull speed of 6.7 knots. 2.21:1 = 13X7 inches 2.62:1 = 15X8.5 inches 3.22:1 = 17X10 inches. I suspect the prop is for a 2.62 ratio but your box maybe 2.21 ratio which will give the performance symptoms you describe. Just ask the local prop shop to take an inch off the pitch, without the cupping, if this is the case. White smoke is usually low compression or a little water in the fuel, not enough to stop it. If it is actually steam then there is not enough raw water flow as you increase the power. This may correct itself when the rpm is raised. (Same amount of fuel but more cooling water.) If it is using oil then I suspect that slow running has glazed the cylinder bores, go motoring and give the engine a good hard, long run after you've changed the prop pitch.
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12. Q: What is your recommendation for the time between a transmission oil change for the 4JH3TE motor? Or do you even recommend changing the trans oil?
A: For pleasure boat applications, every three to four years or 500 hours. Three for a KBW21 gearbox with ATF fluid and four for a KM4A down angle gearbox with engine oil.
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13. Q: I've come to a point on my 1GM10 where I'm ready to test drive the engine on a stand before I install it in my boat. I replaced the cylinder and bearings and it's all together ready to go (I think). I don't want to run it without knowing if I need to attach an exhaust hose muffler. I'm thinking it may need the back pressure from a muffler. Any thoughts?
A: No, an exhaust pipe or muffler is not needed unless you need to stop the water spraying around the shed. Put a short piece of hose from the water pump into a bucket and run the hose from the water supply into the bucket, that way you will know the pump is working. Run the engine for about 5 minutes, just long enough to satisfy yourself that the engine will run reliably when you put it in the boat. When you're in the water run the engine in gear in fwd and reverse while tied up, again just long enough to check it will idle when warm and reach max rpm, then go motoring. Vary the rpm every 20 minutes up to 3000rpm for the first hour then take it up to 3600 for a couple of minutes. After that, smile and go sailing. Check the tappets and change the oil at about 20 hours or 1 month, whichever is the sooner.
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14. Q: Do I need a special right angle screw driver to get to the impeller/cover plate on the 2GM20F. I looks like a tight area to get to. Am I looking at this wrong, the pump is on the lower starboard side, forward. A mechanic I am not.
A: From the front of the engine, loosen the hose clamps and then the bracket (2 bolts) that holds the pump onto the engine. Swing the pump toward the center and take off the v-belt. Totally remove the mounting bolts and pull off the hoses, you will have the pump in your hand.
You need a 10mm socket to undo the 2 bolts, a plus and minus screwdriver to remove the cover plate and a pair of pliers to pull out the impeller. Be careful you do not damage the pump body as it is only brass and therefore quite soft. e.g. dont lever the impeller out with a screwdriver or something.
When you refit the pump do up the 2 long bolts with your fingers, fit the v-belt and pull the pump body firmly away from the center of the engine, dont use a lever! While holding the pump firmly away from the engine do up the inner bolt first and then the outer one.