Yanmar Tips

[GordMay]

Caveat emptor: E. & O. E. - While every endeavour is made to ensure the information in this posting is correct, please email me if you find any mistakes so that they can be corrected.

SOME YANMAR DIESEL ENGINE TIPS:

Sizing:
Rule of thumb for Horsepower Required:
Sailboat or displacement launch: one horsepower per 500 pounds ( plus/minus 50lbs ), one kilowatt per 170kg of fully loaded boat is enough to punch into an average seaway.

Operating Temperatures & RPM:

Fresh-Water Cooled engines do not require long warm up periods. By the time you start the engine, check all clear, cast off and get out of the marina or in a clear area the temp will be over 60 Deg. C (140 F), displacement vessels can go straight to cruising power, once clear of the marina. Prolonged no-load operation of the engine will cause it to blue/gray smoke at low rpm with an associated increase in oil consumption. For every 3-5 hours low load operation (trolling) or no load operation (running the fridge or charging batteries) should be countered by 20 minutes near maximum continuous rpm.
Raw water cooled engines: As the operating temp is only 55 deg. C (131F), provided the engine will keep running in gear, the clutch can be engaged. Apply cruising power about 5 minutes after you start moving.

When increasing engine rpm take about 10 seconds to move the throttle lever between low load and full load.

Because a Raw Water (salt) Cooled Engine operates at about 55 Deg. C (130 F), 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 62 Deg. C (144 F). The raw water cooled engine thermostat starts opening between 104 -112deg F and is fully open at 125 deg F. Because the reading is quite low, most gauges are often inaccurate, except test gauges (not usually practical and very expensive).

Freshwater Cooled Diesel Engines operate at higher temperatures (60 Deg. C - 140 F) than Raw Water Cooled Engines.

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 oil contaminants is to rev up the engine for a half minute (over 3000 rpm), 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 3000 rpm or over for 10 minutes or more, for every 5 hours of slower running. 2000- 2500 rpm is very slow. The engine will prefer 2800 rpm or thereabouts.

Do not operate for extended periods below 80%maximum rpm. The cylinder bores will glaze, causing an increase in oil consumption and blue smoke. Don't 'baby' your diesel engine!
TIP:
If you’ve ever forgotten to turn on the raw water supply, before starting the engine - put the engine key on the sea cock every time you turn it off.

For engines without a tachometer, run it where it sings best. If the ship is shaking and growling, alter the RPM. If the engine VIBRATES unpleasantly at a particular rpm, don't operate it in that rpm band or it will eventually break!

Yanmar TACHOMETERS usually read about 100rpm too high at maximum rpm (and they aren't adjustable), so don't be pedantic about lining up the needle exactly.
You may note that the MAXIMUM RPM of your engine under load is higher than the figure I have given below.

USE THE MAXIMUM RPM IF YOU ARE IN TROUBLE, don't be frightened, the engine will handle this for an hour, provided it has been installed correctly. Once out of trouble, reduce rpm to 85%, for better fuel consumption and longer engine life.

IDLE RPM by Yanmar engine model:
Engine model Hand-held tachometer Boat engine Tachometer (Instr. Pnl.)
GM series 825 rpm 875 rpm
JH and JH2 series 775 rpm 825 rpm

MAXIMUM* RPM by Yanmar engine model:[/i]
[i]Engine model Hand-held Tachometer Boat engine Tachometer
GM series 3550-3650 rpm 3650-3750 rpm
JH and JH2 series 3600-3650 rpm 3750-3800 rpm

* Fully loaded, clean-hulled boat, at speed.

For prolonged running, a pleasure boat engine should operate at about 85% of maximum continuous RPM.

CRUISING RPM (Yanmar):
GM, JH, JH2 series about 2900rpm

Propellers:

The propeller controls the maximum rpm under load. On Sailboats, there is no substitute for propeller diameter. Fit the largest diameter prop that will fit in the space (aperture) available*. You need to take into account the available gearbox ratios.
e.g. a 3GM30 with a 2.36:1 ratio gearbox will swing a 15 inch (380mm), a 2.61:1 ratio will swing a 16 inch (405mm) and a 3.2:1 ratio will swing an 18 inch (460mm) diameter propeller.

*Prop’ Clearances Rules of Thumb:
- The clearance between the tip of the prop and the hull = about 15% of Propeller Diameter
- The clearance between the rudder and the nearest point of the propeller = about 15% of Prop’ Diameter

- The clearance between a full keel and the leading edge of the propeller, measured half way out along the blade from the center of the shaft = about 30% of Prop’ Diameter, at half the radius from shaft centreline.
- The clearance between the prop strut bearing and the propeller hub = about equal to or 1.5 times Shaft Diameter.

Fit as large a diameter propeller as possible, taking into account the available gearbox ratios.
e.g. a 3GM30 with a 2.36:1 ratio gearbox will swing a 15 inch (380mm), a 2.61:1 ratio will swing a 16 inch (405mm) and a 3.2:1 ratio will swing an 18 inch (460mm) diameter propeller.

Propeller pitch is determined by boat speed and is calculated for individual boats.

Engine Gearbox Propeller diameter Recommended
model model ratio Inches millimeters Max. Displacement
1GM10 KM2P 2.21 12 295 < 5,000#
2.62 13 325
3.22 15 370

2GM20 KM2P 2.21 13 340 < 10,000#
2.62 15 375
3.22 17 425

3GM30 KM3P 2.36 15 380 < 15,000#
2.61 16 405
3.20 18 460

* Rotation: All Yanmar Engines are 'Righthand' (RH) Clockwise rotation, EXCEPT for Saildrives, which are 'Lefthand' (LH) or anti-clockwise.

Ventlation:

Diesel Engines need Air to work properly:
Combustion Air (by weight) approximately 15kg of air (33 Lbs) to 1 kg (2.2 Lbs) of fuel
and for Cooling.

The maximum temperature of the engine room should never exceed 60 degrees C (1400 F) within 20mm (3/4") of any electrical equipment and 450 C (1130 F) at the air intake.

Ventilation Requirements for Yanmar Diesel Engines:
Yanmar Duct Sizes (2 Required - 1 Supply In & 1 Exhaust Out)
Engine Square cm Square inch Diameter
1GM10 19.5cm2 3.02in2 50mm - 2"
2GM20 39cm2 6"2 75mm - 3"
3GM30 48.2cm2
3HM35 74cm2
3JH2E 84.5cm2
3JH2-TE 120cm2
Tip:
multiply cm2 by 0.155 to get inches2
100mm inside diameter tube duct area is 78.54 cm2
50mm inside diameter tube duct area is 19.7 cm2
4 inch inside diameter tube duct area is 12.57 inches2
2 inch inside diameter tube duct area is 3.15 inches2

Note: TWO ducts the same size are required, one inlet and one outlet.

Bleeding Air from the Fuel:

Caution All engines: If the engine does not start on the first attempt, turn off the raw water cock. When the engine starts, turn on the cock immediately. Prolonged cranking with the raw water turned on will fill the engine cylinders with water!

Bleeding GM Series Engines:

1. Open the small BLEED SCREW on top of the engine mounted fuel filter and operate the fuel lift pump by hand.

2. After the fuel filter has been purged of air, close the bleed screw (don't do it too tight, it's only little) and open the one on the fuel injection pump.

3. Again, after the air has been purged, close the bleed screw.

- The engine should now start, if not you will have to bleed the high pressure side as follows:

4. Crack the pipe nut at each injector, open the decompression levers and rotate the engine with the starter motor.

5. When the air appears to have been purged (the fuel looks clear, not whitish or frothy), tighten the nuts firmly, close the decompression levers and start the engine.

- Check for leaks and clean up any spilt fuel.

TIPS:

1. If the HAND PRIMING LEVER doesn't have any resistance through any of its travel, rotate the engine crankshaft through 360deg. Use the starter motor or crank handle.
There is no resistance to the hand priming lever because the internal actuating arm is on the top of the cam that drives it. Rotating the engine crankshaft 360deg will turn the camshaft 180deg, the arm will now be on the back of it's cam and you should feel resistance when operating the hand priming lever.

2. Put a rag or paper towel around a loosened bleed screw or injector pipe nut to retain the diesel that will leak out.

3. Use a folded paper towel or toilet paper to check around joints for leaks. Leaking fuel will quickly be absorbed by the paper and stand out like the proverbial....
4. Clean the engine bay, or any other affected area, with a lemon scented dishwashing liquid to get rid of any diesel smell.

5. One lousy day, when you're bored and have nothing else to do, paint the heads of the bleed screws red, it will help you find them when the heart is pounding, the stomach is heaving and the S#*T is about to hit the fan.

6. SB, YSB and YSE engines: To bleed the injector line the throttle lever must be in the full power position.

7. Some engines have a HAND PUMP on top of the fuel filter, push it up and down. You may not need to open any bleed screws as the aerated fuel is sent back through the return line to the tank.

WINTERIZING or De-Commissioning:

RAW WATER COOLED ENGINES:

1. Open the cylinder block, exhaust mainfold and waterlock drains, leave them open.

2. Drain the water intake filter and leave the seacock open.

3. Remove the air cleaner, open the decompression levers. While turning the engine over with the starter motor, spray CRC 'Longlife' into the air intake for about 5 seconds per cylinder.

4. Close the decompression levers and refit the air cleaner. Put a plastic bag or similar over the aircleaner so air can't get in.

5. If you have an exhaust outlet valve at the transom, close it and put the engine key on it !

5b.If you dont have a valve, put a rag up the exhaust and seal it with plastic and tape or something so that air can't get in. Do something clever with the engine key so that you remember to remove the obstruction before starting the engine !

6. Wipe a thin smear of grease over the control cable end where it attaches to the engine. Do the same for the stop cable.

7. Remove the battery and take it home to charge it occasionally. If you can't remove the battery at least remove the terminals and give them a light grease, leave them off till Spring.

8. Clean the engine room.

9. I think it's time for a rum and coke .

FRESH WATER COOLED ENGINES:

1.If the coolant needs replacing, do it now. N.B. You need to be able to run the engine to do this properly.

2. Open the raw water drains on the heat exchanger manifold, gearbox oil cooler and where ever else they are on your engine. Open the waterlock drain.

3. Remove the silencer. While holding the stop button, press the starter button and spray CRC 'Longlife' into the air intake. Take about 10 seconds per cylinder with stops every 10 seconds to admire the view. ( and let the starter cool down )

4. Refit the silencer, cover it with a plastic bag and seal it.

5. Blank off the exhaust outlet and put the engine key somewhere clever so that you remember to remove the obstructions come Spring.

6. Wipe a thin smear of grease over the control cable end where it attaches to the engine. Do the same for the stop cable.

7. Remove the battery and take it home to charge it occasionally. If you can't remove the battery at least remove the terminals and give them a light grease, leave them off till Spring.

8.Clean the engine room.

9. It's definitely time for a rum and coke .

Caveat emptor: E. & O. E. - While every endeavour is made to ensure the information in this posting is correct, please email me if you find any mistakes so that they can be corrected.

Best regards, and happy motoring (when you can’t be sailing),
Gord

[CSY Man]

Hi Gord.

Thanks for interesting operating tips.

As for the Max continous RPM, you say 85%.
Is still a special recommedation for Yanmar due to their designs, or is it general for most diesels?

I have heard 70% of max contious as the target, and have been running my Perkins 4-108 at that speed:
Max RPM 4000, max contious 3000, so I have been running at 2100 RPM and the engine seems to like it..No smoke, fuel consumtion 0.55 gallons per hour, minimal oil consumption and no vibration.

85% would be 2550 RPM, and it seems kind of "busy" at that speed.

My engine is now 25 years old and to the best of my knowledge have never been overhauled, therefore I would like to run it "easy" to get some more life out of it.

[GordMay]

CSYman:
First - I’m NOT a diesel mechanic, nor do I have any significant Perkins 4-108 experience (never owned one).

I’ve noticed that many T-108 owners achieve cruise at (hull-speed) at between 2000 and 2250 continuous RPM.

I’ve seen Generator instructions that specify 70% Max. RPM for continuous duty.

Cruising RPM is very much a function of the transmission and the propeller size/pitch. One way to establish proper "cruising" speed, is to use a GPS on calm water - and gradually increase the RPM, as you monitor the "ground speed" (SOG). At some point (about 2100 RPM on your boat ?), theSOG speed recorded by the GPS will not increase - to go beyond this simply uses fuel and overly exercises the engine.

I’d say that you are probably wise operating at around 2100 RPM, given that you get:
- good fuel efficiency
- no smoke
- min. oil consumption
and
- no increase in speed at higher RPM’s ?
- proper operating temperatures ?
- hull speed @ 2100 ?

Sorry, I cannot be more specific - I’m just not quualified.

HTH
Gord

[CSY Man]

no increase in speed at higher RPM’s ?

Well, Gord:

I DO get quite an increase in speed by going past 2100 RPM.
At 2100 I get 5.2 knots
Going to 3000 RPM I can obtain 6.4 knots in calm water.
4000 RPM and I go more than 7 knots, BUT the stern is digging in, foam is flying and hull speed is right there...(6.7 knots according to the old formula, plug in a few extra factors and the theoretical hull speed is about 7.2 knots. ref:

http://www.image-ination.com/sailcalc.html


That is however pushing the hull speed and drag increases with fuel consumption and noise and wear and tear of course.

Have tried to put on my spare prop which is pitched higher and then get into an "over-propped" situation...The engine did not seem to mind with the bigger prop, but the internal pressures goes up and I am not sure if that is good on an older engine.

Have heard somewhere that with a correct size prop ya should get 90 % of max RPM while in gear and tied to the dock.
While running free, 100% RPM.

If one is over-propped, one will never get max rated RPM...?

[GordMay]

CSY:
I'm not entirely comfortable with everything you're telling me.
I'll have to give it some more thought (as I get time), and will reply further...
Gord

[CSY Man]

I'm not entirely comfortable with everything you're telling me.

No?

Would I BS you Gord...?....

Seriously though, the numbers on my boat is the real Mc. Coy based on speed trials in calm water and with a tach that has been calibrated.

The prop is 10 X 16, wide 3 blade.

The upper speed range, 3000 to 4000 RPM is only for emergency conditions as the engine slowly overheats if I run at 3000 or above.
Have overhauled the cooling system, impeller etc, but found nothing wrong.
Can only conclude that it is a problem with the thermostat and or warm waters around here.


As for overpropping..The Dashews in their bible, "The Cruising Encyclopedia" or whatever the big red book is called, actually recommend overpropping to a certain extent....Think the number was 85% of max obtainable.

Let me know your thoughts after ya have mulled it over...

[BC Mike]

You should be able to get full revs while in gear and underway. If you can not get full revs you are working the engine too hard and using too much fuel and creating more heat. You do not have to run it at full revs but should be able to attain full revs. Usually the last 1/2 knot or so is waisted energy. I do 3000 in neutral with my 15 hp Yanmar, I get 3000 at 6.5 knots but usually back off to 5.75 to 6. There is an excellent Yanmar help site available.
BC Mike C

[GordMay]

There are so many variables that this really gets complicated!

I think that, whatever speed (rpm’s) you are comfortable with, might be OK as long as your engine is able to maintain a high enough operating temperature.
At design operating temperatures, RPM's or boat speed are probaly not that important. However, most diesels cannot attain operating temperature without being under some load, hence the cautions regarding low-rpm cruising speeds (underloading). Operation below proper temperature produces carbonization, (soot build-up & cylinder glazing, etc), and that ultimately affects performance and longevity.

Unless you have access to expert and specific advice, I suppose you'll have to rely on the basics:
- Proper operating temperature
- Absence of smoke
- Fuel Efficiency
- etc...

FWIW
Gord

[BC Mike]

The raw water cooled Yanmar does not run very hot so that the salt is not removed from the water are clog the passages in the engine. Motoring with a sail assist does not put much strain on the engine and does cause the repair shop concern, but there are times when this is a good idea. If the motor gets to drive the boat munder load now and then it should be okay. BC Mike C

[Sunset Key]

The original post has conflicting information (see below). Should you run a JH2 engine at 85% of max RPM (3200) or the 2900 RPM listed under Crusing???



MAXIMUM* RPM by Yanmar engine model:[/i]
[i]Engine model Hand-held Tachometer Boat engine Tachometer
GM series 3550-3650 rpm 3650-3750 rpm
JH and JH2 series 3600-3650 rpm 3750-3800 rpm

* Fully loaded, clean-hulled boat, at speed.

For prolonged running, a pleasure boat engine should operate at about 85% of maximum continuous RPM.

CRUISING RPM (Yanmar):
GM, JH, JH2 series about 2900rpm

[GordMay]

Mike:
Any rule of thumb will be approximate (note: I specified "about" values).
For specific recommendations, consult your manufacturer's manual; but don't panic if you're not exactly on their number.

[Wotname]

Great post Gord, thanks for putting all that Yanmar info in one spot (you might guess I have a Yanmar - 2GM20 - )

[Alan Wheeler]

I already have this in the Study Hall, but, here is the general rule of thumb.
All Diesels have a Maximum intermittent RPM rating. This is NOT the same as the maximum continuous RPM rating.
Out of gear, you should be able to rev your engine to it's maximun continuous RPM. Max intermittent RPM is not required and thus, the maximum RPM that the engine can reach can be limited by the throttle stop screw. It serves no benefit to limit the RPM even lower.
In gear, your engine will most likely not reach Maximum RPM, due to the load. HOWEVER, it should be able to at the very least, reach within 10% of it's maximum Continuous RPM limit. Any further than 10% and you are overloading the engine.
Operating a correctly loaded engine in RPM ranges lower than the max continuous range is quite OK for the engine. Operating the engine at very low RPM, certainly idling for long periods of time, is not good for the engine. But do understand that this is for extended periods of time.
Do go to the study hall and read the information there. Including warm up of a Diesel. Warm up is where some of the greatest damage to an engine can occur.

[Sunset Key]

"Do go to the study hall .." is not meaningful to me. Directions, if you please?

[Alan Wheeler]

OK, the "Study Halls" are at the head of each Forum, if the Forum has one of course. If you enter the site via the "home page portal" you don't see each individual forum. If you go to the top of your page, you will see the Tab in the middle top row simply called "Discussion Board". Click on that and you enter the site seeing all the individual forums. Now when you enter a Forum like this one on "Engines: Gasoline or Diesel", you will see the post that is set as a Sticky, "Study Hall". Hope that helps.