Yanmar 6BY2-260 oil pressure

[henningbuus]

A few months ago I lost all the engine oil while running at high RPM. The Yanmar 6BY2-260 is made by BMW and Yanmar converts it to a marine engine. In that process, an engine oil pressure sensor located below the oil filter and pretty much out of sight, is not being used in the marine application. That sensor had unscrewed itself and the oil pump just ejected all the oil into the bilge. Now I am worried that the engine bearings suffered some damage, so I recorded the oil pressure at various rpms and engine temperatures, and would like to know if this is normal. They are as follows:

Engine rpm engine temperature Oil pressure
1200 116 33
2000 182 31
3500 194 45
3500 202 40
3000 204 35
2500 203 23
2000 199 18
1500 197 16
1000 196 11
670 195 7

The Yanmar Service Manual specifies 51 - 87 psi at 4000 rpm, and 8.7 - 14.5 at 1000 rpm, so it appears that my engine meets that, but 7 psi at idle seems very low, and I belive the oil pressure warning comes on at 6 psi.
I would be interested in knowing if any of you with this engine have similar oil pressures.

 

[rpmerrill]

My 4BY2 with 1000 hours runs up in the oil pressure range that you quote. (60's-70's)
The only time it is down in the low numbers (30's-40's) that you are getting is at idle.

I had never heard about a pressure sensor down under the filter. (Wow, I'll bet you had a real mess!)
There is a sensor on my engine up on top, forward on the starboard side.
I've never heard a good answer on this question but as I understand it, this sensor measures the pressure but it doesn't seem to be the "alarm" sensor. I've had it malfunction and have even run with it disconnected.
I never was able to find out where the alarm signal is generated.

You didn't mention that you had recorded your numbers from a time before the spill.
What alerted you to the spill when it happened?
I'd suggest your next step would be to install a pressure gauge in place of your sensor, to be sure it is reading correctly.

Good luck.

 

[knotflying]

Historical data from your engine would be a better comparison. As I posted on your other post, I don't think these numbers will necessarily indicate bearing damage. 7 PSI at low idle seems low as does your idle RPM. I would think that idle should be around 800 or so and this may be why the pressure is reading low. Also keep in mind that the pressure readings (IMO) are not highly accurate and fall between a range since the information is converting from ohms from the sensor to a computer which then gives you the number. The most accurate is a mechanical gauge. Time will tell if there is bearing damage. However, you may want to do a couple of oil analysis readings at a couple of oil changes and see if there is a trend of wear going on.

 

[marcham]

You could collect an oil sample and send it in for analysis, that could tell you if there are abnormal metal levels in the oil.

Sent from my SM-T720 using Tapatalk

 

[knotflying]

I had never heard about a pressure sensor down under the filter. (Wow, I'll bet you had a real mess!)
There is a sensor on my engine up on top, forward on the starboard side.

I never was able to find out where the alarm signal is generated.


Good luck.

If you look you will see there is a sensor under your oil filter housing. This is the second one I know of that developed a leak. The first one was just a drip. Not a bad idea to put this on the periodic maintenance list.
I think the ECU monitors the pressure and when it gets low it will send a signal to the Yanmar display to give you the low oil pressure warning. Hence, when they did the software update I think they just updated the software to convert the ohms to pressure conversion to boost the pressure reading a bit.

 

[scross]

Relying on those oil pressure numbers assume that the sender is sending you absolutely accurate data - what may or may not be true. I agree that comparing current pressure readings to past pressure readings would be the best way to check if there has been a change in pressure at various RPMs since your incident.
Second the suggestion on sending an oil sample to Blackstone for analysis. I have been using them for almost a decade now and their insight into the oil readings are very, very informative. Great thing to do before buying a used boat.

 

[captstu]

There are two service bulletins outstanding on the 4BY series of engines. Both were published by Ranger to Tug Nuts and should be available on the Tugnuts site.

One relocated the oil sensor from the port side near the filter to the starboard side above the heat exchanger.

The second re-wired the sensor using a different routing on the wires and re-programmed the analog digital converter so you have higher pressure readings. That service bulletin has been a source of significant problems to those of us who had it put on.

There is no easy way to tell if that service Bulletin has been put on. I would suggest that you get a mechanical oil pressure gauge and see what the real oil pressure is that your engine is seeing.

The mechanical oil pressure gauge that I used to test my engine read about twice what the oil pressure gauge read before they put the service bulletin on my engine. After the installation of the service bulletin by Yanmar authorized dealer had a second dealers attempt to repair the damage the first dealer is done, my oil pressure now reads nothing. Not zero, just blank. Yanmar installed an idiot light pressure sensor to give an indication of failure if there is one.

This is truly a Humpty Dumpty issue. If you don’t put on the service bulletin the pressure readings are not indicative of the actual pressure. If you do put all the service bulletin there’s a chance you’ll have no pressure readings at all and like Humpty Dumpty they can’t put it back the way used to be.


Stuart Bell
Ranger 25: Shearwater
(561) 352-1796