Question for all gearheads

[sailaway78]

Here's the situation. I was heading into Biloxi, in the east channel. It is only a little over a mile long, and fairly narrow. Skinny water on both sides. I have a thunderstorm pounding me pretty good. 30+ knots and a very nasty following sea. About half way up the channel, the wind shifts, and picks up. Gusts approaching 60 knots. The boat is pitching with the following seas, and over 35 or 40 degrees to port. Wallowing real bad. I'm managing pretty good, but it's work. All of a sudden something goes off, sounds like a AK47, on full auto. Very loud. And sounds like it's coming from under the boat. My mind is trying to solve two problems at once. What is wrong, and what am I going to do if something breaks. There is no way I can get anything done in this channel before I get blown out of it, and find the bottom. I throttled back to about 1500, the frequency of the noise reduced as the RPM came down, but was just as loud. Then after a lifetime, it just faded away. Real time less than a minute. About 20 minutes later the exact same thing. Again after less than a minute it faded away. And before I got in, one more time. As soon as I got behind Deer Island, into calmer water, it was gone for good. I checked everything I could think of. Oil pressure was a steady 55lbs, water temp @ 135. I thought maybe something had shaken loose and was hitting the coupler. NADA. Today I took her out and played around in some fairly snotty conditions, but could not make it repeat, but I couldn't duplicate the conditions. I can find absolutely nothing wrong, anywhere. Any of you gearheads have any ideas. I have a theory floating around in my heat, but am going to wait and see if anyong else has the same idea.

 

[Manureva]

running out of oil under the oil pick up, making the engine knock on the crank, probably took some life out of your crank bearing....

 

[CarlN]

Agreed. 30-40 degrees of heel? Some Yanmars can lose oil pressure at as little as 20 degree heel - less if the oil is at all low. The pickup tube comes out of the oil. This is one reason to always fill right up to the full mark on the dip stick.

Once you leveled out behind the island the tube was back in the oil and pressure built back up. The only mystery is why you didn't get an oil pressure alarm in the channel. Do hear one at startup?

Carl

 

[anchorclanker]

Yeah if it was heeled over good with the motor running, thats certainly possible. However, I would have thought the manufactures would have considered that into the design and gave it a deep enough sump it wouldn't starve until past 45 degrees?

Most engines that start knocking loudly after oil starvation, continue knocking after oil pressure is restored. One thing you could do is have an oil analysis done on the oil. If any bearings were damaged it should show up.

If we assume it was not the engine, then it had to be in the driveline, between the engine and prop. Is it possible the boat was heeled over far enough the prop cavitated? They can make a lot of noise if they start slapping water.

 

[CarlN]

Nope - small yanmar are converted tractor engines and not designed to be tipped too far.

Here's a response I borrowed from another board from Larry Berlin on the question of oil pressure loss on heeling Yanmars - Larry runs the training courses on Yanmar's at Mack Boring the East Coast importer of Yanmar engines and probably knows more than the Japanese:

This is a common question and there are several answers. All information is only accurate if the oil is at the full mark on the engine and transmission dipstick and the coolant is full.

1. If the prop shaft angle is 8 degrees or less on a parallel drive engine. Constant heel would be 30 degrees or less with peak heel being 40 degrees. NOTE! Peak heel means, The boat is running at up to 30 degrees and hits a wake and heels over to 40 degrees for 10 seconds or less.

2. On a parallel drive, if the prop shaft angle is 8 to 15 degrees, constant heel would be 20 degrees and peak would be 35.

3. If there is an angle drive transmission and the engine angle is O, constant heel would be 30 degrees and 40 degrees.

4. If the engine with the angle drive transmission is installed at an 8 degree angel. The constant heel would be 15 degrees and peak would be 20.


My bet is that your oil was down half a quart. You only have about 3 quarts in your engine right?

Carl

 

[sailaway78]

No and no

Carl,
That info may come from a knowledgable source, but my personal experience does not equal that. I had the pan off my engine last year. The oil pickup is at the very rear of the pan, and i would guess my engine is angled about 15 degrees. With the engine angled more, the more heel it would take than if angled less. Oil was just changed, and was and is full. Also I stated in the origional post that the oil pressure was good and was stable. Never fluctuated a bit. I do agree that once you have a bearing knocking, it ain't gonna just go away. And mine since has not made a sound, and the oil pressure is the same. ( I have a guage on mine, don't lke just a buzzer.)

 

[Gunni]

Interesting point of view regarding oil levels. I delivered a boat with a Perkins aux in it and the owner insisted that the oil level stay at the lower limit to prevent oil reaching the piston skirts on heel. Generally don't like to motor when heeled, but as N&E demonstrates, sometimes it happens.