Be careful on your multi-grade oil

[PhilR]

Just a suggestion.....if your oil pressure alarm goes off, don't assume it is a faulty sending unit. Shut down immediately and take a look in the engine room...it may mean you have no oil pressure!!! Don't ask me how I know.

Phil

 

[JerryE]

I am resurrecting this thread, unfortunately, to ask three questions. My oil pipe broke and wreaked the engine, so Mack Boring in Middleboro, MA (our Yanmar distributor) replaced the engine. The good news is my brand new 4BY150 Yanmar runs at 197 degrees as opposed to ≥204 on my old one. The bad news is that at 28 hours on the new engine, while tooling along at no wake speed, my low oil pressure alarm went off today. I turned of the engine and dropped the anchor having seen this picture before. After searching the engine compartment for oil spray from another bad oil pipe and checking the oil level (all of which was fine), I restarted and got another 10 minutes at no wake speed before that alarm came on again.

I wonder if anyone has a chart of average oil pressure levels at different speeds (under load) starting at idle (750 rpm-no load of course). I bet Mike has this, but I need data for the 150hp and his is a 180hp. I hope I find my pressures are OK despite the annoying alarm which can only be turned off by shutting down the engine. Of course, if I have the same problem Mike had then my pressure readings will be consistently low anyway. Guess I'll have to rig a manual gauge for that–does anyone know if there is a spot(s) for that on the engine and what gauge to use?

Mike, do you have more information about using that Ohm meter to test the oil pressure sending unit? Any help would be appreciated, as always!

 

[GulfSailor]

I wonder if anyone has a chart of average oil pressure levels at different speeds (under load) starting at idle (750 rpm-no load of course...........
.............Guess I'll have to rig a manual gauge for that–does anyone know if there is a spot(s) for that on the engine and what gauge to use?

Two things come to mind. First, your oil pressure shouldn't change with engine load. It changes with engine speed as the oil pump rotates faster and faster until it either reaches the maximum that the pump can deliver, or a relief valve opens.
It also changes with viscosity, and you'll see a higher pressure on starting a cold engine than you will when the oil is up to working temperature. Even the magic of multi-grade oils doesn't change that. 🙂

Adding a mechanical gauge is an excellent idea, and easily achieved. Although you can get a $10 gauge from an auto parts store, I'd recommend a better quality VDO unit, as used in aviation and German sports cars. 😉

http://www.aircraftspruce.com/catalog/inpages/vdopressureoil.php

Installation would be simplest by installing a brass ' T ' in the existing oil pressure switch port, then connecting both the existing OPS and the feed to the mechanical gauge to the ' T '.
If it were me, I'd install the new gauge in the engine compartment, rather than snake a pressurized oil line all the way through the boat to the helm.
That way you can compare the mechanical gauge reading to the digital one at the helm (with the aid of a crew member) and not risk spraying the cabin interior with hot oil should something unfortunate happen! 😱

Lastly, should an obstruction make the installation at the OPS location difficult, you could have a short hydraulic hose made up at NAPA or a similar store to bring to connection point for the ' T ' out to a more convenient location.
However, if you do that, make sure to run a ground connection to the ' T ' or you won't get an input to the digital gauge.

 

[knotflying]

I have the service manual for my engine on the boat, but I am sure if your ohm meter readings may be different than mine. Does your oil pressure rise as you increase RPM's? At max RPM I was getting was only getting 24 PSI which is much lower than the 56 tp 65 at full throttle. The temporary installation of a mechanical gauge would be at the oil sensor. You can remove the sensor and install the mechanical and check the pressure. I would think though that this is an item covered under the warranty and a trip to Mack Boring may be in order. If you want me to get the ohm meter reading values I will take a run to the boat and get the info so let me know.

 

[linedoctor]

I'm glad I remembered this post though at the time I read it I never thought I'd be having this issue....yesterday I did the second oil change on my 6BY and all of a sudden the temp is way up. I was always running about 198. Now (today) I'm at about 205-207. At idle I'm running about 201 when it used to run in the mid 180s or so. At one point today my idle temp was 211 for a short time. Crazy. I'm using Mobil 1 full synthetic 5w40, the exact same as I had before. Should I call the mechanics in or not sweat it? This really put a damper on today's cruise. It's hard to believe an oil change could cause this but it was fine before. Advice is welcome!

 

[abcandjrc]

It's hard to believe an oil change could cause this but it was fine before. Advice is welcome!

I'd concentrate on that statement. Something else has probably happened. Did you do the change, or did a someone else?

Even something like a different contact on the wire to the sending unit could cause a bias. Perhaps moved and contact is better, etc. Raw water valve closed and not fully reopened. Loose heat exchanger fill cap not fully closed was tightened. Just a random, unrelated partial failure of the raw water impeller. I suppose others can suggest even more.

Those water temperatures are not out of line, by the way. A pressurized system will sometimes run over the boiling point of water.

(It probably would have been better to start a new thread. This one is old and tired and I think pretty well beat the subject to death. As I recall, not reading the whole thread again, it was a red-herring issue at that.)

 

[knotflying]

Yes, a new thread may be a better place to run this issue. It sounds more like a cooling water issue than a oil issue. If your temperatures are much different than you normally get than you could have a problem bruing. Perhaps your impeller or like stated earlier a half closed seacock, blocked strainer etc.