Universal M18 leaking oil / low oil pressure

[Ralph Johnstone]

That line that Ralph asked about looks an awful lot like a sensor line for a manual oil pressure oil pressure (non electric).

OMG, you don't suppose this boat was built by British Leyland Motors in the UK with all their crap dashboard gauges. Oil pressure was a tube to a Bourdon tube pressure gauge in the dash. Speed and RPM were high speed rotating spring wire within cables which led to the dash (think engine stop cable.) There was also temperature readout but it was not electrical. It was as if they had never heard of electricity. Hopefully not.

As its a switch, i am assuming the PO didn't like not having a guage and added the box as an upgrade that later failed catastrophically (note the wobbly reconstructed side)

If wobbly is the case, I'd suggest removing the box and consider any "T" joints be done with solid piping (1/8" NPT) or other small but solid assembled piping.

If you can supply answers to questions by others along with an overwhelming number of pictures dealing with these areas, this would go a long way to solving this mystery.

Just remember, never in the history of SBO has anyone ever said "Hey, ya got too many pictures." Never happened.

 

[Ralph Johnstone]

Could this be with a 3 pin sender which sends pressure signal and a 8 psi warn?

I have heard about a sensor which is both a pressure sender and a pressure switch. Happy Googling. Make sure everything matches you boat's wiring for the switch and the new temp. gauge which you will purchase.

 

[smokey73]

If you are concerned with the block modified by the PO you can probably replace the block with a more compact Tee as long as the block doesn't serve some other function. I'll post some pictures of what I did with my Yanmar later.

 

[Ralph Johnstone]

I'll post some pictures of what I did with my Yanmar later.

That's been my problem here. The PO has a Universal M 18 and I've got a Yanmar. Two different worlds.

I wish @Stu Jackson would let us know when he goes on vacation. No consideration at all.

 

[smokey73]

Not so much a Yanmar vs Universal engine issue. Just an example of how an adapter or T could replace the big, clunky "box" as you suggested

My adapter had one male BPT that fit into the location of the original pressure sensor. (ordered from McMaster Carr). Yanmar used BPT threads for the OEM sensor. The adapter had two NPT female connections. I put in the replacement (non-OEM) sensor with male NPT connection into the adapter. The matching electric oil pressure gauge was placed at the helm where the original oil pressure gauge was. I also atached a metal weave female NPT oil line hose into the other NPT female location. I then ran the oil pressure sensing line to a mechanical gauge I put in the engine compartment (it is there for reference to the electric gauge at the helm should I think I have a problem.) The poster could adapt the same concept hooking his adapter into the original location of the oil sensor which now has a hose that feeds the block.

 

[Ralph Johnstone]

Could very well be. All depends on just what's hidden in that Pandora's box. Unless it serves some unseen purpose, I would say it's got to go.

 

[smokey73]

Here are the pictures I promised. As @Ralph Johnstone noted, you need to find out all the things that the "mystery box" does, feeds from and feeds to. It may be straightforward to replace the box with a simple adapter if it only provides a way to connect to the electronic gauge sensor and some other gauge. Don't use and teflon tape or pipe sealant where the adapter screws into the block and where the electronic sensor screws into the adapter. It needs to be able to have a good ground to work properly. You'll also need to know the types of threaded fittings (NPT or BPT) and get the right kind of adapter. The connection with the teflon tape goes to the mechanical gauge in the engine compartment. All readings shown are at idle. Pressure goes up to about 60 psig on both gauges at about 3000 rpm.

 

[adamv]

Where is that gauge installed? It does not appear to be located on the standard instrument panel shown in the link from @kloudie1. Find that gauge and see if it has a solid line, not an electrical wire, feeding it.

If all of the above is correct and the pressure on the gauge behaves as you have stated (drops slowly from 45 to 20 pounds as the engine heats up) and drops to 0 when at idle after that and the buzzer comes on that indeed, it is most likely you have a REAL low oil pressure situation. Two different indications, one electrical and one mechanical gauge both say you have low pressure - Believe your indications.

Thanks yes i agree - it does feel like its a real pressure issue but being that the guages are clearly suspect and theres a chance that its solely a sensor issue of course i'll try adding manual sensor first such as you show - FYI the boat has a completely non standard panel with an oil guage and buzzer( with no RPM or hour meter :/ but yes i do intend to install). The thicker line people are suspecting is mechanical seems too flexible to be mechanical but i will confirm by removing the panel and inspecting the guage.

More background: Thinking back I cant help this relates to my second outing this year - somehow between my first day starting of the boat and the second, a lot of coolant had leaked out of (I now check this before every start of the engine). I ran the boat for 100 yards away the marina before spotting the temp guage was high (like, max) and the pressure guage had plummeted. The marina is in a ferry lane so i had no choice but idle back. The pressue read very low then and the engine just cut out when i changed to reverse - luckily we'd got a line to a bystander by then. When i nervously went to start the boat the next day i spotted the coolant issue but it seemed to start and run fine... perhaps until i next ran it for more than an hour at higher revs (i had run it a few times before this but dont remember an issue) when i noticed the pressure going lower. Now, I will say this... when you have an incident like this, its like a health scare. You tend to be hyper vigilant and end up with your eyes glued to the dials. Its entirely possible that the boat has always started at 45 psi and then drifted down to the 30s - after all its expected that as the viscocity reduces due to heat the pressure reduces a bit. It may be that the problem just got worse after the incident or has always been issue. I also should add that the oil level read about 40% at the time- still well above the minimum, but i understand that lower oil levels do result in lower readings.

Final point: lets say i replace the guages and relief valve and confirm that the pressure is indeed dropping when load is suddenly reduced when at temperature - is the next step taking off the timing case and checking / rebuilding the oil pump? And if thats all looking perfect, is it possible a gasket is perforated somewhere or the block is cracked etc? Someone mentioned rods and bearings but that sounds like the kind of thing only a full rebuild would address, isnt it?

 

[Ralph Johnstone]

@smokey73 . is your number one picture upside down ? Can't get my head around where we are. Do you have anything taken from farther back ?

Also, is your adapter the hex tube with a 1/8" NPT hole in the side ? Looks good but would look even better from further back.

 

[Ralph Johnstone]

but i understand that lower oil levels do result in lower readings.

Absolutely not. Don't know who you heard that from but stay away from them. Crazier than an outhouse rat. The only time oil level affects oil pressure when it's :

a) too low and the pump sucks air
b) too high and the pump sucks foam (air and oil).

The thicker line people are suspecting is mechanical seems too flexible to be mechanical

Mechanical means that oil under pressure is delivered to a mechanical pressure gauge in the engine panel as shown :

​

Any soft tubing will suffice. The one you show :

.......................... looks like 1/8" polyethylene pneumatic instrumentation tubing. Really bad choice in a hot environment. The softened tubing will release from the compression fitting.

Keep us informed and take lots of pictures of what's inside the mysterious box.

 

[smokey73]

@Ralph Johnstone No, picture 1 is not upside down. It is looking down from the front of the engine. Can't really take from much further away as "things" clutter the picture. The oil filter is just behind the fitting and is horizontal to the engine. The sump can be see in the center at the bottom of the picture.

Yes, the hex tube is the adapter bought from McMaster Carr. It has male BPT threads to fit into OEM connection on the Yanmar and then two 1/8" NPT female threaded locations for the aftermarket sensor and mechanical gauge connection. The replacement sensor is the shiny silver cylinder with the electrical connection. The 1/8" fitting with the teflon tape and metal reinforced hose is the hose to the mechanical gauge in picture 2. I liked to have the independent oil pressure confirmation of the mechanical gauge that I can refer to when I suspect there is question with the electrical gauge. It is a lot less subject to wire resistance or connection issues like a electrical sensor.

I agree that what looks like the instrument tubing is not a good choice. That is why I used metal reinforced metal hose that is often used for turbocharger oil supply tubing in race cars.

 

[Ralph Johnstone]

After dislocating my neck trying to figure why your electric pressure sensor is in a different position and why the oil filter is in the wrong position, I conclude your Hunter 40.5 does not have a Yanmar 2GM.

Moving right along here, yes, your arrangement is the best for two different points of presure sensing. As I mentioned in post #22, somewhere out there exists a sensor which acts as a pressure sensor for a readout and a pressure switch for an alarm. I'll find it later on or I won't be able to sleep tonight.

 

[Tally Ho]

View attachment 227436

I bet it is a fuel return line from some unknown banjo bolt

Greg

 

[adamv]

OKay so one line is the buzzer and the other is a mechanical tube - I can see the oil leading to the guage.
You can see replacing these guages and sealing the panel has been on my list for a while.
I'm going to spend some proper time on the boat at the weekend - it will then be in its home for the winter and I can safely open up the box, take measurements, clean up the ER and order the new guages.

I'm assuming switching to all electric would be better wouldn't it? I hate the idea of a flimsy tube carring oil half way across the boat.

 

[Ralph Johnstone]

I hate the idea of a flimsy tube carring oil half way across the boat.

As I said, that tube and its fittings are for compressed air, NOT at engine room temperatures, and up to approx. 50 PSI. You know the rest of the story.

If you are serious about your boat, I suggest bringing everything up to a reasonable level of reliability and preferably electric in operation. Then do some serious investigation into your low oil problem in the order I recommended in order to keep the price of the investigation as low as possible. That's all I've got.

OUT

 

[smokey73]

After dislocating my neck trying to figure why your electric pressure sensor is in a different position and why the oil filter is in the wrong position, I conclude your Hunter 40.5 does not have a Yanmar 2GM.

Moving right along here, yes, your arrangement is the best for two different points of pressure sensing. As I mentioned in post #22, somewhere out there exists a sensor which acts as a pressure sensor for a readout and a pressure switch for an alarm. I'll find it later on or I won't be able to sleep tonight.

Yes, it is a Yanmar 4JH2E. It is the principle of being able to use adapters to provide input to the sensor's you choose to have I was trying to illustrate.

I personally don't like like the idea of one single sensor providing two functions. I removes the concept of redundancy.

In fact I now have three separate measures of oil pressure now. Probably overkill but it was a simple mod. I now have one electronic sensed gauge reading pressure at the panel, one sensing pressure at the mechanical gauge in the engine compartment, and a third that is a "low pressure switch" sensed at a different point that provides an alarm if the pressure gets dangerously low (about 8 psi). Originally I was just going to install a temporary mechanical gauge to figure out why my electronic sensor was reading low, but it was just about as easy to make it permanent since I had to have an adapter anyway.

 

[Ralph Johnstone]

One last word ........................................

360-006 - VDO Sender Pressure 80PSI - 360-006 - VDO - automotive gauges - Vehicle Controls

360-006 - VDO Pressure Sender, Max. Pressure: 80 PSI / 5 bar, Voltage: 6-24V, Ground: Standard, Connection: Knurled Nut, Ohm Range: 10-180Ω, Thread: M10 x 1.0, Warning Contact Point: 7 PSI

vehiclecontrols.com

VDO offers an 80 PSI sender with 7 PSI low pressure alarm contact.

I personally don't like like the idea of one single sensor providing two functions. I removes the concept of redundancy.

Ordinarily I would agree with you. But this is VDO and pretty much bomb proof.

OUT

 

[smokey73]

Great find. I like VDO gear. The OP has some pretty good ideas for sorting out his issues and hopefully will first determine if he has an actual low pressure condition before he proceeds much further. I think he does but time will tell. I think we have about exhausted this subject too.
OUT

 

[adamv]

UPDATE!: ... fixed!

So turns out that @smokey73 and @Ralph Johnstone had good instincts that there were two issues at play here.. fortunately the fix wasnt to install a new relief valve or oil pump... it was a new thermostat!
Interestingly chatGPT suggested checking the thermostat - and I found temp didnt reach operating range in the expected time. I ran the engine for an hour and noted down the time, RPM, temperature and pressure at 5 min intervals. The engine took 40 mins to get to max temp which was only 135F while the pressure dropped from 45 to 25psi. Now, thinking back I remembered that when i had the boat on the hard last summer, we had to remove the thermostat housining and i had spotted that it had got slightly dented when i was trying to break off the manifold. The boat ran fine on the 35 min trip back to the marina so thought nothing of it.
Replaced it the other day and the engine temp got to 160F in 20 mins and the pressure remained at a happy 45PSI

As for 'pandoras box', as suggested above I ordered a VDO dual switch+sensor and guage to replace the JB welded box... so that should end the pesky leak and sketchy trip through hoses meant for air and not oil.

Thanks everyone for your help, my boat salutes you!