Source of audible buzzer alarm?

[Capt. Rodbone]

Grand Banks 42 Classic..Twin Lehman 120’s and Berg Warner Velvet Drive Trannys
Late yesterday pulling into a transient slip dead downwind, two boat lengths to go and sun setting directly over my bow greatly limiting my visibility from the fly bridge, I have a buzzer start going off. First thought was I’d lost an engine. But quickly learned I had not. Think I recall looking at both oil pressure and water temp gauges but can’t be sure it all happened so fast. As soon as I learned I still had power we were entering the slip anyway. Once in the slip with a dockhand aspiring my wife with lines I went below. I think I noticed the lights on the drive train indicators on, but it could have been the glare coming straight in on the dash. I shut everything down. Within a few minutes I was below checking the fluid in both transmissions. That seemed fine. I decided to read up and learn what I could and deal with it this morning. As I was starting to do so my next slip neighbor was by his rail and as we talked he said he is a retired marine mechanic and was curious about any lights or audible alarms with a Velvet drive transmission because he’d worked on many and had never seen that. He came onboard and said that buzzer was likely something else and maybe it was the glare on the lights because the transmission shifts fine and sounds fine when I started it. I didn’t check the fluid in it yesterday afternoon because I understand it you should do so immediately after shut down? If so, now I’m wondering if it reaches operating temperature just in the slip? Thinking maybe we leave the slip and just stay close by and shift in and out and let all systems get to operating temperatures and see what happens. Interestingly, I am reading in the manual on a troubleshooting chart that says regulator valve buzz. Could that be what I was hearing? If so, it says two possible causes are low oil level and regulator valve, stuck so polish it with crocus cloth to remove burrs and clean. Could that be what I was hearing, and if so, how could a mechanic who has worked on many of these not know about an audible or light alarm? just looking for guidance on how I should proceed to make sure I don’t have an issue. Mostly, I suppose how do you suggest I prep the transmissions to make certain I have the proper level of fluids in each?

 

[PM]

If you throttle back rather abruptly it can result in temporary low oil pressure. Do you hear the same buzzer when you turn on the key before you start the engine?

pete

 

[Choices]

On my VD the only alarm is at overtemp around 190. Easy test is to pull rubber boots off sensor and use screw driver to short terminals.
See if the buzzer sound is same. The other sensor is neutral lockout switch.

Mine was overheating do to an error during the rebuild by a BW expert. Was fixed under warranty.

Overtemp is not a problem till around 210. Check tranny cooler for blockage. Then check all the coolers and water flow out exhaust.

Also look at wiring diagram and see what else could be connected to buzzer.

As a side note my GB alarm panel was wired wrong from the factory and four owners and no telling how many surveyors missed it. I found it cause of a tranny overtemp. I had an alarm, but no indication of why.

Go to my blog, grandbankschoices, and you can dig around and read about it and a bunch of GB fixes.

Any questions PM me.

 

[Capt. Rodbone]

Thanks to each of you for your reply. We just had it happen again, so Pete, I think you’re on to something. As we were coming into a marina slip just now it happened again as it did two dockings ago at a different facility. This time I was able to determine that yes it is the same buzzer as when I start the engines, and I was able to notice that the oil pressure on the port engine dropped to zero thus the buzzer. Shut the engine down and once securely in the dock, I can’t re-create that. Oil pressure returns to normal. Not sure this thought has any relevance, but each time we had not been in reverse for at least five hours. If I started being conscious of that, and made sure we did a bit of low rpm shifting before attempting to come to the dock could that possibly help?

 

[Comodave]

Check all the connections in the alarm circuit and clean them up. Could be a loose or dirty connection. Maybe swap the wires on the oil pressure alarm senders with the other engine to see if it is a gauge problem or an actual low oil pressure. If the gauges check out put a mechanical oil pressure gauge on the engine and see what it reads when the alarm comes on.

 

[High Wire]

Buzzer AND pressure gauge reading zero? Two almost independent indicators of the same parameter. Could be an actual condition. The rule of thumb for instrumentation is believe your indications until proven false.

 

[Jeff F]

Buzzer AND pressure gauge reading zero? Two almost independent indicators of the same parameter. Could be an actual condition. The rule of thumb for instrumentation is believe your indications until proven false.

That's what I'm thinking. Is the oil level correct? Any signs of diesel in the oil?

I don't understand the transmission concern. Seems like an oil pressure alarm, which should be taken seriously.

 

[Choices]

To test oil prs gauge you can push start and stop buttons simultaneously, and as engine spins up watch gauge and listen to buzzer. Having second person recording both with phone would be great. It should not start, but prs. should go up.

Confirm oil on stick before and after very quickly, in seconds. Might have hatch open and ready.

Let us know what you find out.

Don't crank on it long.

 

[Choices]

Confirm we are talking engine oil. Tranny lube oil light is over temp.

 

[OldDan1943]

Chances are, you will not have trans oil pressure unless the trans is in gear and a few RPMs. (Read that somewhere on the forum.)
What I want is separate indicator lights for the alarm condition, to help sort things out. Plus silent switches so as to not destroy the helmsman’s hearing and distracting beyond necessity

 

[Choices]

There is no lube prs switch on VD I am aware of. You can add one, and a gauge.

The oil pump on tranny is driven if the engine is running. I am thinking if tranny fluid is low it might not go into gear, or fall out of gear. Would run hot if not enough oil to cool.

 

[slowgoesit]

Given the potential damage to the running gear if your engine oil pressure IS going to zero, I think I would temporarily hook up a standalone engine oil pressure gauge to verify whether or not your instruments and buzzer are correct or not. Assuming everything is okay without further investigation could end up to be pretty pricey!

 

[Capt. Rodbone]

My original concern about the tranny in this thread has been ruled out. Yesterday‘s alarm going off again as entering a slip allowed me to make sure I scanned gauges and that’s when I saw the reading of zero on the port engine and the buzzer going until I shut the port engine down. I’m going to try what “ Choices’ suggested a couple of posts ago when I can have my wife ready with her camera and I will let everyone know the result
Thanks to all of you again

 

[PM]

Could be as simple as low oil, have you checked?

pete

 

[C lectric]

Are you going to install an independent mechanical pressure guage? It will need to be of about a 500 to 600PSI range. Many gears operate in the 300PSI to 450 PSI range.

For an engine typically a range of about 100PSI or maybe 125 PSI will be enough.

You should find out from an independent guage if the alarm is serious. Other wise you risk damaging the gearbox or engine.


Low oil or pressure in a gearbox could allow clutch damage which will cost far more than a guage and a few fittings. Same goes for the engine.

And as asked have you checked the oil level according to the manual? Most require the engine to run so all the external hoses and the oil cooler is full.

 

[Choices]

I would
1) compare dipsticks
2) spin engine without starting to check for oil prs cold. Spin good engine 1st to time roughly how long to go. Mine cold takes awhile, seems like forever, probably 5 seconds. If boat has sat a month I do this until prs then release the stop button with oil prs.
3) when was last time oil was changed?

Oil pumps just don't fail fast, typically a slow death that causes something else to break first.

 

[SoWhat]

VD transmissions are not equipped with any alarms. There is a spare port on top that can be used for either pressure or temp. Temp probably has more value.

Lehmans typically have wired oil pressure alarm and separate gauge circuit, and water temp alarm with separate temp circuit. The sending units are inexpensive and easy to replace. Note that oil pressure alarm is tied to alternator so it won;t produce current until there is oil pressure.

I would start with oil pressure gauges and make sure they are both registering expected numbers. Switch leads and repeat.

Then move to senders. If you can't replicate alarm at dock, and pressures are good, then I would proactively install new alarm sender.
They can fail and connections can become corroded. Take some emery cloth and ensure all connections are bright brass.

Replacement oil pressure gauges are also inexpensive if just for diagnostic purposes. I bought a cheap gauge and put it on top of the dash with 2 temp wires to sender,

 

[Choices]

What did your testing show? I am interested in the out come. Might happen to me someday...

 

[Capt. Rodbone]

Update from OP me

To answer some of the questions in earlier replies first.
1. Oil and filter change on both engines about 25 engine hours ago.
2. Oil levels are checked every day before I start her. Probably not related but this engine DOES USE/LEAK about 8 ounces every 10 hours.
3. Had note previously noticed but the pressure gauge for this engine stays at 20 even when off. We noticed this when we did what “Choices” recommended by watching and filming while pressing both start and stop buttons. Pressure did however start it’s way up then. Probably need to do same experiment from fly bridge.
4. Once doesn’t mean celebrate I’ve solved this, but given each time it happened we were coming into a slip after 5 to 6 hours running, and reverse hadn’t been used, yesterday rather than come straight in, I idled down and then at minimum RPM’S did a few shifts with each engine. Glad I did once I rounded the outside dock with view of where they wanted me being blocked by a small cruise ship on the outside dock. I had to turn our 42 ft 180 degrees in about 80 ft with about 2 knots of current and a starboard tie in about 60 ft of dock space. Two deckhands there new what they were doing though and it went off without a hitch..likely would have even with a loud buzzer ringing the last two minutes, but it’s great to avoid that. Cruise ship was then my ally, as it completely block about 15 knots of what would have been a beam wind.
Then, in “me fashion” as soon as we were secure and shut down, I was pissed this large 3 deck ship was blocking mt breeze!?

About to post a new thread on my newest challenge, so standby.

 

[High Wire]

If your oil temperature is too high the oil pressure will drop down to the alarm point when brought down to idle from a good run. Check your oil cooler performance.
On an old boat of mine the oil pressure went UP when hot. One day the alarm sounded after a run with the pressure gauge reading 75#. Turns out the VDO gauges went to Teleflex senders on the Crusader engines from the factory. Complete mismatch!