Mk II oil pressure alarm

[Stu Jackson]

I am 95% certain that the fuel pump only runs when the key is turned and held in the solenoid position. It does not run when initially turning the key to first position, or when returning to first position after heating the glow plugs. However, the buzzer does continue when returning to first position, so I guess it's possible the pump continues to run but I can't hear it.>>>>>>>>>>>>>>>>>
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It sounds like I should just replace the key switch, and that should fix the problem. (I know you don't like the wiring scheme, but changing that is above my pay grade.) I'll try shooting some contact cleaner in there first just to try. Is there a good substitute part, or should I just order the genuine Westerbeke key switch?

The Critical Upgrades topic discusses how this works in great detail.

Key switch covered in my recent Mainsheet article: 

http://c34.org/Ignition-Key-Switch-Replacement/

This is for a Mark I which only requires an I/O switch, not three position.

[KWKloeber]

Breakin

Of course there's no 100% guarantee that it's the switch but it's cheap insurance to replace it. Myself, I'd troubleshoot to convince my brain that it's the problem, but it all depends on time/ability.

Defender carries C-H ignition switches. From what you describe you have a 3 position.
OFF - ON - MOMENTARY ON
(off / ignition / start)
Panels that have both start and preheat push buttons use the 2 position (OFF - ON) switch.

Get the rubber weather cap for it if the part Defendet has doesn't already include it. Some C-H part numbers include the cap.

[Breakin Away]

Wait.  Wb switch?  Does your engine have a Universal panel or a Seaward panel?
The Seaward panel doesn't have a Wb switch in it.

My boat has the panel at the binnacle under the wheel, typical of MkII boats of my vintage. I don't recall whether it's made by Universal or Seaward - I'll have to check next time I'm there.

I definitely want a switch that comes with a rubber cap (or accommodates one purchased separately). With the key switch at the helm, that seems prudent.

[KWKloeber]

My boat has the panel at the binnacle under the wheel, typical of MkII boats of my vintage.

Oops didn't notice the mk-ii. DUH

It's a Seaward panel, no Westerbeke part number.


Cole Hersee M-550 Marine Ignition Switch
https://www.defender.com/product3.jsp?id=917256

Item # 204594
(3) Positions: Off - Ignition - Ignition / Start
Ignition / Run: 10 Amps @ 12 Volt DC, (3) Brass Screw Terminals
Key Removable Only in Off Position, Spring Return to Ignition
Model Number: M-550 BP



Cole Hersee 83288-BP Ignition Rubber Boot Nut
https://www.defender.com/product.jsp?id=917192

Item # 202098
Chrome-Plated Brass
Self-Closing Rubber Key Slot, Weather Resistant
13/16" - 24 thread
Model Number: 83288-BP

[KWKloeber]

Does the switch/alarm ALWAYS act as you describe? 

ie, after you flip back from preheat (alarm sounds,) then turn key off and back on - does the alarm sound or not sound?
    - If it's loud I'd initially suspect the ignition switch (messing with the contacts temporarily makes it work)
   
To convince myself whether it's the switch, I would:
     - Carefully pull my panel; not disturbing any switches, wires, etc
     - With a short wire, touch the ignition switch B terminal (heavy red wire) and I terminal (don't know the color but it should be marked.) 
     - If the alarm is loud, I would suspect that the switch is bad.

[John Langford]

I installed a new oil pressure alarm switch over the weekend. It turned out to be not nearly as difficult as I anticipated. The key is removing the front wooden panel on the engine compartment. I then could get a box wrench on the nut used to tighten or loosen the oil pressure sender. Once it was out of the way, I could get large adjustable pliers on the body of the alarm switch and break it loose. I tidied up the small amount of oil that leaked out, installed the new switch and then the old sender, attached the wires to both units and tested the engine.

Unfortunately the new alarm switch didn't make much difference. The oil pressure gauge works fine, but the alarm buzzer still does not sound when the engine key switch is turned to the first position. When the key is turned further just briefly to engage the solenoid and glow plugs, and then returned to the first position, the alarm buzzer sounds. It does not sound after the engine is shut down and the key is left in the first position. I have no idea if the alarm will sound if I lose oil pressure underway. I suspect not.

Ah well, at least with Ken's help  I now know how the alarm system works and I feel more confident about dealing with its various components. I will improve the wiring at the oil switch terminal as Ken recommended and then lick my wounds...literally, as the wrench work in very tight quarters is not easy easy on the old bod.

[KWKloeber]

John

I'll give this some more noodlin. 

At least your results squares with my analysis that "it's not the oil sw itself."  Whatever consolation that bring I dunno.

Humor me, it's been a while...  bypassing your key switch did not help, correct?
I'm still thinking - power resistor or preheat solenoid issue, but that's w/o studying the schematic once again.

[Roc]

John
My alarm does the same thing. Been like that for almost 20 years.  Not always, but sometimes at the first position, no alarm.  Move key up to engage glow plugs, then back down, and alarm sounds.  Sometimes alarm sounds at first position as it should.  Sometimes I need to engage glow plug position more than once and alarm will sound in first position.  It's just random.  Sometimes when engine is shut down, alarm sounds, sometimes it doesn't.....  Also, sometimes when running in gear at low RPM (~1200 or so), alarm chirps.  Increase RPM, chirp goes away.

[Jim Hardesty]

Gentlemen,
Shamrock's alarm always sounds when there is no oil pressure, except when the glow plugs are on.  Never a chirp.  I must have got a very good ignition switch.  On my wish list for the perfect boat would be an oil pressure gage along with the alarm.
I only wanted to report my experience.  Not saying there's anything wrong with the way other boats are.
Jim

[Breakin Away]

As previously reported, my boat has the same behavior as John and Roc. I wonder if Catalina changed components/design between #1535 and #1570.