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What does the 3-position switch on my J35 do?

Tyson0317

New member
I recently bought a J-Boats J35 which came with the original Yanmar 3YM30 and a freshwater heat exchanger. I have 2 questions:

1. The console (where you put the key in etc.) has a 3-position electrical toggle switch. When flipped up, the "C.W.Temp" light immediately comes on. The middle position does nothing (with the light off). When flipped down it also doesn't seem to do anything. I crawled behind the console and I can see wires connected to all terminals, but I cannot figure out where they go to. I tried flipping the switch in all positions to hear for noise of a relay and I don't hear anything. I assume that C.W.Temp is Coolant Water Temp and having the light on is a bad thing. I have been running the engine/boat with the switch in the middle position and everything seems fine, but I would like to know what this switch does and why it is there...

2. Can someone give me a definitive answer on whether this engine has a built-in glow-plug or other pre-heat device? In the Seattle winter weather (40's F) the engine is VERY hard to start and I was concerned about burning out the starter and/or damaging the batteries. It would also send a good amount of raw diesel into the water via the exhaust, which I am not happy about. Once it runs for a bit and warms up, it fires right up with barely a chirp of the starter. I have since read various techniques for starting diesels of this class ranging with everything from pouring boiling water on them, to pointing space heaters at them, also apparently there is a method to start which involves flipping a decompression lever before turning the engine over (I guess to let warmer air in), also people seem to use starting fluid. I rigged up a hair dryer in my engine bay which after running for ~10min makes a big difference for me... That said, is there a glow-plug on this thing that I am not seeing? Is it possible to add glow plugs? I own two newer diesel cars and never had starting problems. Would be nice if my boat started without fuss or needing 110 shore power.
 
You should already have Glow plugs in that engine. You may have to turn the key switch to the left and hold it for 10 seconds and then back to start. Take a picture of your panel and post it so we can see which one you have.
 
So Im going to the boat tomorrow and I was going to snap a pic for you guys since almost an hour on google image search I could not find a control panel like mine. Then someone suggested to use Bing and there it was on the first page. This apparently from a Hunter boat, but aside from the clear cover, this is exactly the console that I have!

YanmarCP.JPG

You can clearly see the rubber 3-position switch between the speaker and key hole, above the starter button.

Now, does anyone have any idea WTF this is??
 
The switch is to test the warning lights and the warning alarm. I found this wiring diagram and ID list on another site. Check the key switch again, How many positions does it have? Check one more time to see if it is capable of turning to the left and springing back to off. According to the diagram, your key switch activates the glow plugs for preheat turning to the left and also heats the plugs while cranking. I would check the glow plug relay operation and amperage draw from the plugs themselves. Might be as simple as worn out glow plugs.

1 – Alarm Lamps
2 – Buzzer Oil Pressure
3 – Coolant Temperature
4 – Sail Drive Seal
5 –Charge
6 – Fuse (3A)
7 – Stop Switch
8 – Diodes
9 –Key Switch
10 – Tachometer Hour Meter
11 – Instrument Panel
12 –Wire Harness Option L=3M
13 –Wire Harness Option L=6M
14 –Amplifier Only for Sail Drive
15 –Procured by Customer
16–Battery
17–Battery Switch
18 –Engine Stop Solenoid
19 –Relay
20 –Glow Plug
21–Stop Relay
22–Starter Relay
23–Starter
24 –Coolant Temperature Switch
25 –Engine Oil Pressure Switch
26–Alternator
27 –Ground
28 –Sail Drive (only for sail drive)
29 –Key Switch
30 –Coupler (view from A-A)
 

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Chris, you are AWESOME!! Thanks!

So given that only the CWTemp turns on, that means my other bulbs are dead? And given that the buzzer doesnt sound, that means its dead too? Good to know!

That said, I was on the boat today (before reading this last reply) and I did try turning key left - it didnt go. Lock only has 2 positions - on and off. I tried pushing it a fair bit. The key is old and I didnt want to snap it in the lock.

Pardon the stupid question, but can someone show me what glow plugs look like on the engine? I lifted the cover a few times - saw the injectors but didnt see any plugs. Im planning to do an oil change next weekend, so I will have everything very open. Somehow I think that there just isnt any glow plugs on this motor. Today I did the hair dryer heating for only 8 minutes today and left a big slick on the water when cranking for a long time and starting. If my engine doesnt have plugs, can they be retrofired?
 
Seeing that this is an older model, it does not have glow plugs or provisions to install glow plugs. Actually this engine does not need glow plugs as it should fire on compression alone on the coldest days.

After changing the fuel filters and purging the fuel system, I would disconnect the exhaust to eliminate a possible exhaust clog (too much back pressure in exhaust will cause hard starting) and extended cranking will result in water inversion(While testing).

If no clog is found, I would move on to a compression test.

Has starting fluid ever been used in this engine? Starting fluid will cause immediate damage to the ring lands on the pistons, causing loss of compression and hard starting.
 
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Ive never used starting fluid and I did not find any aboard when I bought the boat. But its from '89, so who knows? That said, once I get it running and it warms up, I can start it with barely a chirp of the starter hours after the engine was shut down.

After going out a few times I got concerned that the fuel gauge always showed Full. Thinking that it may be broken, I went to the fuel dock to fill her up and she only took in 2.5 gallons - I was shocked at how little fuel it uses! With that, it is quite likely that the fuel in there is likely old.

I still need to figure out where the fuel filter is - that's on my maintenance list along with oil and filter. I also want to find the coolant intake trap. My engine has a heat exchanger, but I was told that the seawater coming in has a filter/trap on it to catch any seaweed/junk and I have no idea what might be in it or where it is...

Also, for what I have read, cold starting problems are common on these engines in these temperatures. Ive read about people pouring boiling water on the engine to warm it up. Also opening the decompression ports to let the relatively warmer cabin air into the cylidners... Not so?? It should just cold-start without anything???
 
If everything is functioning as it should and the compression is where it should be, yes it should start on a cold day. Not -35F cold but a reasonably cold day.

Have a compression test done.
 
Chirs,

First, how does one test compression on this kind of engine? I've done gasoline engines through the spark plug hole more times than I can count, but never on a diesel. I assume I will need a bigger gauge too! Any idea what the compression should be at? Also, does it make sense to do a lead-down test? I got an FAA spec leak-down tester.

Per the 3-position switch: I messed with mine and it is not a test switch. Or it was re-wired for another function. I tested a bunch of the lights on my panel manually - they lit up. The switch illuminates only the C.W.Temp light.
 
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