Yanmar 'Diesel Preheat'

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Ductboy

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Last weekend I blew the hose leading from my heat exchanger to the gear cooler. This happened just before I returned to my slip. Just before I realized this issue, the 'Diesel Preheat' light came on on the instrument cluster.

I changed out the hose no problem, but the light is staying on.

That light normally comes on and goes off at start-up. Now it does that, but after about a minute of running in the slip, it comes back on and stays on

The engines do not have glow plugs (as far as I know), so there is no actual preheat associated with these motors (6LY-STP 350hp)

I'm thinking it may be a short in the Yanmar instrument cluster, but I'm looking for any possible ideas. If it was a short, I think it would come on and stay on at start up, not disappear and come back on after it had run for a minute or two.

Thanks

Dan
 
If it's a twin engine boat you could switch instruments from engine to engine and see if the fault switches. I'm pretty sure the 6LY has glow plugs.
 
Thanks for the reply, that's a good idea, I'll give it a try.

Dan
 
The light being the first indication of something wrong leads me to think water was spraying on something related to that warning before you noticed the hose was blown. Look for wires or connectors nearby.
 
One thought would be to call a Yanmar dealer or shop and ask them.
 
quote:
Originally posted by rawidman

One thought would be to call a Yanmar dealer or shop and ask them.

Click to expand...


I was always able to get very good information from Mastry Engine Center in St. Petersburg, FL. Call and talk to their service department.

Bob
 
Ran the engine today while I had the local Yanmar dealer on the phone. He didn't have any definitive reason for the light to come on, but he didn't think that these motors have the preheat option. As we spoke and the light had come on, after about 5 minutes at idle, the light went off and did not return. I think I'm in agreement with pdecat about water from the burst hose possibly getting into the wiring connection. Once it dried, it went off (hopefully for good).

Next problem...

While I was running the engine at idle, I noticed that the port engine (the one I replaced the hose on) had low oil pressure at idle. The needle hovers just in and out of the red area (around 20psi). The stbd engine shows 40 psi at idle. When I run the engine up to 1500 rpm, the gauge moves up to 40psi no problem (which is where the stbd engine is at for 1500rpm)

I've heard about Yanmar having trouble with sending units.

I'm scheduled to bring the boat to the local Yanmar guy in a week, but am interested if anyone has any thoughts or suggestions
 
If one connector is wet, it is likely two got wet.
 
Open, clean and lube any connector. CK for any corrosion on the oil sender wiring. Quite possible both problems are the same, salt water corrosion.

Check oil level if it is high you might have diesel in the oil. Feel the oil on both engines and see if one feels very thin.
 
Salt water electrical problems generally don't go away just because they dry. They usually get worse unless you stop the corrosion. I agree with Bruce open and clean any connectors and the connection to the oil pressure sender unit with a lube anti corrosive electronics spray.
Bill
 
Agree with with your thoughts on the problem not going away. Luckily, the hose that broke, evidentially did so, just before we returned to our marina. There is a a short stretch where we can run fast, which I did. There was no water in the bilge and there was no water pumping prior to that. That area of he river is all fresh (about 4 miles up from the sound).

Any water that did come in leaked from the hose down into the bilge, which is away from any wiring harness.

I will check/clean/lube the connections to the sending unit.

Thanks all for the advice

Dan
 
quote:
Originally posted by Ductboy

...........Next problem...
While I was running the engine at idle, I noticed that the port engine (the one I replaced the hose on) had low oil pressure at idle. The needle hovers just in and out of the red area (around 20psi). The stbd engine shows 40 psi at idle. When I run the engine up to 1500 rpm, the gauge moves up to 40psi no problem (which is where the stbd engine is at for 1500rpm)

I've heard about Yanmar having trouble with sending units.
Click to expand...


If you suspect the senders, it's pretty simple to swap them between the engines to see if the problem is with the sender.
 
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