alarm sounds

[capercanuck]

The alarm on my 350 OMC sounded yesterday after running for approximately 30 minutes. The alarm I'm talking about is the one that tells you if the engine temp, transmission temp or oil pressure gets too high. At the time the engine temp had risen to 180 degrees...a stuck thermostat. The thermostat in it is a 160 degree unit. I took the thermostat out and the temperature dropped dramatically. The oil pressure was at 40 lbs...but when rpm increased the oil pressure increased. I guess this is normal. The alarm still sounded when the boat was running. I had to take my chances to get the boat back in, and it ran really well all the way back to the dock. The alarm sounded all the way in. The oil is full and clean. The belts are tight. There is was no thermostat in the engine, so it was running really cool. What is my next step? How can I track down the source of this problem? I don't know how to tell if the transmission is running hot. Is 40 lbs oil pressure sufficient? Any help is really appreciated!

 

[capercanuck]

Re: alarm sounds

anyone?

 

[starcrafter]

Re: alarm sounds

Not sure on an OMC, but check your lower unit lube level. My lube level was just a little low after winterizing and the alarm would not shut off until I put just a little more in. It would also go off intermittingly in rough water even though all fluids were topped off correctly.

 

[Boatin Bob]

Re: alarm sounds

You don't say what year it is or if it's a Cobra or not but on my 89 Cobra's there are 2 senders for the alarms, one for over temp and one for NO oil pressure, they both feed one alarm (they are just switches that have a single wire and ground it out when closed), it's possible one of these has failed giving you a false alarm. The no oil pressure switch actually should alarm when you turn the key on and start until the pressure builds up enough to turn it off, the over temp shouldn't go off until around 200 degrees. You'll have to find which one is alarming by process of elimination. The oil pressure switch is usually mounted on a tee with the oil pressure sending unit for the guage, the over temp is screwed into the block up near the front of the engine. Start the engine and pull the wire off one or the other until you find the bad one.

 

[capercanuck]

Re: alarm sounds

Thanks a bunch for the information. I have since disconnected the sender that is mounted on the thermostat housing. The alarm stopped. The sender appears cracked, so I'm not taking any chances and I ordered a new one. I just found it weird that it didn't show up in my manuals. I'm going to check out the oil pressure sender too.

 

[Boatin Bob]

Re: alarm sounds

These alarm switches were optional on the Cobra's I think but they came with all the King Cobra's. You could buy a kit from the dealer to install them afterward or you can buy aftermarket ones and that's why your manual probably doesn't mention them. I have an OMC factory manual and they are in there. I attaching a link to Doug Russells site which has on line parts blowups for OMC's. Just pick your year and engine size and then which section you want to see, you should be able to see all the sending units in there. Doug Russell Marine