Hi all: This is my first post on Boatered. We have a 2007 Bayliner 325 with 250 HP carbureted 350 engines. Our starboard engine alarm comes and goes at random. Usually while powering-up, cruising at 3500RPM, or slowing down from cruising. The alarms started when the boat was about 3 years old. The alarm beeps are sometimes short and sometimes longer, with no pattern. The carb engine setup has no computer and only oil pressure, overheat, or I/O drive oil level will cause an alarm. Of course everything is just fine and engine temps since new are 175 degrees at cruise. Oil pressure is fine, and the I/O drive oil resivours are full and disconected electricly. I suspect a loose connection at some point in the wireing. Some have suggested that I check the knock sensor. Anyone with suggestions is more than welcome to chime in! Thanks, griff4
Annoying intermittent engine alarm
- Thread starter griff4
- Start date
Yo! Griff! Welcome to Boater Ed!!!
Where in FL are you?
You already know about the oil level sensor on the outdrive reserve lube tank. Those 350's have the Low Oil Pressure Sender (NOT low oil level, checking that is up do you, the old dipstick way) on the lower Port side of the engines. Near where an Oil Filter would be if you don't have Remote Filters. Then I think your Thermostat Housing has two more senders, one for the Over Temp alarm. Suggest you start by making sure all those connections are clean and tight.
Where in FL are you?
You already know about the oil level sensor on the outdrive reserve lube tank. Those 350's have the Low Oil Pressure Sender (NOT low oil level, checking that is up do you, the old dipstick way) on the lower Port side of the engines. Near where an Oil Filter would be if you don't have Remote Filters. Then I think your Thermostat Housing has two more senders, one for the Over Temp alarm. Suggest you start by making sure all those connections are clean and tight.
- Joined
- Jan 1, 2000
- RO Number
- 385
- Messages
- 2,884
I had this problem a while back, amazingly it was a loose connection on the starter solenoid where the engine harness takes its power. The Mercruiser manual calls this "general condition check". Start with your battery terminal and follow the voltage all the way throughout the circuit. Also, don't forget the grounds!
Your carbed engine doesn't employ a knock sensor, does it?.
GeeBee's suggestion is interesting. If that doesn't do it, here are a few add'l suggestions:
You could try to disconnect and isolate one alarm switch wire connection at a time to see if the alarm disappears. But I would also look very carefully for a chafed (or loose) wire going to the OP, temp or I/O level alarm switches that may be intermittently shorting to ground. That might be found with engine off /key to ON and wiggling engine harness wires- if no luck, try with engine running.
Moisture in a harness plug is another remote possibility.
You could also try swapping OP and other alarm switches 1 at a time with the port engine. Just don't confuse gauge senders with the alarm switches which may be nearby.
Note I gather some Mercs and maybe other makes will sound an intermittent beep or two as a scheduled maintenance reminder and that alert will not go away until cleared. But the randomness you describe sounds more like a short.
GeeBee's suggestion is interesting. If that doesn't do it, here are a few add'l suggestions:
You could try to disconnect and isolate one alarm switch wire connection at a time to see if the alarm disappears. But I would also look very carefully for a chafed (or loose) wire going to the OP, temp or I/O level alarm switches that may be intermittently shorting to ground. That might be found with engine off /key to ON and wiggling engine harness wires- if no luck, try with engine running.
Moisture in a harness plug is another remote possibility.
You could also try swapping OP and other alarm switches 1 at a time with the port engine. Just don't confuse gauge senders with the alarm switches which may be nearby.
Note I gather some Mercs and maybe other makes will sound an intermittent beep or two as a scheduled maintenance reminder and that alert will not go away until cleared. But the randomness you describe sounds more like a short.
You didn't mention the engine brand. If Mercruiser, you certainly do have an engine computer. It is attached to the port exhaust elbow. The knock sensor is located on the starboard side under the exhaust manifold right off of one of the blue drain plugs. You also have one or two temp senders, likely off of the thermostat housing. You already found the oil sender. You may also have a transmission oil temp sender. You also have a couple of sensor wires going to the distributor and a capped off wire for putting the timing into base mode.
I had the same problem until this past year. In my case it was temperature related and changing the exhaust elbows corrected it. My temp was still between 165-175. The problem is that the temp gauge sender is cooler then the alarm temp sender, so you are fooled into thinking the temp is fine when it is not. But it certainly doesn't cost you anything to check all your wires first. You might also want to pickup an entry-level laser heat sensor gun at Harbor Freight. I got one for under $50 and it helped determine the temperature of the port and starboard side manifolds.
I had the same problem until this past year. In my case it was temperature related and changing the exhaust elbows corrected it. My temp was still between 165-175. The problem is that the temp gauge sender is cooler then the alarm temp sender, so you are fooled into thinking the temp is fine when it is not. But it certainly doesn't cost you anything to check all your wires first. You might also want to pickup an entry-level laser heat sensor gun at Harbor Freight. I got one for under $50 and it helped determine the temperature of the port and starboard side manifolds.
Check all the wiring as GB says. Your symptoms are indeed when extra cooling is required. Does the starboard engine ehaust sound louder than port? Reduced raw water flow would cause that. Sensors do indeed go bad most are cheap and easy to replace. Does the oil or temp gauge flicker?
Thanks so much for such a quick response by all. We are at Saint Pete Beach. I have changed the engine temp alarm switch and the Oil press alarm switch near the oil filter. The alarm switch near the distributor has been unplugged and the intermittent alarm persists. By unplugging the temp alarm switch (which has been replaced) the alarm no longer sounds. The exhaust manifolds remain warm when cruising, but are easily touched. The bravo II drive oil resivoirs have been unplugged. I will start by checking electrical connections all over the place. This boat is bone stock and the alarm started after 3 years, Does anyone know how to unplug the Knock sensor? It seems to have a "trick" connection and I sure don't want to break anything. Will keep you all posted. griff4
Sensor terminal looks like this:
And connector looks like this:
The plastic teeth in the small side connector click over the tapered edge of the sensor. Squeeze the large side and they release.
You can see more on Amazon using "mercruiser knock sensor" and it'll show you several MerC versions of the sensor, then where "mercruiser" is crossed off, the sensor and terminals I pictured. If you select the Knock Sensor Harness you can see the small side with the teeth and the large side to squeeze.
And connector looks like this:
The plastic teeth in the small side connector click over the tapered edge of the sensor. Squeeze the large side and they release.
You can see more on Amazon using "mercruiser knock sensor" and it'll show you several MerC versions of the sensor, then where "mercruiser" is crossed off, the sensor and terminals I pictured. If you select the Knock Sensor Harness you can see the small side with the teeth and the large side to squeeze.
Update on the annoying alarm. You guys may have pointed me in the right direction. Upon disconnecting the knock sensor, I took a short test run in our Intracoastal waterway. That darn alarm was silent! Ordered a Knock sensor and maybe I'll be alarm free for a while. And it was chilly today..50 degrees with a stiff east wind. Thanks for your assist. griff4
- Joined
- Jan 20, 2002
- RO Number
- 7269
- Messages
- 802
So glad to hear my army was able to help diagnose your problem. We have such a vast amount of knowledge on this board and it so heart warming when they can provide information to help solve a chronic problem. Welcome to the forum!!!!
Thanks to all you boatered members for your expert advice. In this annoying intermittent alarm problem, the darn knock sensor was the culprit! A new knock sensor has made us alarm free. I'm not even going to attempt to explain why, but it did the trick. The best to all, Griff4