Continous Alarm

[J Vaughan]

I have 1995 Merc 135hp with a continous alarm problem.The book says that it is an overheating alarm.Also,there is no water coming out of pee hole at idle speed but it does come out at mid rpm's.The alarm goes off as soon as I put boat in water (while it is still "cold").Can someone tell me if this is a cooling problem or do I have an alarm problem?Any and all suggestions on how to fix this problem would be appreciated.

 

[wyattm]

Re: Continous Alarm

It sounds like a water pump problem, I had twin 200 mercurys and when the impeller went bad, it would alarm at idle or low speeds, when you run the impeller picks up more water and the engine cools. If it's not peeing I would run a coat hanger up pee tube to make sure it is clear spiders, insects or dirt.<br />I would also change thermostat if it hasn't been changed recently. I would not run the engine until the problem is resolved. If the alarm is steady it is a water cooling problem, if warning horn is interment it is an oil problem if you 135 is set up like a 200. Good luck.

 

[J Vaughan]

Re: Continous Alarm

Changed impellar and also took thermostats out and put them in water on stove top and watched them open and close several times but still getting continuous alarm.Thought it may be an oil problem but the motor smokes when started as it has always done.Any suggestions on what to do now.Thanks.

 

[clanton]

Re: Continous Alarm

The stats start to open at 140 degrees F. Continuous alarm, overheat condition, overheat sensor, or warning module. You check the thermostats by heating water till stat opens insert a thread between valve and body, let valve close against thread, suspend stat from thread in water, heat water 140 F stat should drop off thread. You need to check engine temp with melt stick, temp gun, probe. check behind thermostat housing.

 

[J Vaughan]

Re: Continous Alarm

I unhooked the overheat sensor and the alarm still sounds.There is another wire (tan w/blue stripe) coming from a black box that hooks to the same post on the motor.If I unhook this wire then my alarm stops.I assume that the black box is the oil injection module so this is telling me that it is an oil problem and not an overheating problem.Can someone verify that this is correct or not?

 

[taylormd]

Re: Continous Alarm

I have twin 1996 Merc offshore 150s that are carberated. Recently, my oil alarm went on my port engine. The oil sensing unit was bad. I had it replaced and the alarm went off. I was fairly sure the engine was oiling because of the smoke. However, I am sure that if I disconnected the alarm, a real oiling problem would "pop-up" and I would burn the engine up. <br /><br />One other thing, the dealer advised me to replace the check valves in the fuel line. If these become clogged, the oil pump can be damaged and then there are real problems. I had never done this and the dealer said they should be changed ever couple of years to be on the safe side. The check valves are cheap and you can do them yourself.

 

[clanton]

Re: Continous Alarm

The black box is is for oil and overheat. The box is part of the problem.

 

[J Vaughan]

Re: Continous Alarm

Thanks to all that replied.<br />I have checked thermostats and head temp with thermometer and they are good.I know I am getting oil by the smoke when starting engine.Now I am curiuos about the sending unit mounted above oil pump.It has 3 wires coming out of it (white,black,and blue w/white stripe)what is this for?Anyway I unhooked the white and blue w/stripe and my alarm still sounds.Also unhooked blue wire going to the cap and still get an alarm.If I unhook tan w/blue stripe wire going to the box the alarm goes away but then I dont get the beeps when I turn the ign.switch on so what should I do? Getting oil,not running hot,but also getting alarm.Also,about how much will the black box cost if I have to replace?

 

[clanton]

Re: Continous Alarm

Motion sensor test. Disconnect white wire from module , module white wire voltage should be 12+- 1 volt. Voltage ok reconnect white wire. All wires connected check output voltage from blue/white sensor lead, remove sparkplugs ground leads, ignition on, use emergency start rope and rotate flywheel, voltage should peak a 5+- 1 volts then drop to 1 volt every 2 revolutions of the engine, if no voltage, sensor is bad or oil pump not turning. From Merc manual.<br /><br />Overheat sensor, disconnect overheat sensor turn key on, if horn sounds cointinuous, warning module is bad, replace module and retest, if horn does not sound overheat sensor is bad.