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SOUTHERN CROSS

mercruiser,audio warning system keeps sounding

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my mercruiser twin is equipped with  an Audio warning System. The buzzer sounds when the key is turned on and is supposed to stop when the engine starts. 

The mercruiser manual says it indicates l.1. low oil pressure. 2. high tempeture 3. low drive lubricant.  All three are ok. 

where is the alarm located and what else should i be considering.  Everything else runs good except for the high screeching buzzer. 

Thanks in advance. 

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Un-plug the lead wire to the drive lube bottle. See if that eliminates it. If so, you need a new one.

They get gummed up and do not work after time, even though the lube is full.

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should I try both lead wires (2 bottles) one at a time.....what happens if this wire has come unstuck, broken etc....we have been jumping around a bit in the bottom servicing, rebuilding etc.

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the alarms operate on a ground condition, They "arm" with the key on,  At the res bottle 1 is hot to alarm, other is ground, water temp and oil pressure switches produce a ground with high temp or no oil pressure

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I have a boat that uses two stroke oil and it has a oil reservoir.  One time the magnet came off the float sensor and would continue to trip the "low oil" alarm.

You can use a multi meter and check the sensors.  

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1 hour ago, SOUTHERN CROSS said:

thanks everyone. problem solved.....loose wire from thermastat to alarm. found it although the temp gauge was ok.

That's because there are two temperature senders. One feeds your helm display gauge and the other talks to the ECM.  W

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thanks wingnut.  You are amazing with your knowledge. I read all of your posts.  Thanks keep on helping everyone please. 

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7 hours ago, SOUTHERN CROSS said:

thanks wingnut.  You are amazing with your knowledge. I read all of your posts. 

Yeah, he's ok.  We'll keep him around for a little while longer I guess.

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Thought i would add to this topic as our mate Wingnut may get messaged in. 

Same boat now. Its got twin drives and i have replaced shift linkages amongst other things. 

starboard engine and drive are fine. problem is no forward gear on Port side (counter rotating) when in the water. reverse is fine. Can engage forward and reverse on the trailer with muffs. 

Is the problem in the lower drive unit. if so what is the prognosis. 

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5 hours ago, SOUTHERN CROSS said:

Thought i would add to this topic as our mate Wingnut may get messaged in. 

Same boat now. Its got twin drives and i have replaced shift linkages amongst other things. 

starboard engine and drive are fine. problem is no forward gear on Port side (counter rotating) when in the water. reverse is fine. Can engage forward and reverse on the trailer with muffs. 

Is the problem in the lower drive unit. if so what is the prognosis. 

My guess would be the rear shift cable. Disconnect it from the engine mounted shift lever and see if you can make it engage by hand. I'm guessing you have twin Alpha drives which use a simple dog clutch buried in the lower gear case just ahead of the prop and they either work or they don't as they are a simple device. A failing shift cable suffers from lateral deflection which can shift once in a while but not consistently. It may also be an adjustment issue where the neutral point is biased too far toward reverse, and not providing enough forward detent but you will confirm that when you hand shift it as you will be shifting without the normal travel limit. Getting a clean neutral even with a new cable is a little tricky as the shift interrupter switch comes into play and all the mechanical components must work in concert so that the momentary engine shut off, gear engagement, and throttle response all happen at the appropriate point in response to input from the helm station. That involves 3 cables, two switches, and several levers.  W

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Thanks for the tip of where to start. Yes they are Alpha drives gen 2. the one with the trouble is the Port side, counter-rotation.  I did as you said , disconnected the rear shift cable (incidentally it is new) and pushed on it and into reverse...no problem. Then pulled, then pulled harder and it seemed like it almost got into gear. Could hear the gears meshing...incidentally motor  was just idling. Seemed to me that there was about 2-3 mm (thats about 1/10 th of an inch ) play in the cable even after I took all the slack out of the inner cable by adjusting the fixing screws on the cable end. 

Could the problem be the gearbox or maybe just slack in the outdrive levers. 

Thanks. I guess my next step is to slip the boat and remove the outdrive. I prefer not to. 

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1 hour ago, SOUTHERN CROSS said:

Thanks for the tip of where to start. Yes they are Alpha drives gen 2. the one with the trouble is the Port side, counter-rotation.  I did as you said , disconnected the rear shift cable (incidentally it is new) and pushed on it and into reverse...no problem. Then pulled, then pulled harder and it seemed like it almost got into gear. Could hear the gears meshing...incidentally motor  was just idling. Seemed to me that there was about 2-3 mm (thats about 1/10 th of an inch ) play in the cable even after I took all the slack out of the inner cable by adjusting the fixing screws on the cable end. 

Could the problem be the gearbox or maybe just slack in the outdrive levers. 

Thanks. I guess my next step is to slip the boat and remove the outdrive. I prefer not to. 

The linkage between the cable and upper gear case lever is pretty straight forward. If you get in the water, you can feel the shifter foot where it exits the upper gear case and enters the lower one. Tilting the drive up about 30% will make it easier to get your hand in there. With a helper you should be able to affirm that the movement to that point is proper. I am leaning away from there being an issue in the lower unit as those Alpha dog clutches are not really clutches at all, but are simply a splined ring with square teeth. When they do fail (rare) it is usually because the output shaft bearing set has failed and excessive thrust causes the teeth on the "clutch" not to engage. Check the shaft for both run-out and end play travel where it exits the nose cone. Easier to do with the prop off. When the clutch is nested fully in-gear, the prop will lock in one direction, and will ratchet in the other if you attempt to rotate it by hand. The ratchet "feel" will show the same resistance in both forward and reverse if the cable adjustment is proper. The last thing I'll throw out there is the prop hub. They place an elastomer element between the splined prop shaft, and propeller hub called the prop bushing. (Alpha's only) When they fail they can lock in now and then and the next time you attempt a shift, they spin within themselves. You are actually in gear but think it not to be so as you have zero thrust.   W

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thanks. love the bit about getting in the water.....ok its not cold at this time of year. But before I do I dont understand a couple of things that you said to do. 

The shifter foot - how do i know that the movement is proper. how far should it move. should it be firm or should there be some slack. 

Is the OUTPUT shaft the shaft that the prop attaches to? 

What is RUN OUT and END PLAY TRAVEL ?

I have been in the water before and the prop locks into gear when turned by hand but i need to check if the feel is the same for forward and reverse. Finally you mentioned the prop-hub. As i said before The drive is not engaging forward, just get that clunking sound so I guess we can discount the prop-hub. 

Thanks for the answers in anticipation. I guess if all this fails I will need to slip the boat and pull the outdrive off- all of it or just the lower unit. 

Thanks SC

 

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The foot is rectangular and will be pointing straight forward when the drive is in forward gear. When shifted into reverse, it will rotate about 75 degrees, and neutral will be found at the mid-point of that rotation. If you lock it in neutral with your fingers, have your helper move the helm shifter in small increments until you feel movement. Then have him move the shifter in the opposite direction until you again feel the foot reverse its direction. That handle movement represents the amount of play in the linkage from the helm to the foot. You said that the shifting action locked the prop in gear. You should not be able to turn the prop in one direction as stated, but you should be able to force it to move in the other while at the same time you should hear a ratcheting noise. It won't take much force and does no harm as this is normal. This should happen in both forward and reverse and the ratcheting action should require about equal force, as an indication that your cable adjustment is proper. If the resistance is heavy in one direction, and barely noticeable in the other then you are over-shifting into that "heavy" direction and under-shifting into the other. This is what I think may be happening in your case. Getting the shift linkage set right on an Alpha can be a challenge and requires that you follow all the prescribed steps in sequence as described in the manual, as A, impacts B, which influences C, and effects D, and so on.Neutral should be clean and you should hear no ratcheting at all. Run-out and end-play of the propeller shaft is measured by grabbing the prop with both hands and pushing it forward and back. Some play is normal, and the shaft (and prop) should move about .009" in total on a fresh out drive. That's your end-play. Moving the prop up and down is an indication of bearing play/wear and rotating the shaft with a dial indicator resting on a flat concentric area of the shaft is a check for run-out. (bent shaft).   A bearing failure is usually accompanied by a related seal leak where the shaft exits the housing so again I do not think this is your issue. Likely you need to affirm that the cable adjustment sequence has been followed per the manual with no steps skipped, and if so it may be time to pull the lower gear case. As the issue would be just ahead of the props, you could just pull the lower gear case and leave the upper attached to the boat, but while the cases are parted, be sure to inspect and/or replace the raw water pump impeller as it mounts to the top of the lower gear case. If you don't have the manual, send me a pm with a valid email address and I'll send you the procedure, just don't rush through the steps as this is your last shot at a fix before you get into the expensive out drive repair work. Good Luck     W

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