Intermittent engine alarm

[nigel]

Anyone had experience of anything like this before??

When at cruise speed my audible alarm intermittently cuts in (and is very annoying :smt013) - even though drive oil level is OK and oil pressure and temp are OK on the gauges. If I reduce the revs a bit on my port engine I percieve it to go away a bit... but its so intermittent I could be wrong.

It also seems to happen in rough seas more and when I'm on the verge of being trimmed out too far. It has also got worse over the last two seasons: from now-and-again on a long trip to within 10 to 15 mins of getting on the plane now.

My feeling is that it could be the oil pressure switch or cabling... but maybe there is actually a real fault in there somewhere.

Engines are 4.3Ls with Alphas.

 

[Dave S]

You didn't mention the boat model and year so we don't know if you are Smartcraft Equipped or not.

If you have Smartcraft, it should store a fault for any alarm that goes off. A Mercury tech will have to hook up his Scan tool to take a look at what is stored.

 

[TheAcademy5]

I had that happen, but with more regularity. Turned out to be a 5 dollar part, engine manifold sensor or something.

 

[boatrboy]

FWIW - I had an alarm go off after my first hour cruise to my dock. This did not happen during my sea trial, only after I brought her home. I checked the oil press, the water temp, and the outdrive oil level too. I had mine scanned and the fault said "knock sensor" problem. I contacted mercruiser and they said that would not cause the alarm to go off - THEY WERE WRONG!

I chased this problem like this for a month and finally had the dealer chase it for weeks. The dealer had to replace both knock sensors, just like the computer said..... :smt021

Good luck.

Mark

 

[STIHLBOLTS]

Sometimes the simplest of things can drive you nuts. :smt101

 

[nigel]

Knock sensors

Thanks everyone - knock sensors are certainly something I wouldn't have even considered.. Not sure how I'll check them though!

My boat is a '98 270 Sundancer with 4.3L carb engines. I don't think these have a stored fault computer... do they?

Cheers,

Nigel.

 

[Dave S]

There is one other thing you may want to check. I was told my a marine mechanic that it is not uncommon for the "neutral switch" to loosen up and become misaligned. If that happens and the props are still spinning, an alarm will sound.

Even though I have never had the misalignment problem myself, I have expereinced a momentary alarm several times when going into neutral abrubtly from a very high speed. It stopped when my props stopped spinning. The mechanic explained to me that essentially the same thing was happening as I described above.

So I suppose this may be another possibility you want to check out.

 

[Hotlanta]

I had the same problem after delivery of my 270SD.
I turned out to be the lower unit Lub level sensor. We disconnected it and the arlarm went away. Then they replaced it during first service

 

[boatrboy]

Re: Knock sensors

... knock sensors are certainly something I wouldn't have even considered.. Not sure how I'll check them though!
My boat is a '98 270 Sundancer with 4.3L carb engines. I don't think these have a stored fault computer... do they?
Cheers,
Nigel.

They are stored codes. If I remember correctly they only output 1 code, you have to figure out which side, at least on my boat. BTW I don't even know if the v-6's have knock sensors?

 

[nigel]

Solved!! - And nothing I'd have thought of!!

Edit: I thought I'd fixed this - but, nope, the problem is still there!

 

[nigel]

This overheat alarm is driving me mad!

Since starting the original thread I've had the impeller changed, swapped out the transom-to-oil-cooler hose (getting rotten), replaced the oil cooler itself (which was leaking slightly), the manifolds, risers and elbows (which were 12 years old), and this weekend, the circulation pump (the bearings gave up). Also swapped over the ingnition ECUs to make sure one of them wasn't playing up and causing the alarm. New thermostat and cleaned out the thermostat housing (which was corroded but OK - I think).

On the guage the engine runs slightly above 170 deg but nothing too serious. The alarm only sends after about 20 mins or so and when plaining. As soon as I back off the power on the engine the alarm cuts off instantly. Will also cut off sometimes if I adjust the trim.

I do wonder if I have an earthing issue or something else electrical but can't work out where this would be to cause the alarm to sound: if I unplug the temp alarm sender (which is resistive on this year of carb engine, not a switch) then the alarm never sounds..

If anyone has any ideas I'd be very keen to hear from you!

Cheers for now,


Nigel.

 

[Deanord]

Nigel,
having exactly the same issues with ours - did you ever resolve this issue?
thanks
Jon