Oil Warning Siren

tablerockboater · Apr 24, 2005

Hi: My first time here. We have a '98 Merc 150 offshore carbureted. Last fall the oil warning siren went off. We know what that means so we trolled back in. We loosened the cap on the engine mounted oil reservoir and cranked the engine until it overflowed. It really wasn't low. That seemed to solve the problem. A month ago we got routine tune-up service at our dealer. Last week I ran across the lake and half way back the warning siren started again. I trolled back in again and top off the engine mounted oil reservoir again. It really wasn't low this time either. This time, however, the warning siren is still going off. I know the plunger in the cap-mounted sending unit can get saturated and not float any more, sending a false signal. What steps do I need to do to diagnose the problem: --cap mounted sending unit --warning module --oil pump. TIA.

wilde1j · Apr 24, 2005

Re: Oil Warning Siren

Try the shop manual. It gives very detailed info on trouble sghooting the oiling system.

tablerockboater · Apr 24, 2005

Re: Oil Warning Siren

Thanks, but I don't have one. How about a hint. Say if I disconnect the wires to the sending unit in the engine mounted oil reservoir and the siren still goes off, would that mean anything? PS--I like busy forums. Some take weeks to get a reply.

gss036 · Apr 24, 2005

Re: Oil Warning Siren

Pull the oil pump and see if you have a bunch of ground up plastic from the oil pump gear. If you do, you have a major decison to make on the fix. Might try loosening the cap for the on board oil tank and seek if oil is making it there. If it is you will get a little bit of over flow, ust retighten the cap, but not too tight, they have a tendancy to crack at the very top.

tablerockboater · Apr 25, 2005

Re: Oil Warning Siren

Originally posted by gss036: Pull the oil pump and see if you have a bunch of ground up plastic from the oil pump gear. If you do, you have a major decison to make on the fix. - - - - - - Major decision like replace the oil pump or premix from now on? - - - - - - Might try loosening the cap for the on board oil tank and seek if oil is making it there. If it is you will get a little bit of over flow, - - - - - - We did that, twice, and it is getting that far, and overflowing, which I mentioned in my opening post. That's good isn't it? Doesn't that eliminate some possibilities? - - - - - - ust retighten the cap, but not too tight, they have a tendancy to crack at the very top.

Yup, my nephew did that on my BIL's bass boat. If "tight" is good, "real tight" is better.

We have considered buying a new cap, with the float sensor and all, as a relatively cheap method of diagnosis. We would not want to, but if we have to premix, if we knew it was the pump not working, we could. Thanks. I'll be back tomorrow. Not the way I wanted this to appear, but dinner's ready.

admar · Apr 25, 2005

Re: Oil Warning Siren

how low is not too low in the engine oil tank? if system is working correctly this tanks level never drops. if it is dropping during use there is a problem with oil transfering to it from the boat mounted tank. hook up engine to 6gal tank with 50-1 premix. start engine on hose and let it idle for 10 mins., shut it off, loosen fill cap on boat tank , air should escape for a few seconds. if it does not tank is not receiving air pressure from engine, check orings in both caps on boat tank , check double hose for good clamps at both the boat end and the engine. if air does escape from tank, oil flow may be restricted; check for kinks, twists , rigging tie straps crushing hose, clogged oil pick up in boat mounted tank. if pick up is clogged replace don't clean.

tablerockboater · Apr 29, 2005

Re: Oil Warning Siren

Thanks. Very detailed checklist of things to look for. I'm here, asking, because I do not know what too low would be. When I check the engine mounted oil tank it is, to the untrained eye, at the top, near the top, whatever. When I loosen it and run the engine it takes no time at all to start overflowing. And there is a very strong flow. Then, when I tighten it and start the engine again the warning siren goes off immediately, before there would be any time for the oil level to drop, if it is dropping. I hate to just be guessing, but just trying to be logical, it is like the float is not floating any more, so the sensor is giving a false low reading. The cap(s) on the boat-mounted oil tank seem to be snug, and very tight. The rest of the stuff I just need to spend some time going through. If age may be a factor, it is a '98. For the first five years or so it did not get many hours at all. It has gotten more use the last couple of years.

tablerockboater · Apr 30, 2005

Re: Oil Warning Siren

Wow! What a great forum!!! I just dropped the boat in the water and cranked the engine and there's no oil warning siren whatsoever. I ran it across the lake, to blow some of the pollen off, and still no warning siren. I haven't touched a thing. You guys are great.

Let me start this thread over: What could cause an oil warning siren to go off occasionally, mysteriously, and then stop going off for no reason at all?

tablerockboater · May 11, 2005

Re: Oil Warning Siren

As you can see, it has been 11 days since the oil warning siren suddenly stopped going off. We've had the boat out several times. Last Saturday we had company and had it out a long time. I would guess we have run it 3 to 5 hours without the warning siren going off. Yesterday we had company again, dropped the boat in the water, cranked the engine, and the warning sirne was going off again, immediately. Judging from the normal amount of smoke coming from the engine (2-stroke) I assume it is still getting oil. We salvaged last night by trolling to the back of the cove and just sat there and ate fried chicken and drank sodas. I caught two really nice bass. So, what do you think now?

barroomhero · May 11, 2005

Re: Oil Warning Siren

How much smoke is comming out? Is it normal or really bad? When you unscrew the cap on the oil tank does it release air? Check to see if the check valve is working properly. Also make sure you keep a spare gallon of oil onboard.

tablerockboater · May 11, 2005

Re: Oil Warning Siren

I got a chance to look at it today. I did not run the engine first and I did not notice a release of air when I loosened the cap on the engine mounted oil reservoir. I didn't notice any cracks or anything abnormal about that cap. That reservoir was full. I ran the engine anyway, to where the reservoir overflowed. It did not take long, maybe three seconds. The oil warning siren was going off when the engine was running. I disconnected one of the wires going to the sensor in the cap of the engine mounted oil reservoir. When I ran the engine the siren still went off. Would that not suggest that it is not that sensor that is making the warning siren go off? The engine is it's normal amount of smoky. To me it is a little smokier than it should be, but it has been since our annual service three years ago. Before that we did not use it enough or pay attention enough to say whether it was smoky or not. The onboard oil tank is full and I clean the seal on the cap and around where it makes contact, then tightened it back down. The warning siren still went off. I have told our dealer about my concern for it's smokiness and they say it is normal. For now it is a big trolling boat, but we have a nice cove, so all is not lost.

gss036 · May 11, 2005

Re: Oil Warning Siren

You should probably run on premixed fuel until you figure out what the trouble is. Better safe than sorry. There may be a sensor for the oil pump that is causing the problem, since I am not a mechanic, I can't be much help, hopefully someone with some knowledge will jump in here and offer some good advice. Here is a link for engine manual, maybe it will help. http://www.biggerhammer.net/mercury/factory_manuals/ Just an after thought, follow the wires from the onboard oil tank around the right side of the engine and take off the ground wire and unplug the other wire and see what effect that has. Might be worth the investment for a new cap, they are about 50 bucks?

tablerockboater · May 12, 2005

Re: Oil Warning Siren

You are thinking like me, which could be dangerous! Yesterday I did disconnect the wire to the cap-mounted sensor, but not the ground. Just the wire that runs around the right side of the engine, as you are looking at it from the front. I have already thought about replacing the cap, since that is so inexpensive, but it looks fine, the engine mounted reservoir is staying full, and disconneting that wire did not stop the siren. I was just ready to replace it two weeks ago when it stopped going off. I have already asked my dealer about adding some oil to the gas tank and disconnecting the warning siren. He said too much oil will not hurt--in case the oil pump is still working. If I knew for sure the oil pump is not working I could make a decision--replace it or premix. Here's the thing I would like to know from someone who knows. Something is telling the warning siren to sound. I know about the cap-mounted float-type sensor. What else is there that activates the warning siren?

gss036 · May 12, 2005

Re: Oil Warning Siren

I am assuming your horn is going beep-beep-beep, not beeeeeeeeeeeeeeeeeeeeeeep. There is a motion sensor behind the oil pump on the motor. Check out this link and read for yourself, it gives good test procedures. It also tell you how to check the cap sensor. It also gives other tests and things to check. http://www.biggerhammer.net/mercury/factory_manuals/Service Manual PDFs/TwoStroke/824052r3/3e.pdf

tablerockboater · May 13, 2005

Re: Oil Warning Siren

Thanks for the link. I'll go look. Yesterday we wanted to run across the lake and look at a dock so I went ahead and pre-mixed the gas in our tank, and disconnected the warning siren. It's amazing how much racket that little plastic thing can make.

CU2NITE · May 13, 2005

Re: Oil Warning Siren

If you can't figure it out you can always pre-mix! It's nice to have no worries about that oil system failing frying your motor. Just disconnect oil system, put a dummy shaft in to hold the internal gear in place, pre-mix and go boating. It will smoke a bit more at idle, but it will run the same. Just a thought. Good luck. CU --------------------- RUNNING THE MOTOR WHILE LISTENING TO THE HORN WILL MAKE YOU MORN!!

tablerockboater · May 14, 2005

Re: Oil Warning Siren

First, I don't believe it could smoke more at idle.

I would not mind premixing if I knew the pump was not working. That is what I am trying to figure out. The link to the Mercury manual is excellent.

jeffpalmer@earthlink.net · May 16, 2005

Re: Oil Warning Siren

Originally posted by CU2NITE: If you can't figure it out you can always pre-mix! It's nice to have no worries about that oil system failing frying your motor. Just disconnect oil system, put a dummy shaft in to hold the internal gear in place, pre-mix and go boating. It will smoke a bit more at idle, but it will run the same. Just a thought. Good luck. CU --------------------- RUNNING THE MOTOR WHILE LISTENING TO THE HORN WILL MAKE YOU MORN!!

jeffpalmer@earthlink.net · May 16, 2005

Re: Oil Warning Siren

I have the same problem. I have a 1993 150 hp carburated V6. I first disconnected the hose from the oil pump (running on a remote tank with 50:1 mixture) and no oil came out of the oil line from the pump. Then I pulled the pump and turned the engine over. The shaft that drives the oil pump did not turn. Someone had mentioned looking for plastic shavings, etc. but I did not see any. After looking at the link with the service manual, I am assuming that my drive gear inside is worn out. I'm assuming that to replace this would be a major teardown, does anyone know if I can get to it through the intake or exhaust manifold or do I need to pull the whole powerhead and split the crankcase? Also, CU2NITE mentioned a dummy shaft, why is that necessary? Can I just leave the regular shaft in place? Is the drive gear on the crankshaft a fiber gear or plastic, metal, what? Thanks,

jeffpalmer@earthlink.net · May 16, 2005

Re: Oil Warning Siren

Here's the thing I would like to know from someone who knows. Something is telling the warning siren to sound. I know about the cap-mounted float-type sensor. What else is there that activates the warning siren?

The manual that came with my '93 150 hp has the following: The warning horn sounds continuously: beeeeeeee.. The problem is engine overheat. Check your water flowing out of the water pump indicator hole. (I think you said sometimes it started going off immediately, so you might rule this out) The warning horn sounds intermittent short beeps: beep beep beep beep (very annoying, I know) Possible problems: Low oil level (I think we've beaten this one to death). On electronic Fuel Injection models (I believe you said your's was carburated, so this won't apply), The water separating fuel filter is full of water. To check, turn ignition on and check to see if the red warning light is on. The light is located low on the front of the engine if the picture in the manual is correct. Finally: If the oil reservoir tank is full of oil, then the problem may be in the oil injection pump.

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