Which alarm is it? What's wrong with these spark plugs.

lkgboater71 · Jul 31, 2013

Hi all -

I have a 2006 Merc 5.0 TKS with an intermittent alarm. From what I understand there are 3 reasons the alarm would go off.

1) Oil Pressure. Always between 40-80.
2) Temp. Varies between 160 - 178 depending on load. I just replaced the thermostat to be sure that wasn't the issue and impeller is new this season.
3) Gear lube level. It's about an inch below full.

Any way to determine which alarm is actually sounding?

Attached is a picture of the spark plugs I just pulled out (A/C MR43LTS) with about 40 hours on them. They are from cylinders (starting from right is #1 cylinder and the left is #7) 7,5,3,1. The plug in cylinder 5 looks like it hasn't done a days work in all 40 hours. It looks more dramatic than in the pictures. Plugs in cylinders 2,4,6,8 look like the ones in cylinders 1,3,7. I just replaced the cap/rotor/wires/plugs as well.

Could there be something wrong with cylinder #5? Acceleration seems sluggish.
Thanks!

achris · Jul 31, 2013

Re: Which alarm is it? What's wrong with these spark plugs.

The alarm switches (the 3 you mentioned) work by grounding a wire. If you disconnect the tan/blue wire from each of the switches, that will find you culprit.

As for the clean plug. 2 things I'd check. one is that it could be clean because it's getting washed. Check for elbow/manifold leaks. The other possibility is it's not firing. How is the engine running? Next time you have the engine running, just pull #5 plug lead off. You should hear a slight drop in engine speed. If you don't hear any difference, that cylinder is not contributing... Time to find out why.

Chris......

alldodge · Jul 31, 2013

Re: Which alarm is it? What's wrong with these spark plugs.

Not knowing what engine you have, is it a solid alarm beep or a 2 beep every few seconds

lkgboater71 · Aug 1, 2013

Re: Which alarm is it? What's wrong with these spark plugs.

achris said:
The alarm switches (the 3 you mentioned) work by grounding a wire. If you disconnect the tan/blue wire from each of the switches, that will find you culprit.

As for the clean plug. 2 things I'd check. one is that it could be clean because it's getting washed. Check for elbow/manifold leaks. The other possibility is it's not firing. How is the engine running? Next time you have the engine running, just pull #5 plug lead off. You should hear a slight drop in engine speed. If you don't hear any difference, that cylinder is not contributing... Time to find out why.

Chris......

It's definitely the temp alarm. I unplugged the temp switch and the alarm doesn't sound anymore. Is there any way to tell if it's more likely the switch or if something happened to the impeller?

Hint: When you bring your boat to the lake, don't leave the service manuals at home....

Appreciate the help.

--
Shawn.

alldodge · Aug 1, 2013

Re: Which alarm is it? What's wrong with these spark plugs.

lkgboater71 said:
It's definitely the temp alarm. I unplugged the temp switch and the alarm doesn't sound anymore. Is there any way to tell if it's more likely the switch or if something happened to the impeller?

Hint: When you bring your boat to the lake, don't leave the service manuals at home....

Appreciate the help.

--
Shawn.

Put an ohm meter on the end if the terminal and the other end to the side of it or engine block. You should show an open circuit, if it shows a short the sender is bad with a cold and warm engine. To test the sender, place it in a pan of water and use a thermometer. When the water reaches 200 it should close the switch and show a short. If your engine is getting overheated you should be able to smell it with burning paint and oil.

lkgboater71 · Aug 1, 2013

Re: Which alarm is it? What's wrong with these spark plugs.

AllDodge said:
Put an ohm meter on the end if the terminal and the other end to the side of it or engine block. You should show an open circuit, if it shows a short the sender is bad with a cold and warm engine. To test the sender, place it in a pan of water and use a thermometer. When the water reaches 200 it should close the switch and show a short. If your engine is getting overheated you should be able to smell it with burning paint and oil.

I'll give that a shot. I realize that the console gauges aren't always accurate, but it's showing nowhere near 200. So these switches are supposed to trip at 200?

Thanks!

--
Shawn.

Sergi · Aug 1, 2013

Re: Which alarm is it? What's wrong with these spark plugs.

That "clean" plug may be indicating lean condition on that cylinder or too hot (one by hand to other)
I don't know about the engine, but I could be FI?

alldodge · Aug 1, 2013

Re: Which alarm is it? What's wrong with these spark plugs.

lkgboater71 said:
I'll give that a shot. I realize that the console gauges aren't always accurate, but it's showing nowhere near 200. So these switches are supposed to trip at 200?

Thanks!

--
Shawn.

Probably more like 210 to 220, but figure if it hangs in there up to 200 it should be close enough. At 212 and sealevel water boils

achris · Aug 1, 2013

Re: Which alarm is it? What's wrong with these spark plugs.

lkgboater71 said:
Hi all -

I have a 2006 Merc 5.0 TKS with an intermittent alarm. From what I understand there are 3 reasons the alarm would go off.

AllDodge said:
Not knowing what engine you have, is it a solid alarm beep or a 2 beep every few seconds

Sergi said:
That "clean" plug may be indicating lean condition on that cylinder or too hot (one by hand to other)
I don't know about the engine, but I could be FI?

Am I the only one who saw that ^?

AllDodge said:
Probably more like 210 to 220, but figure if it hangs in there up to 200 it should be close enough. At 212 and sealevel water boils

Nice touch

Ok... All said about the temp switch is correct. With the engine cold/cool or at normal temperature the switch should be open circuit.

Chris....

alldodge · Aug 1, 2013

Re: Which alarm is it? What's wrong with these spark plugs.

achris said:
Am I the only one who saw that ^?

Nice touch

Ok... All said about the temp switch is correct. With the engine cold/cool or at normal temperature the switch should be open circuit.

Chris....

I for one am sure gald someone of your type is around is here just to help all of us. I get all warm a fussy just knowing you have are back andthat you try so hard to make everyone feel welcome to try and help.

NHGuy · Aug 1, 2013

Re: Which alarm is it? What's wrong with these spark plugs.

Chris, I saw the TKS. I don't mind saying that you don't make me feel fuzzy! Or Fizzy, Or Fussy, or something... Although I trust your boat repair logic absolutely!

Sergi · Aug 2, 2013

Re: Which alarm is it? What's wrong with these spark plugs.

achris said:
Am I the only one who saw that ^?

@Chris: Sorry still new on that marine thing and can't recognize when someone refers to TKS or anything like. Stupid me, as the year and displacement OP talked can only be EFI. Didn't pay attention on the displacement and feared it could be an outboard. Sorry.

What I think about. I think is something wrong with the 5th injector. I would do some tests to it, like test impedance to specs at it's connector. Test the wiring harness side for shorts. Unplugging and seeing if its spraying fuel while running.
Or even exchanging injector and plug to some other cylinder, run and see if the plug shows more "used".

1- I'm convinced that plug is running, as it shows burned deposits on the main.
2- It's unlikely for an injector to stick closed. It may be some failure on your wiring harness causing that injector not to spray and the temp signal issue.

So alarm could indicate injector pulse miss.
Hope I'm any help. :concern:

lkgboater71 · Aug 2, 2013

Re: Which alarm is it? What's wrong with these spark plugs.

Sergi said:
@Chris: Sorry still new on that marine thing and can't recognize when someone refers to TKS or anything like. Stupid me, as the year and displacement OP talked can only be EFI. Didn't pay attention on the displacement and feared it could be an outboard. Sorry.

What I think about. I think is something wrong with the 5th injector. I would do some tests to it, like test impedance to specs at it's connector. Test the wiring harness side for shorts. Unplugging and seeing if its spraying fuel while running.
Or even exchanging injector and plug to some other cylinder, run and see if the plug shows more "used".

1- I'm convinced that plug is running, as it shows burned deposits on the main.
2- It's unlikely for an injector to stick closed. It may be some failure on your wiring harness causing that injector not to spray and the temp signal issue.

So alarm could indicate injector pulse miss.
Hope I'm any help. :concern:

Hi All -

Going to replace the temp switch in a few minutes. The engine has a Turn Key Start carb and is not EFI. (sn 0W675909). I pulled #5 plug wire and the RPMs drop so the cylinder seems to be working.

Thanks.

--
Shawn.

Sergi · Aug 2, 2013

Re: Which alarm is it? What's wrong with these spark plugs.

lkgboater71 said:
The engine has a Turn Key Start carb and is not EFI.

:facepalm:

lkgboater71 · Aug 2, 2013

Re: Which alarm is it? What's wrong with these spark plugs.

One down! I ran WOT for about 2 minutes and the temp climbed to 180 on the gauge briefly and no alarm! But the boat only hit 4200 RPM trimmed out with 1/3 tank of fuel WOT. Normally 4800. Related to cylinder #5 perhaps? Time to go through the WOT FAQ and check the elbow.
Thanks!

--
Shawn.

lkgboater71 · Aug 2, 2013

Re: Which alarm is it? What's wrong with these spark plugs.

Well the alarm went off again. I guess the only thing left is the impeller. I'll pull that this weekend. *sigh*

lkgboater71 · Aug 3, 2013

Re: Which alarm is it? What's wrong with these spark plugs.

lkgboater71 said:
Well the alarm went off again. I guess the only thing left is the impeller. I'll pull that this weekend. *sigh*

I replaced the impeller, but the old one looked brand new. I also replaced the exhaust flappers. I hooked it up to the muffs and I seem to be getting a good flow of water. I did notice water spraying out of where the shift linkage and the speedo connector is. Is this normal?

achris · Aug 3, 2013

Re: Which alarm is it? What's wrong with these spark plugs.

Can't quite make it out in the photo... Generally you shouldn't be getting water coming out in that area. It could indicate a pump leak of some sort...

Chris....

Which alarm is it? What's wrong with these spark plugs.

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