2007 Mercruiser 496 HO Mag ignition issue

[nasdaqsam]

Out boating tonight pulling kids on a tube. Shut it off and started it several times no issue. Then the last time the gauges all go backwards like reverse polarity to them it did this several times but then the switch went dead, it did no try to start when doing this. There is power to the switch but nothing on the dash. 50 amp circuit breaker has power to both sides. All battery connections are good. It does nothing when trying to jump across the power to striped wire.

​My thought is the selanoid is fried but no way to get to it short of removing all the exhaust and bunch of hoses so looking for everything to eliminate first.

Ideas?

 

[alldodge]

It does nothing when trying to jump across the power to striped wire.

Are you talking about the slave solenoid and your crossing the top two large terminals (Red/Pur to Yel/Red)?

 

[nasdaqsam]

Are you talking about the slave solenoid and your crossing the top two large terminals (Red/Pur to Yel/Red)?

No on the ignition switch. The Red to the purple or yel/Red makes no difference I am not getting anything on either. Were would the slave solenoid be? The battery cable goes across the back of the engine up underneath there is no way to see if like I said short of removing all the exhaust and plumbing on the back of the motor first. Its too tight to even try to get my cell phone down in there to try and take a picture of it. This thing is wall to wall engine.

I talked to a local mechanic here he said to check the big round plug on top of the motor also he said they sometimes will seperate just enough to act like this but that's a long shot.

 

[alldodge]

Here is the starting circuit
Note the Red from starter goes to 50 amp breaker, then changes to Red/Purple at the (c) slave solenoid along with going to the key switch.

When key is turned to start it goes to the Yel/Red, thru the neutral safety switch (g) then to the small terminal Yel/Red. The slave solenoid is energized and main power is switched to the starter solenoid.

The slave is on top the motor and will have a plastic cover over the two larger terminals on top. If the two large terminals are jumped across the start will turn over the motor. So what you want to find out is there 12V on the small terminal Yel/Red wire when the key is turned to start. If there is and the motor does not crank, then its the slave solenoid

Slave Solenoid

 

[nasdaqsam]

There is something like that on top of the motor but it has a red bottom coming out of the back side of it. I assumed that was the 50 amp circuit breaker. It does not have the two small side terminals. Is this the same thing or is this another part I need to locate? The one that is there has power on both sides of the larger terminals.

Edit: Actually looking at the diagram it looks like there is both but I didn't see the slave anywhere I will have to look again.

 

[alldodge]

Yes they are two different parts, and the red button is the breaker
Removing and reinstalling the main engine connector is a good thing to check as the other fella mentioned

 

[nasdaqsam]

Yes they are two different parts, and the red button is the breaker
Removing and reinstalling the main engine connector is a good thing to check as the other fella mentioned

Ok, I will give both a try tonight when I am back at the boat. Thanks

 

[Fun Times]

There is something like that on top of the motor but it has a red bottom coming out of the back side of it. I assumed that was the 50 amp circuit breaker. It does not have the two small side terminals. Is this the same thing or is this another part I need to locate? The one that is there has power on both sides of the larger terminals.

Edit: Actually looking at the diagram it looks like there is both but I didn't see the slave anywhere I will have to look again.

Having your engine serial number would help us some too in order to know if the engine Digital Throttle and Shift or Mechanical Shift, etc.

The 496 engines uses a relay system vs the Slave Solenoid but the concept is the same just a bit more challenging to figure out the wiring to test or jumper vs the Slave Solenoid as the wiring is more out in the open as to where the relay is not. http://www.mercruiserparts.com/bam/subassembly/31818/11746/30

Since it seems you may have 12v power going to the key switch red wire and 12v at the 50 amp breaker then it sort of sounds like a "possible" issue with the purple wake up power wire circuit/system. There are many fuses on the engine and possibly one or two found under the dash area too that could have failed, so be sure to thoroughly find and inspect them all. Also the relays may have become defective as well...Sometimes switching the relays and or tapping on them in case they are stuck might help tell a story if anything seemed to change in operation.

Are you using smart craft digital gauge system?

 

[nasdaqsam]

Having your engine serial number would help us some too in order to know if the engine Digital Throttle and Shift or Mechanical Shift, etc.

The 496 engines uses a relay system vs the Slave Solenoid but the concept is the same just a bit more challenging to figure out the wiring to test or jumper vs the Slave Solenoid as the wiring is more out in the open as to where the relay is not. http://www.mercruiserparts.com/bam/s...31818/11746/30

Since it seems you may have 12v power going to the key switch red wire and 12v at the 50 amp breaker then it sort of sounds like a "possible" issue with the purple wake up power wire circuit/system. There are many fuses on the engine and possibly one or two found under the dash area too that could have failed, so be sure to thoroughly find and inspect them all. Also the relays may have become defective as well...Sometimes switching the relays and or tapping on them in case they are stuck might help tell a story if anything seemed to change in operation.

Are you using smart craft digital gauge system?

I do not have the model on me but will get it tonight and post it here. From what I can see it has a mechanical shift.

With the Purple wire if I jump it nothing happens. I went through all the fuses I could find but like a lot of boats there is a mess of wiring under the dash so could easily have missed one or two. I will check that tonight as well.

I have a few things to look at tonight I really appreciate all the assistance.

What is the smart craft digital gauge system? This is Southbay Trifecta pontoon. Whatever came stock is what it has for gauges.

 

[alldodge]

I know your right (always are) FT but I'm still going to scratch my head on this one. The pic posted above came from manual 33, and the pic below also comes from the same manual. Both list the slave solenoid and the link you posted shows the relays for digital shift, main power and fuel pump. Have to be missing something but sure could use some help understanding where the relay is?

 

[Fun Times]

Thanks AD, I know it's confusing because I even almost forgot they went to a relay system vs the slave solenoid starting somewhere in 05 - 06 I believe it to be. But looking at the serial number breaks helped remind me (496 MAG (H.O. Model) - 0M687144 THRU 0W059999 = Slave Solenoid) the first two serial number ranges used the slave solenoid while the third set of serial numbers on up went to / show the relay system. 496 MAG (H.O. Model) - 0W060000 THRU 0W309999 +.

Slave shown, http://www.mercruiserparts.com/bam/subassembly/31823/6708/30
No slave shown, http://www.mercruiserparts.com/bam/subassembly/31825/11415/40 which show more relays (4) by the PCM,http://www.mercruiserparts.com/bam/subassembly/31825/11415/30

Those 2 manuals (33 & 36) were written somewhere around 2002ish so they only show the older stuff. in 2007, Merc stopped showing newer designed wiring harnesses, fuel flow direction, and water cooling flow directions within the service manuals like they used to do that we tend to refer to often here on the forums for better helping power. They created a paper back binder (folder) for each engine model made from 07 on up and send them out to their dealers to add to the binder. It's a special type of paper that you can easily mark on to help follow a wire then wipe it clean afterword's if you desire too. You can even remove any greasy finger prints too. I forget what kind of paper they call it.

 

[nasdaqsam]

Great thread and lots of good info. I will keep all this info for future use for sure. Turns out it was a blown fuse but the fuse block location is ridiculous. It is shoveed way up under the dash in a corner behind a massive stereo amp. The only way I lucked out and found it is because someone had put a lit fuse in it, there was just enough light to draw my attention. The fuse even tests as good but it is isn't. Changed it out, the ignition beeped and she started right up. Whoever designed the location didn't think it through. There is a ton of room under this dash no reason to put it were it is.

​Thanks for all the help it is greatly appreciated.

 

[Fun Times]

Good to hear you were able to find and repair your problem. Be sure to keep extra fuses onboard just in case it wasn't a fluke that popped.

That Southbay Trifecta pontoon must run pretty good with the 496 HO in it. Just watched a video of one running a said to be 600 HP Merc racing engine in it. https://www.youtube.com/watch?v=SCEF6zOFj2o

 

[nasdaqsam]

Good to hear you were able to find and repair your problem. Be sure to keep extra fuses onboard just in case it wasn't a fluke that popped.

That Southbay Trifecta pontoon must run pretty good with the 496 HO in it. Just watched a video of one running a said to be 600 HP Merc racing engine in it. https://www.youtube.com/watch?v=SCEF6zOFj2o

She runs pretty good. On a perfect day, just me running it, empty accept for basic safety equipment with around 10 gallons of gas, on a 1' to 2' chop into the wind that's how she runs best she will run right at 60 on my humminbird GPS. I have to get it to bounce then go up a little or turn slightly and she'll hit it. But all day long she will run in the low to mid 50's. but what I like best is how great it takes the waves so smoothly. I have had to bring a lot of the former owners "fixes" back to original but I have direct contact with the Hull designer he has been great at giving me info.