MerCruiser 5.0 (Carb Engine) will not turn, what is this part?

[Robertse]

MerCruiser 5.0 will not start/turn due at minor quick fire. While the exhaust manifolds off the engine (for service), I started the engine and port (left) and rear side part of the engine caught on fire for a few seconds. I put the fire out quickly with a fire extinguisher. Now the engine will not turn at all (nothing at all), so I believe there is an electrical problem, the part in the photo was had prior rush and got damage further in the fire, but I don’t know what the part is called, to order a replacement. The starter motor works fine, as I connected direct power to it and it works as normal. The engine had good compression prior to the mini fire. Any help will be appreciated, what is the part called, and what else should I check. Thankyou in advance.​

 

[Chris1956]

Gee, will it turn over with the spark plugs removed, using a wrench on the main pulley?

Fire extinguisher dry chemical is both course and caustic to metal. If the carb sucked some of it in, or some went into the exhaust port, it could be gumming up the works.

 

[Robertse]

Hi Chris, Thanks for the reply. No it will not turn over; there is no ignition, nothing. I think it is an electrical problem. There is power going to the fuel pump, , trim and windlass anchor, there is power to teh starter, but not the ignition, I don’t know where to look in relation to the issue. I will try to turn the engine manually using wrench and will clean extinguisher dry chemical. Any other clues/feedback will be much appreciated.

 

[alldodge]

Don't use a wrench on the crank bolt, it can be snapped off doing it. Turn motor over using the pulley and or belts

Assuming this is a stern drive I/O, the port side rear of a 5.0 is where the oil pressure sensor and oil filter remote is attached. It motor is EFI then there can also be a fuel pump

There is a square block attached to the starter post which has other wires connected, this is a 90 amp fuse. The fuse is inside the block

 

[tank1949]

Hi Chris, Thanks for the reply. No it will not turn over; there is no ignition, nothing. I think it is an electrical problem. There is power going to the fuel pump, , trim and windlass anchor, there is power to teh starter, but not the ignition, I don’t know where to look in relation to the issue. I will try to turn the engine manually using wrench and will clean extinguisher dry chemical. Any other clues/feedback will be much appreciated.

Before proceeding, what caused the fire? Usually, it is battery or fuel related. Check battery charge and cables going to starter. Of OK, manually jump starter using screwdriver or something else to cross contacts at starter. If motor spins, look for any burnt electrical wires related to motor. Use mirror if necessary to examine under motor.

 

[Robertse]

Don't use a wrench on the crank bolt, it can be snapped off doing it. Turn motor over using the pulley and or belts

Assuming this is a stern drive I/O, the port side rear of a 5.0 is where the oil pressure sensor and oil filter remote is attached. It motor is EFI then there can also be a fuel pump

There is a square block attached to the starter post which has other wires connected, this is a 90 amp fuse. The fuse is inside the block

Hi, thanks for the reply. is the Fuse in a small block next to the starter? I have tried to upload a photo, but it fails.

 

[alldodge]

Hi, thanks for the reply. is the Fuse in a small block next to the starter? I have tried to upload a photo, but it fails.

Not next to but on starter post. Search merc 90 a.p fuse a Pic should show up

Yes pics not working

 

[Robertse]

Hi All Dodge, I have replaced the Merc90 Fuse and the same problem is occurring. I also replace a small 20amp fuse behind the distributor. I connected power directory to the starter motor and it worked, but it will not work via the ignition key. I am not sure what the problem is. Any help will be appreciated

 

[Bondo]

Hi All Dodge, I have replaced the Merc90 Fuse and the same problem is occurring. I also replace a small 20amp fuse behind the distributor. I connected power directory to the starter motor and it worked, but it will not work via the ignition key. I am not sure what the problem is. Any help will be appreciated

Ayuh,..... Welcome Aboard,..... At the keyswitch, with a test light, is there power at the battery terminal,..?? Usually a red wire,...
With the key "On", is there power at the ignition terminal,..?? Usually a purple wire,....
With the key to "Start", is there power at the start terminal,..?? Usually a yellow/ red wire,....
If no on the yellow/ red wire, is the control in neutral,..?? if not, shake the handle, 'n try again, as the power goes through the neutral safety switch there,....
If yes, is there power at the yellow/ red wire at the slave solenoid,..??
If yes, is there power at the yellow/ red wire on the starter,..??
If yes, the starter will engage,.......

 

[alldodge]

Need a voltmeter to find out where power is being lost.

I really need the motor serial number

Look for the slave relay

The top post will have larger red/purple and yellow/red wires. The red/pur comes from the 50 amp breaker and the yel/red goes to the starter solenoid

Cross the top post and see if starter engages.
If it does not engage then there is a bad 50 amp breaker or needs reset, or a bad red/pur wire coming from the starter

If it does engage starter then need to test the relay.
The smaller bottom to post will have a smaller Yel/red wire and a black wire. Use a jumper wire and jump from the top Red/pur down to the smaller yel/red. This should energize the relay and starter will engage

If it does not engage then relay needs replaced

If it does engage then with a voltmeter measure voltage on the Red/pur wire and there should be 12V

Next check for 12V on the yel/red wire when key is turned to start. You should get 12V

If 12V is not there check the neutral safety switch on the throttle. Turn key to start and hold key in position, now move the throttle a slight bit FWD/REV

Looks like Bondo is faster

 

[nola mike]

Need a voltmeter to find out where power is being lost.

I really need the motor serial number

Look for the slave relay

The top post will have larger red/purple and yellow/red wires. The red/pur comes from the 50 amp breaker and the yel/red goes to the starter solenoid

Cross the top post and see if starter engages.
If it does not engage then there is a bad 50 amp breaker or needs reset, or a bad red/pur wire coming from the starter

If it does engage starter then need to test the relay.
The smaller bottom to post will have a smaller Yel/red wire and a black wire. Use a jumper wire and jump from the top Red/pur down to the smaller yel/red. This should energize the relay and starter will engage

If it does not engage then relay needs replaced

If it does engage then with a voltmeter measure voltage on the Red/pur wire and there should be 12V

Next check for 12V on the yel/red wire when key is turned to start. You should get 12V

If 12V is there check the neutral safety switch on the throttle. Turn key to start and hold key in position, now move the throttle a slight bit FWD/REV

Looks like Bondo is faster

How did you post a pic? still not working for me...

 

[alldodge]

How did you post a pic? still not working for me...

I found a pic in another thread, copied the link, then posted it using "insert image" link
So a previous posted pic

 

[Robertse]

Don't use a wrench on the crank bolt, it can be snapped off doing it. Turn motor over using the pulley and or belts

Assuming this is a stern drive I/O, the port side rear of a 5.0 is where the oil pressure sensor and oil filter remote is attached. It motor is EFI then there can also be a fuel pump

There is a square block attached to the starter post which has other wires connected, this is a 90 amp fuse. The fuse is inside the block

Sorry for the Questioni, how do you turn the motor over using he pulley and or betls?

 

[Robertse]

Thanks again for the reply. You said "If no on the yellow/ red wire, is the control in neutral,..?? if not, shake the handle, 'n try again, as the power goes through the neutral safety switch there,.... """ Which handle do I shake, and sorry where is the neutral safety switch. When I turn the key, the dashboard light come on, the fuel pump starts, but there is not power comming to the yellow/red cable. I notice the yellow red cable goes to a relay, I repleaced the relay and still not luck. If I jumber the starter motor, the engine turns over. Thanks for your help in advance.

 

[alldodge]

Sorry for the Questioni, how do you turn the motor over using he pulley and or betls?

Motor can be moved by grabbing the belt and a pulley, then rotate clockwise. Can be done easier by removing the plugs.

Thanks again for the reply. You said "If no on the yellow/ red wire, is the control in neutral,..?? if not, shake the handle, 'n try again, as the power goes through the neutral safety switch there,.... """ Which handle do I shake, and sorry where is the neutral safety switch. When I turn the key, the dashboard light come on, the fuel pump starts, but there is not power comming to the yellow/red cable. I notice the yellow red cable goes to a relay, I repleaced the relay and still not luck. If I jumber the starter motor, the engine turns over. Thanks for your help in advance.

The neutral safety switch is inside the throttle/shifter handle.

Yel/Red comes from the key, to the neutral switch in the handle, then to the relay

 

[Robertse]

Motor can be moved by grabbing the belt and a pulley, then rotate clockwise. Can be done easier by removing the plugs.


The neutral safety switch is inside the throttle/shifter handle.

Yel/Red comes from the key, to the neutral switch in the handle, then to the relay

 

[Robertse]

Hi, I am still having this issue. I unlugged the relay which has the yellow/red and power cable connec to the connector which plugs into the replay. I connected the cable from the relay which works.

 

[Bondo]

Hi, I am still having this issue. I unlugged the relay which has the yellow/red and power cable connec to the connector which plugs into the replay. I connected the cable from the relay which works.

Ayuh,..... At the keyswitch, with a test light, is there power at the battery terminal,..?? Usually a red wire,...
With the key "On", is there power at the ignition terminal,..?? Usually a purple wire,....
With the key to "Start", is there power at the start terminal,..?? Usually a yellow/ red wire,....
If no on the yellow/ red wire, is the control in neutral,..?? if not, shake the handle, 'n try again, as the power goes through the neutral safety switch there,....
If yes, is there power at the yellow/ red wire at the slave solenoid,..??
If yes, is there power at the yellow/ red wire on the starter,..??
If yes, the starter will engage,.......