Mercruiser Neutral Safety Switch?

Brosport05

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Jul 15, 2025
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Re: Mercruiser Neutral Safety Switch

Something else worth checking is the fuse holder in the power lead to the keyswitch... dirty contacts and no power to nothing!!! Seen it happen... Enough current will get through to run the gauges, but not enough for the starter solenoid...

Chris........
Hey guys I am having the issue of my boat not starting. I have literally checked everything and cleaned everything and I cannot figure out the problem. I’m down to the neutral safety switch. I see where someone said you can disconnect the wires and twist the wires together to see if it is the switch. Ur saying to cut both wires and twist them together correct?
 

alldodge

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Welcome
Is the motor cranking and not starting or not cranking when the key is turned?
 

Brosport05

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Hey guys, sorry I was away for a min. But to answer ALLDODGE. The engine will not crank turn over or nothing. I turn the key and nothing happens. The dash lights do not come on, fuel pump doesn’t prime nothing happens. I have checked everything that I can think of. Cleaned all terminal ends checked fuses. I don’t know what else to do or check. I’m down to it being the control module. Any suggestions
 

Brosport05

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Pic of control box. Does anyone know where I can source one of these?
 

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bajaman123

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May 6, 2009
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107
What has taken place since it DID crank and start okay? Has there been ANY work done to it? If so, THAT is the first place to start looking. What year and model of engine? What type of control handle for drive/throttle? Have you check power to the ignition switch?
 

alldodge

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Hey guys, sorry I was away for a min. But to answer ALLDODGE. The engine will not crank turn over or nothing. I turn the key and nothing happens. The dash lights do not come on, fuel pump doesn’t prime nothing happens.
Thanks for clarifying
I'll now assume you do not have 12V on the red/purple wire on key switch, correct?

If this is the case, measure voltage on both sides of the 50 amp breaker, should be on both sides

If 12V is not on both sides measure voltage to the square fuse on the starter post

90 amp fuse.jpg
If no voltage on small post the fuse is blown inside
 

Brosport05

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Jul 15, 2025
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Baja man- no work has been done on the engine. I was on the water and all of a sudden the motor shut down. I heard a sound like a fuse blew and then the engine shut down. Try to turn key and nothing happens. No power to ignition switch. No power to the 50 amp fuse on the top of engine.
 

Brosport05

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Jul 15, 2025
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ALLDODGE- no power to the ignition switch at all. I looked at the fuse on the inside of the starter post. Does not look blown. I’ll take apart and send picture of the fuse.
 

Brosport05

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Ok so I checked the continuity on the fuse. Its good. When I went to put it back on and connected the battery, I heard a noise, sounded like fuel pump. Then I had a feeling it would crank and I’d have dash lights. Well in fact I did. I put ears on and cranked it up. It cranked rite up and ran for about 5 seconds and shut back down. Yet again have no dash lights and doesn’t do anything when turn the key. I looked and noticed it popped the fuse the 15 amp one on back of motor that is in the main harness. I’m not sure what the problem is!!!
 

alldodge

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Removed the fuse and cable, reinstalled and it started to work but has issues

Remove all the cables from Bat to starter including the Ground cable to the block. Clean the cables up real good. Might clean up other connections
 
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