Mercruiser 5.0 no power to fuel pump when ignition ON

[Franco_boater]

Hello,
Im writing this post in the name of my friend from the same marina.
He said he was boating with his family then heared a pop and the motor dies...
I suspect also no charging because his batteries are drained too...
When he keys the ignititon ON the pump doesnt work we cannot hear the sound of fuel pump for a while, there is also no power to the electric choke (yellow-red wire). The starter works, it kicks so I assume 120Amp is OK.
Are there any other fuses there somewhere? Its 1998/9 5.0L Mercruiser

Ciao!

 

[Fun Times]

Do you get 12v at the helm gauges when you turn the key on?
Do you have a test light or multimeter handy as well.

There should be a 50-amp circuit breaker with a red button up on the engine, also possibly a white 90-amp fuse right at the starter post where the battery cable connects, plus a 20-amp breaker or fuse right near the ignition key switch plus maybe some other fuses like a fuse box panel for other accessories under/behind the helm where the gauges would be.

 

[Franco_boater]

Yes I have multimeter ready, I need to sneak around I couldn't find any more CB's around... thanks!
For sure there is 120Amp at the + at the starter but I assume its OK if the engine cranks?

 

[Franco_boater]

Can You tell me please how to check/bypass oil switch to eliminate the problem?? Thanks!

 

[Fun Times]

Yes I have multimeter ready, I need to sneak around I couldn't find any more CB's around... thanks!
For sure there is 120Amp at the + at the starter but I assume its OK if the engine cranks?

Unless the fuse at the starter has been changed from original size for whatever reason then the amps should be 90 from new... The 50amp breaker is item number 22 while the 90 is (would had been) one of the item numbers 20

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Again number 8 at the starter shows it as 90 here too,

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oops edit: forgot to ask, we are working on a carbureted engine vs fuel injected? If EFI, then the oil psi switch and info below doesn't apply as it doesn't have an oil switch to power the fuel pump.... < That would be relays that need checking...

Item 11 will be the oil psi switch down by the oil filter location... Port rear lower side. It's powered first by the engine starter while cranking over then once running, the alternator/purple wire which is the ignition side takes over... Which is why the gauge's having power was mentioned above?

https://shortcircuitweb.com/mercruiser-oil-pressure-switch-wiring/

But yes, if the engine cranks over then the 90 ought to be good... To know best once there, check for 12v right at the orange wire at the back of the alternator...Find the 50-amp breaker and check both sides for 12v....With the key left on, wiggle the wiring harness especially if the gauges don't power up. Check the back side of the key switch for 12v and see if it gives the purple wire power when switched to on.... also physically move the safety lanyard switch to make sure it's not halfway in the off position.

 

[Franco_boater]

Yes it’s carb, ok I’ll get back when we will be at the boat.
I don’t remember if the gauges were alive when keyed on. I’ll check that.
For sure the engine was cranking a little until batteries die, and also there was continuous beep ( I assume because of no oil pressure )

 

[Bt Doctur]

What are the first 3 lette

Yes I have multimeter ready, I need to sneak around I couldn't find any more CB's around... thanks!
For sure there is 120Amp at the + at the starter but I assume its OK if the engine cranks?

rs of the word "ASSume"
The main battery cable is direct to the starter, no fuse there.
The 90a white plastic fuse was supposed to only protect the alt but they added the main system to it. When it blows you lose the alt and main system feed.
I remove the red system wire from it and wire directly to the main solenoid post. Your sill protected by the 50A CB

No fuel pump power until you have engine oil pressure

 

[Franco_boater]

Thanks I’ll check that fuse too