Mercruiser 5.7L distributor sensor question

tfret

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I'm just going over things on my 1984 5.7 Mercruiser just prepping for Spring. I noticed inside the distributor the advance sensor is rusty looking. I tried to remove it for cleaning but it appears the shaft must be removed before the sensor can be taken out. I'm just wondering if the sensor needs replaced. I have been experiencing a bad hesitation problem for two seasons that I've been unable to solve. Could this be the culprit?DSC09327.jpgDSC09328.jpg
 

tfret

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Re: Mercruiser 5.7L distributor sensor question

BTW what am I doing wrong that my pictures insert in the middle of my text???
 

Don S

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Re: Mercruiser 5.7L distributor sensor question

Just remove the two outer screws to get the module out. No reason to pull the shaft.

As far as picture location, that is controlled by where you have the cursor.
Space bar and the enter keys put spaces between them or one above the other.
 

tfret

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Re: Mercruiser 5.7L distributor sensor question

Don, How do I know if it should be replaced?
 

Don S

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Re: Mercruiser 5.7L distributor sensor question

If it doesn't work, replace it.
 

tfret

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Re: Mercruiser 5.7L distributor sensor question

is it obvious when the sensor fails, like the engine just doesn't run worth a flip, or are the symptom's more subtle? The only problem I have is a bad stumble upon hole shot when taking off, especially if pulling up a skier. So how do I know if the sensor is bad?
 

achris

More fish than mountain goat
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Re: Mercruiser 5.7L distributor sensor question

I'm just going over things on my 1984 5.7 Mercruiser just prepping for Spring. I noticed inside the distributor the advance sensor is rusty looking. I tried to remove it for cleaning but it appears the shaft must be removed before the sensor can be taken out. I'm just wondering if the sensor needs replaced. I have been experiencing a bad hesitation problem for two seasons that I've been unable to solve. Could this be the culprit?

View attachment 190108View attachment 190109

That sensor, and the plate it's on, do not move, they are fixed. All the ignition advancing is done in the amplifier. If you have a hesitation on hard acceleration, but less so on gentle throttle advance, than I would suspect the carburetor accelerator pump....

That sensor does look sad, but they generally have two modes, working and not working. When they are not working, the engine does not run, period....

Chris........
 

Scott Danforth

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Re: Mercruiser 5.7L distributor sensor question

when the sensor goes, there is no spark. without spark, there is no bang. without bang, the engine doesnt run.
 

achris

More fish than mountain goat
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Re: Mercruiser 5.7L distributor sensor question

when the sensor goes, there is no spark. without spark, there is no bang. without bang, the engine doesnt run.

Trust you to simplify things... :D :D :D
 

tfret

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Re: Mercruiser 5.7L distributor sensor question

that's the answer I was looking for! Thanks guys.
 

bonzoscott

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Re: Mercruiser 5.7L distributor sensor question

Hesitation: achris stated accelerator pump, look down the carb while pumping the throttle checking for a good squirt with each pump. If it is squirting good, may be the ESA or cable adjustment.
 

tfret

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Re: Mercruiser 5.7L distributor sensor question

I get two healthy streams of fuel when I push the accelrator piston down, or when I push the throttle, so I'm guessing the accelerator pump is okay. Bonzoscott, what is the "ESA or cable adjustment" that you mentioned?
 

tfret

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Re: Mercruiser 5.7L distributor sensor question

A forrum search for ESA comes up empty.
 

akorcovelos

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Re: Mercruiser 5.7L distributor sensor question

That sensor looks pretty rough, I would replace it either way. Cheap way to avoid a tow in the future, ask me how I know...
 

bonzoscott

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Re: Mercruiser 5.7L distributor sensor question

It's a switch next to the carb. Look at the videos. It interrupts the spark so the drive can shift. It has wires to it. It could be failing and need replaced, but you need to try proper adjustment of the cables first. Search the forum or get a manual for cable adjustment as I can not elaborate on that.
https://www.youtube.com/watch?v=6-0l9lWKGUo
https://www.youtube.com/watch?v=vLE_tMJfSFk
 

KevinCasey

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Re: Mercruiser 5.7L distributor sensor question

I noticed this thread may also address my problem. The old sensor in the pictures looks like my old one. My boat runs I just thought as ugly as it was I should replace it so I bought a new sensor and it has 3 wires compared to my old one with 2. I have the bullet connectors and the instructions say just plug them in. It mentioned nothing about what to do with the black wire. When I did I didn't know what to do with the black wire and so I just made sure it wasn't touching anything and the boat won't start with the new one. The order is reversed on the order the rotor wheel passes the two wires. The wht/red is female and wht/green male like the old one.

Thanks in advance for any help.

Sorry if I reposted my question
 

Don S

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Re: Mercruiser 5.7L distributor sensor question

Welcome to iboats Kevin, it's always best to start your own thread with your questions. It gets really confusing when two people are asking about two different boats in the same thread.
 

KevinCasey

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Re: Mercruiser 5.7L distributor sensor question

Welcome to iboats Kevin, it's always best to start your own thread with your questions. It gets really confusing when two people are asking about two different boats in the same thread.

Don

Okay, will do.
Sorry

Kevin
 

NHGuy

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Re: Mercruiser 5.7L distributor sensor question

On your hesitation can you roll on the throttle gradually and get to full speed? And if you snap to wide open does it start to go then hesitate? If so there might be a different carb issue.
 
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