Cant get mercruiser 4.3 in time!!!!!!!

6meter

Chief Petty Officer
Joined
May 15, 2010
Messages
525
Re: Cant get mercruiser 4.3 in time!!!!!!!

Have you tested the compression yet? You might have sucked a valve and it dosen't run good because of a mechanical issue, not an ignition issue.
 

Aloysius

Chief Petty Officer
Joined
Aug 21, 2010
Messages
484
Re: Cant get mercruiser 4.3 in time!!!!!!!

Kinda sounds like it jumped timing, particularly if it died when running. Not common on Chebbies, but not unheard of.
 
Joined
Sep 26, 2010
Messages
256
Re: Cant get mercruiser 4.3 in time!!!!!!!

ok let me see if i remember what everyone asked. Compression is at 150 +/- one or two psi on every cylinder. Going to check the harmonic balancer to see if it is bad and shifted. I checked tdc by removing the spark plugs and bumping the starter untill it started pushing air past my finger (on the spark plug hole) number one cylinder of course then with a screw driver through the spark plug hole turned the motor by hand untill the pistion was at the very top. then looked at the dist to see if the rotor button was pointing to where the number one on the cap sould be. im going out to see how many fingers are on the dist now ( your talking about the upside down crown looking thing attacted to the rotor button that goes through the ignition optic sensor to cut through the electro magnetic feild?
 
Joined
Sep 26, 2010
Messages
256
Re: Cant get mercruiser 4.3 in time!!!!!!!

ok checked again with a mercruiser mechanic. He said everything is good mechanical timing wise spark plug wires are good everything is good. He said it is a bad altinator killing my ignition
 
Joined
Sep 26, 2010
Messages
256
Re: Cant get mercruiser 4.3 in time!!!!!!!

yep damn sure was a bad altinator replaced the altinater and everything is good
 

Alpheus

Lieutenant Commander
Joined
Aug 3, 2009
Messages
1,757
Re: Cant get mercruiser 4.3 in time!!!!!!!

Good question. It should have started and ran without an alternator if the battery was good...
 
Joined
Sep 26, 2010
Messages
256
Re: Cant get mercruiser 4.3 in time!!!!!!!

it was drawing all the power from the coil causing a really week spark. the higher I reved the motor the more it shorted out the ignition system to the point it stalled the motor
 

EddiePetty

Lieutenant Junior Grade
Joined
Aug 25, 2008
Messages
1,008
Re: Cant get mercruiser 4.3 in time!!!!!!!

it was drawing all the power from the coil causing a really week spark. the higher I reved the motor the more it shorted out the ignition system to the point it stalled the motor

NAUGH :confused:
 

Alpheus

Lieutenant Commander
Joined
Aug 3, 2009
Messages
1,757
Re: Cant get mercruiser 4.3 in time!!!!!!!

Was the alternator still charging your battery?

How did you confirm it was bad?

What part of the alternator was bad? (diode,stator)

How did the tech test his theory?

So if someone has symptoms that mimic yours you could have them disconnect their alternator and see what happens?

I have never heard of this in car or boat. I'm curious...
 

Aloysius

Chief Petty Officer
Joined
Aug 21, 2010
Messages
484
Re: Cant get mercruiser 4.3 in time!!!!!!!

Whats the alternator got to do with timing???
 

Alpheus

Lieutenant Commander
Joined
Aug 3, 2009
Messages
1,757
Re: Cant get mercruiser 4.3 in time!!!!!!!

Exactly.

Did you check the timing after the new alternator was installed?
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Cant get mercruiser 4.3 in time!!!!!!!

Yes, low voltage will cause it to run poorly. Low voltage does that to electronic ignition systems. A low battery is also why he had starting problems. (See original post).
If the engine doesn't crank over fast enough, it won't start.
Of course, it was never mentioned that the engine didn't turn over very fast.

the higher I reved the motor the more it shorted out the ignition system

Another good example of not knowing what you are saying. NOTHING was shorting out, at higher rpm, the engine needed more voltage, but didn't have it.
 
Joined
Sep 26, 2010
Messages
256
Re: Cant get mercruiser 4.3 in time!!!!!!!

disconnected the neg battery cable and the engine died instantly but the alt would charge a tiny bit when reved up. so I thought that it was ok I havent taken the old alt to be benched tested yet but I will take it to the local auto parts store to have them test what went bad in it and more of a discription of how my alt in wired in, and what caused it.
I do know that he said this is not very common to happen but he said that I should of known if I told him that the voltage stays below 12 volts when idling. I never connected the two together, sorry if this dosent help anyone Ill try to explain better tomorrow when I get the results back from the bench test
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Cant get mercruiser 4.3 in time!!!!!!!

disconnected the neg battery cable and the engine died instantly but the alt would charge a tiny bit when reved up.

That is how you destroy alternators and electronic ignitions and electronic everything else.
 
Joined
Sep 26, 2010
Messages
256
Re: Cant get mercruiser 4.3 in time!!!!!!!

Yes, low voltage will cause it to run poorly. Low voltage does that to electronic ignition systems. A low battery is also why he had starting problems. (See original post).
If the engine doesn't crank over fast enough, it won't start.
Of course, it was never mentioned that the engine didn't turn over very fast.



Another good example of not knowing what you are saying. NOTHING was shorting out, at higher rpm, the engine needed more voltage, but didn't have it.

First off I do know what im talking about but I tend to mix words up alot because of a tramatic brain injury I sustained while serving in iraq. Dont be such an ***** and I didnt have a slow crank problem battery was fully charged at 12.4 volts. so as you said another example of not knowing what you are saying right back at you. and was kept on a charger the entire time i was trying to diagnose so I wouldnt drain the battery
 

Aloysius

Chief Petty Officer
Joined
Aug 21, 2010
Messages
484
Re: Cant get mercruiser 4.3 in time!!!!!!!

don S. is correct as usual..disconnecting the negative is a good way to destroy your electronics. WHY would anyone do that????
 

Don S

Honorary Moderator Emeritus
Joined
Aug 31, 2004
Messages
62,321
Re: Cant get mercruiser 4.3 in time!!!!!!!

and I didnt have a slow crank problem battery was fully charged at 12.4 volts. and was kept on a charger the entire time i was trying to diagnose so I wouldnt drain the battery

There is another example. 12.4 is not fully charged, and keeping it on a charger so the battery wouldn't drain is what masked the problem.

First off I do know what im talking about but I tend to mix words up alot because of a tramatic brain injury I sustained while serving in iraq. Dont be such an *****

Sorry to hear about your injury, but how am I or anyone else supposed to know that ?????? Since this is a forum, and there is only what is typed in a message, we have to assume you are saying what you believe to be true.

I just don't think it would be right to ask everyone if they have a tramatic brain injury before we get into their mechanical problem ????? I could just see how that would go.
 
Joined
Sep 26, 2010
Messages
256
Re: Cant get mercruiser 4.3 in time!!!!!!!

don S. is correct as usual..disconnecting the negative is a good way to destroy your electronics. WHY would anyone do that????

Tell that to the mercruiser certified tech at the marina that. I got tired of the issue so took it to a boat dealer to do the hard work that I couldn't figure out. If it was really bad to do then why would a certified mechanic do it?
 
Top