Mercruiser 1997 5.7 Weak Spark

[achris]

Re: Mercruiser 1997 5.7 Weak Spark

ok here it is.
I changed all new spark plugs and engine started for about a minute. I think now there is a problem with my timing and carburetor. I can not start the engine again now but at least there is a spark.
One more thing. I put my old distributor sensor back and it works ;-)
I rebuild my carb today so I will try again in the morning. I will keep you all posted.

One of my troubleshooting principles at play there... If it's all getting weird and nothing makes sense.. Put it all back to original and start again... 9 times out of 10 you'll find parts you have condemned are actually ok....

Anyway, great job :thumb:... Good luck with the carb work and, as always, please let us know how it works out... (We really are interested)

Chris.......

 

[sophieb]

Re: Mercruiser 1997 5.7 Weak Spark

I finaly got some time so I went on the boat. After moving my distributor engine started and ran but it would die after I gave it some throttle.Also when I checked with timing light it looked to me that white line was off as I moved distributor it would change position before and after 0 mark. It is weird. could it be my carb that needs some cleaning? I had the distributor out of the block could I put it in 180 opposite? would the engine start with that?> thanks

 

[achris]

Re: Mercruiser 1997 5.7 Weak Spark

If the distributor was in 180 degrees out, no the engine would not run...

As this is Thunderbolt V you need to time the engine by the procedure in the book, you can't do it like an old car. They is a wire you need to ground, then set the timing, then remove the grounding link.... Do you have the manual with the correct timing procedure in it?

Chris.....

 

[sophieb]

Re: Mercruiser 1997 5.7 Weak Spark

No I do not Chris. Can it be found somewere on the web? Thanks. I know about the purple/white wire. Is it the one close to the front of the engine? I have one with rubber plug and female connector.

 

[sophieb]

Re: Mercruiser 1997 5.7 Weak Spark

I think I found it:
Mercruiser Marine Engine Timing Procedures | Performance Product Technologies

Also one more question. I do not have any plate that shows 0 or any other degrees for the timing on the block. All I have is a white line on the main pulley and 2 plastic bumps that have a little line between them on the block. I will take a picture today and post it here.

 

[achris]

Re: Mercruiser 1997 5.7 Weak Spark

No I do not Chris. Can it be found somewere on the web? Thanks. I know about the purple/white wire. Is it the one close to the front of the engine? I have one with rubber plug and female connector.

Initial timing for your engine should be 10?BTDC... Idle speed, 600 rpm

 

[sophieb]

Re: Mercruiser 1997 5.7 Weak Spark

nd it works. my starter died from all that cranking so I purchased new one today and it all runs like the clock. I have a timing light with the advance and it is very helpfull. thanks for all halp guys and specialy Chris.

 

[achris]

Re: Mercruiser 1997 5.7 Weak Spark

Happy to hear it's all good... :thumb:

 

[sophieb]

Re: Mercruiser 1997 5.7 Weak Spark

Hello Chris,

one more question about timing. Should I have 10 degrees at 650 rpm at idle or at 2000rpm?
from reading other articles online I understand that Thunderbolt V has advanced timing that runs as I explained previously. Is this right? Thank you.

 

[achris]

Re: Mercruiser 1997 5.7 Weak Spark

Your engine needs to be timed at 10 degrees at 650 rpm (which is idle)....

If you'd like a full write up on the TB-V, PM me with your email address and I'll send you some 'light' :facepalm: bedtime reading....

Chris.......

EDIT: it fits here, So.....

 

[sophieb]

Re: Mercruiser 1997 5.7 Weak Spark

Very helpfull. Thank you. Does my ignition have a knock sensor as well? I only have one box at the distributor.

 

[achris]

Re: Mercruiser 1997 5.7 Weak Spark

The only TB-V engines without knock sensors were the 5 litre and the 5.7L (the 5.7LX did have). And since you have a 5.7L, then no, you don't have a knock sensor...

 

[sophieb]

Re: Mercruiser 1997 5.7 Weak Spark

Thank you.

 

[sophieb]

Re: Mercruiser 1997 5.7 Weak Spark

Hi Chris,

I am back. I took the boat out today and after 15 minutes started running rough and than died. after couple of minutes it restarted again for a few minutes but died again and I had to be towed back. Any idea what could be the problem? I am thinking that could be a fuel problem( carburetor) when it gets hot it maybe leaks air or so. Thanks

 

[achris]

Re: Mercruiser 1997 5.7 Weak Spark

Did you happen to check to see if you had spark? It could be a heat problem with the ignition system, or a fuel problem. You need to isolate which one before we start looking at fixing...

Chris......

 

[sophieb]

Re: Mercruiser 1997 5.7 Weak Spark

I heard engine knocking when I advanced throttle.

 

[achris]

Re: Mercruiser 1997 5.7 Weak Spark

When you say 'knocking', are you referring to ignition knock, like pinging..? If so, knock the timing back a couple of degrees.

Chris...

 

[sophieb]

Re: Mercruiser 1997 5.7 Weak Spark

Not sure how to describe it. I would say more like tap tap tap and then engine died. Something like valve knocking? I wish I had it on video.