No spark?? Replaced a ton of stuff and won't start

[sliber0508]

Hey guys. I am at my wits end with this boat. Need advice. The boat will not start. Just cranks and cranks. I replaced the coil, points, condensor, spark plugs, and had the carb rebuilt. I got a small, inconsistent spark from the coil, it was small and not everytime I tested it. If anyone has any idea, please let me know. I feel like I tried everything, but could be missing something simple. I also can not find a wiring diagram of this engine. Serial number OB711840.

1987 mercrusier MCM 165
3.7L 224 cid.

Thank you for your time,
Stephen

 

[alldodge]

I got a small, inconsistent spark from the coil, it was small and not everytime I tested it. If anyone has any idea, please let me know.

Do you know how to adjust the points?

 

[sliber0508]

Yes, from my friends telling me and doing research. At the end of the points, where it opens, I took a gauge and have it set at .018. I'm going to double check the setting and also check again for good spark, but have to look up how to check for spark again. My buddy tested last time and got some spark, but small.

 

[alldodge]

First remove the distributor cap and look at the points. Have someone help if need be but you want to crank the motor over and watch to see if the points open and close as it rotates. The points must close not just open. If the distributor is loose, rotate the distributor a bit by hand to see if the points open/close.

Use a voltmeter at test for 12V on the + side of the coil when motor is Cranking. .Should have at least 9V with key just in the ON position

To check for spark, remove the coil wire and attach it to another spark plug. Hold the side of the plug tight against a clean spot on the block. Crank the motor over to see if you get a white or blue spark

 

[sliber0508]

I really appreciate the help. I had little over 5 volts with the key on, I tested that earlier. I am going to do the other tests this evening and I will post what I found. Also, would a low battery cause this issue? I have an old battery. Measures 12 volts but lot of cranking wore it down. It's on charge now and I may leave it on charge when trying to start, but is it possible for the battery to cause it? Eventually after cranking, it'll turn slower and slower....battery has 2013 on it.

 

[alldodge]

Yes, a weak battery will have some issues but depends on how low. A fully changed lead acid battery should read 12.7V and when they get to 12.2V and its 60%

 

[Scott Danforth]

best links are in the stickies at the top of the forum. https://forums.iboats.com/forum/engi...rch-version-of

read links 18, 19, and 20

inconsistant spark is from corroded contacts. even new points need filing

take your wife or girl friends nail file or a piece of folded sand paper, file the points a bit. then gap to somewhere between 0.014 and 0.018, hook up dwell meter, crank motor and read dwell. adjust as required. once dwell is set, install rotor and cap, then fire up the motor and set the timing.

 

[Maclin]

The description of the points setting was kind of vague, the part of the points that rubs on the center lobe must be on a flat. Then set the opening. The batt may be low but it just seems like the dwell is way off, that is what the gap on the points controls as the distributor moves.

 

[poconojoe]

Not to insult your intelligence...but when you set the gap on the points, was the rubbing block on the points resting on the high part of the cam lobe of the distributor shaft? When you stated "on the flat" I wasn't sure if you meant the high spot. A very basic thing that came to mind....just checking. Sometimes we overlook the basics.

 

[Bt Doctur]

https://www.bing.com/videos/search?...E84BC4BFE49FD9D8EF03E84BC4BFE49FD9D&FORM=VIRE

 

[Maclin]

poconojoe I meant on the high part of the lobe, totally bad post wording, ouch.

 

[poconojoe]

poconojoe I meant on the high part of the lobe, totally bad post wording, ouch.

OK, just making sure...

 

[sliber0508]

Hey guys, it was set on the low part of the shaft and you can't insult my intelligence. I know very little bout this setup and honestly not even sure what the dwell is. Also, when installing new plugs, they were never gapped. could this be the issue and does anyone know the gap for it? 87 mercrusier MCM 165 3.7L on the engine it's rubbed off. all I can see is 2 of the 3 numbers. .0?2. Thank you all.

 

[Maclin]

Spark plug gap is probably .035