Merc 3.0 has no spark

[r_snowrider]

I am having troubles starting my 3.0 merc. I don't seem to be getting any spark. Does anyone know of some things I can do, or check for, before I try to replace a part? Also, what are the most common causes for not producing a spark? Thank you very much for your help, Ryan

 

[Fishermark]

Re: Merc 3.0 has no spark

what are the most common causes for not producing a spark?

If you have points, that's where I would put my money. Either clean them, or better yet, replace them and I suspect your spark problem is solved. (Then go out and buy the Pertronix kit to replace your points for good and be done with it! )

 

[hoot]

Re: Merc 3.0 has no spark

easy thing to do is pull plug wire, hold with insulated pliers, get end of wire close to spark plug, and crank engine. watch for spark to jump across to plug. if none, chek your safety kill switch, points, condensor, dist cap, ignition coil or module. if spark, then fuel side. hit the throttle level and see if a stream of gas is injected into the carb.

 

[r_snowrider]

Re: Merc 3.0 has no spark

Thanks for your help guys. I don't know a whole lot about the ignition system. Where exactly are the points. Also where is the safety kill switch.

 

[r_snowrider]

Re: Merc 3.0 has no spark

Thanks for the info fellas. I have narrowed it down to a bad coil. I'm not getting any power to the plugs. So I checked the points in the distributor, they looked fine. So then I moved on to see if I was getting power out of the coil (using the shock therapy method), again no spark. So I checked to see if the wires connected to the + side of the coil were getting power, I got a reading of a little over 12v, so they were working. I don't have a safety kill switch, atleast I can't find it anywhere. So I guess it would be a bad coil. Gonna go get one tomorrow. I'll let you know if it works.

 

[oxbowman]

Re: Merc 3.0 has no spark

Make sure your outdrive is down before checking for spark. If the drive is up you won't get spark. Before you run out and buy a coil, I would disconnect any wires off the - (neg) side of the coil except for the pigtail wire to the distributor. Turn the key on and check to see if you have spark to the points by touching in between the points with a screwdriver. You should have spark. If not, check to see if there is any bare insulation on the pigtail wire that is shorting out. You could also put a 12 volt test light on the end of the pigtail wire where it connects to the points to see if your have power. If you have power your problem is in the distributor. Points are shorted or bad condensor. If you have spark after disconnecting other wire off neg side, check to see if you have a faulty interruper switch. Good Luck. Let us know how you make out.

 

[Don S]

Re: Merc 3.0 has no spark

If the drive is up you won't get spark.

Never heard that before, please explain. There is nothing designed into the ignition system to prevent it, and I have seen a lot of people start and run engines with the drive up.

 

[Haut Medoc]

Re: Merc 3.0 has no spark

 

[oxbowman]

Re: Merc 3.0 has no spark

I have an older mercruiser with a 120 4 cyl. If the outdrive is in the trailer up position (not the trim up position) the motor will not turn over. That is the same reason you have a trim limit switch. So the outdrive will not go up beyond a certain point where you would lose the support of the gimbal ring.

 

[Don S]

Re: Merc 3.0 has no spark

What is the unit that stops spark, and now cranking an engine when it's tilted up?<br />There has to be an electrical switch of some sort to stop power for spark and cranking if what you are saying is fact.<br />I would also imagine these things would go bad once in a while and cause a no start and no crank condition. It must be a he11 of a unit, cause they never seem to go bad, there is no part number or name for the thing, it doesn't show up in parts manuals, service manuals, service bulletins and no one has ever complained about one being bad.<br />And to think I thought the trim limit was to keep you from trimming the drive to high and causing the prop to cavitate and get prop burn.

 

[DHPMARINE]

Re: Merc 3.0 has no spark

Well Don,I guess we just don't know these older drives as well as we tell people on these boards we do.The new guys are taking over.And they sure seem to jump right in and I gotta admit they got the answers.<br /><br />Obviously Mercruiser put this switch in so that people wouldn't run with their drives tilted up ruining their ujoints.<br /><br />Gotta love them Mercruiser guys.<br /><br />Hope the new guys do explain this new/old system to an oldie like me.I'll write it down if I don't<br />remember.<br /><br />DHP

 

[DHPMARINE]

Re: Merc 3.0 has no spark

rider,can you tell what you have done so far ? No spark can be lots of things,even a misadjusted interupter shift switch.<br /><br />DHP

 

[oxbowman]

Re: Merc 3.0 has no spark

Hey, you old guys sure know how to welcome newcomers to this forum! My intent was to try to help r snowrider. I don't know why you guys are upset? If it doesn't matter if the outdrive is up or down what I told him to do will help him find his problem and could save him time and money buying a coil. I'm sure you old guys remember the 3 button trim panel? You know, the one that is marked UP, UP/OUT AND IN. It had a trim limit switch, some were above the bell housing up in the gimbal housing area. You would push the up/out button to trim and the limit switch would keep you from going out past the gimbal support guides. Now, when you wanted to trailer, you would push the up botton and the up/out button at the same time to bring the drive to the full up position(trailer). Now, that is the position my boat is in when it will not start! Now, I am sorry that I did "jump right in". See, I thought that was what this forum was about. Helping others. I guess I did help out, I got DHPMARINE to offer snowrider a suggestion. I hope there are no hard feelings, and you old guys will forgive a new (old) guy. It won't happen again. Have a good day.

 

[waterone1@aol.com]

Re: Merc 3.0 has no spark

Next, I suppose it also shuts off the fuel when the drive is up ? Snowrider, did I read your post correctly that you held onto the coil output wire to see if you had spark ?? Please don't do that again, we're here to fix broken boats not heart attacks ! Looking at parts (such as points) are a very preliminary part of troubleshooting, and really doesn't do much other than verify they are there. You already verified that you have +12V on the positive side of the coil, thats good. The points switch the negative side of the coil, they "turn on and off" as the distributer rotates. when the points are open, you should have zero volts across the coil, when the points are closed you should have 12 volts across the coil. The other wire that is connected to the negative side of the coil is the shift interupter switch. This wire should not be at ground unless you are shifting the outdrive out of gear.The easy way to eliminate it from the equation is to remove that wire from the coil and crank the engine, if you now have spark, then see why that switch is sticking. By the way, could you please post the year of your engine?

 

[Haut Medoc]

Re: Merc 3.0 has no spark

There is no relation to trimming up your drive and a "no spark condition". While some of the 'newcomers/old farts' can get a little "crotchety" they do offer very solid advice...Post your year/make and model and I'm sure they/us/ me will try to help you to figure it out. This is a great forum, and you will not find any better answers anywhere without spending large $$$.Welcome to iboats. It really doesn't get much better than this. Hang in there and we'll "git 'er done'...J

 

[chrisg]

Re: Merc 3.0 has no spark

Did you check the emergency shut off switch? Make sure it is in the on position? That solved the problem I had with no spark.

 

[vipzach]

Re: Merc 3.0 has no spark

2 things to point out.<br />1) Are we sure he even has points? There is no mention of a year (unless I missed it), Maybe when he said he looked at them, he took off the cap and looked at the contacts in there. Just wondering.<br />2) Oxbowman, a tilt kill switch sounds very strange and none of us have never heard or seen one. I don't think anybosy is trying to bash at you, just trying to figure out what you are talking about. Don and many others have been around boats a long time and aren't wrong on here very often, but all we can do is guess at a problem by how it is described.

 

[r_snowrider]

Re: Merc 3.0 has no spark

Thanks for the help guys. I didn't mean to start a war. I will consider all of your advice. When I held the wire coming of the coil to feel for spark, I used one hand as to not pass the current through my chest. I have tried a few things to test the coil. I held a screwdrive between the points to see if I could get the spark to jump even a small gap, and to my surprise it would. But only a small gap, not near enough to jump the gap on a plug. But that eleminates the possibility of there being a cutoff switch being tripped. I took off the grey wire from the (-) side of the coil, still the engine would not start. It just seems as if everything points to the coil. So that leaves me with the question that if a coil is going out, will it still produce some power, even if only enough to jump a small gap? Or does it go out all together, no middle ground? Because that may explain the boat cutting out on the water when it would start. Also, waterone says that I should be getting 12v across the coil when the points connect, but I was not aware that 12v could jump a gap, I thought it took several thousand volts, isn't that the reason for the coil in the first place? And the reason it doesn't kill you when you come into contact with it is because it has a real low amperage after passing through the coil? I'm not positive but I think the coil basically trades the high amperage 12v from the alternator or battery and converts it to the high voltage that jumps the gap. But the wattage stays the same (current x voltage = total power output) Thanks for all the help fellas. I appreciate your help. Ryan

 

[r_snowrider]

Re: Merc 3.0 has no spark

Also, I am not sure of the year. It is my gf's families boat and I don't even think they know the year. But I believe it is a mid 80's marlin.

 

[gmcjohnny]

Re: Merc 3.0 has no spark

lets see trim motor up an no ignition what happens when you run aground you trim up an drive off not trim up an motor dies if you guys are not certified techs please don't say things like that thanks johnny