87 90 hp Mercury - No spark

harwich

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This boat has not been used for years and I am trying to getting it running again for an upcoming vacation.<br /><br />day 1- I put a new battery in pulled the engine covers and sprayed a little starting fluid into the carbs and the engine would fire up and run on the starting fluid for a few seconds. The gas cap was froze so I could not get any gas in it. I put some penetrating fluid on the gas cap and let it set overnight.<br /><br />day 2 - I get the gas cap removed and put a couple gallons of fresh gas in the tank, prime it spray in a little starting fluid, crank it and nothing. I try this several more times to no avail. Pull a plug wire and use a screwdriver to check for spark I try this on all 3 cylinders and I do not seem to be getting any spark at any of them.<br /><br />I do not know anything about the ignition system on these things. I know that there are three switch boxes and three coils. The switch boxes all have two lare wire connected at the top and two smaller wires on the bottom. The top + wire on all three shows 12 volts with the key on. With the engine turning over I show no voltage on either of the smaller wires at the bottom of the switch box.<br /><br />With the engine turning over I show no voltage to either wire on any of the coils. <br /><br />Any advise on where to go from here will be greatly appreciated.<br /><br />Thank You
 

Laddies

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Re: 87 90 hp Mercury - No spark

First stop the starter fluid while theres anything left, I have never seen a ign system like you describe on a 1987 Mercury let us have a serial number to ck the system please--Bob
 

harwich

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Re: 87 90 hp Mercury - No spark

I am probably just not describing it well.<br /><br />serial number 0B154685
 

harwich

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Re: 87 90 hp Mercury - No spark

Anyone have any advise? I posted serial number and some pics.<br /><br />Thanks<br />Steve
 

Laddies

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Re: 87 90 hp Mercury - No spark

harwich, the book say it's a 1987 90, first diconnect the blk yellow wire from the switch box to see if the problem is in the engine or wiring, there should be no voltage to the system that it does not produce if there is and the blk yellow wire is diconnected remove the red wire from the rectifier if it goes away then it's the rectifier. Let us know--Bob
 

harwich

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Re: 87 90 hp Mercury - No spark

Bob,<br /><br />Thank You. It seems to have been the mercury tilt switch. Now I have another problem, it will not shut off. Please see my new post "90 hp merc- has spark now - will not shut off. " If you have any advice I would really appreciate it.<br /><br />Thank You<br />Steve
 

harwich

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Re: 87 90 hp Mercury - No spark

Bob,<br /><br />I seem to have lost my spark again. It started running after I disconnected the tilt switch but now tonight it will not start even with that disconnected. I don't quite understand your instructions in your last post. Are you saying to remove the blk yellow wire and just check for voltage at the switch box? Sorry for being dense.<br /><br />Steve
 

harwich

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Re: 87 90 hp Mercury - No spark

I did some checking with the key on and off and I am showing 0 volts to every connection on the switch box. I tried it with mercury switch connected and disconnected. Does this tell you anything?<br /><br />Thanks<br />Steve
 

harwich

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Re: 87 90 hp Mercury - No spark

I forgot to mention that I do have 12 volts at the red wire on the rectifier. None of this tells me anything hopefully someone can give me some more guidance at this point.<br /><br />Thanks<br />Steve
 

Laddies

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Re: 87 90 hp Mercury - No spark

harwich, do you have a DVA or OHM meter if you do we can give you readings to ck the systemk
 

harwich

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Re: 87 90 hp Mercury - No spark

I have a digital volt meter that will do the ohm readings but I don't think it is capable of the peak voltage readings.<br /><br />Thanks
 

harwich

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Re: 87 90 hp Mercury - No spark

I did take some ohm readings on it the other day based on some information I found in a repair manual I picked up (Selcoe or something like that). From what I remember the reading I got on the trigger wires were ok but when I tried to test the stator I would only get a reading for a second then it would just show an open line. In fact I was pretty much convinced that the stator was bad, then read something about the mercury switch so I tried disconnecting it and it started right up. I started it about a dozen times yesterday morning and then last night when I went to work on it again I was back to the no spark problem, really confused me.<br /><br />Thanks<br />Steve
 

Laddies

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Re: 87 90 hp Mercury - No spark

Your right with out a adapter it won't, ohms are not a good but will work in most cases,<br />Flex Plate Flywheel<br />blue to grd 5800 to 7000 ohms 180+ volts<br />red to grd 135 to 165 ohms 25+ volts<br />Cast flywheel<br />blue to grd 3250 to 3650 ohms 180v<br />red to grd 75 t0 90 ohms 25+v<br />TRIGGER<br />1st brn to w/blk 2nd white to w/blk 3rd purple to w/blk all are 800 to 1400 or 4+ volts <br />If these test good, both stator and trigger you will have a bad box
 

harwich

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Re: 87 90 hp Mercury - No spark

These are probably stupid questions but.....<br />How can I tell which Fly wheel I have? Is it stamped on the fly wheel or something?<br /><br />Do I need to disconnect these wires from the switch box when I perform the tests?<br /><br />Do I do these with the key on? key off? or cranking?<br /><br />Thank You for all your help.
 

harwich

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Re: 87 90 hp Mercury - No spark

BTW Where can you pick up an adapter to do the peak readings? and any idea how much they cost?
 

Laddies

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Re: 87 90 hp Mercury - No spark

The flex plate wheel is bolted together on top,the wires need to be diconnected to ohm test, and Rapair/ CDI sells adapters that work with flute meters for around $90 list
 

harwich

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Re: 87 90 hp Mercury - No spark

Bob,<br /><br /> Can you help me save some shred of my sanity? It started right up again tonight. I got home from work and went out to perform the tests you suggested. Just for the hell of it I hit the key first, and it fired right up. I didn't prime it or choke it or move the throttle I just tapped the key and it caught instantly. Do you have any idea why it would be intermittent like this? I have a trip in a couple of weeks but I hate to take it if I never know when it is going to start.<br /><br />I greatly appreciate your assistance so far.<br />Thanks<br />Steve
 

Laddies

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Re: 87 90 hp Mercury - No spark

harwich, the system either has an open in it that can be effected by tempeture or bad connection somewhere, the other possiblity would be a bad switch, but if you have the blk/yellow disconnected then it has to be a open or bad connection
 

harwich

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Re: 87 90 hp Mercury - No spark

The blk/yellow is the same connection that connects to the mercury switch right? If so I had it removed when I initially started it tonight but then I killed the engine and re-connected the mercury switch and it still started.<br />Does that tell you anything? Any advise on trying to track down the open or bad connection?<br /><br />Thanks<br />Steve
 
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