1988 100 hp merc no fire on bottom cylinder

[holbs10]

Hey there. Heres my problem. I have a *88 100 hp 4 cylinder merc that has had good days and bad days ever since Ive had it.<2 years> Basically Ive put a spark tester on the on all cylinders and found no juice on bottom cylinder. Great blue spark on the top three. I ended up buying a manual(solec)and it has been very helpful so far but Im a bit nervous making any rash decisions. Last year i purchased a red stator kit and thought all my problems were solved untill I installed it and still have the same issue. I now lean towards the switchbox. Ive ruled out coil buy swaping the wires with the top cylinder and I then had spark. Ive ohmed out the trigger and it fell within spec. What am I missing? Do i just go out and get the switch box at this point? Also None of my tach speedo or fuel gage work. Ive done a bit of reading on trouble shooting of the gauges but really want to get this running like it should first. ALso this is the multi meter I have. when they say to use the rx1 scale what does that mean. It refers to it in the book a lot but my meter doesnt have it. I thins what it means is if something ohms out to 400 ohms that would be 4.00? Thanks in advance. Im getting closer but not quite there yet. As for the dva to see the output of my stator as it s running that something else right?

 

[Laddies]

Re: 1988 100 hp merc no fire on bottom cylinder

No, that not a DVA just a auto ranging Ohm and volt meter anf yes because its auto ranging your getting that reading, my meter can be locked to the range you choose but I don't see anyway to do that on yours but it looks like a good meter.

 

[holbs10]

Re: 1988 100 hp merc no fire on bottom cylinder

So can I use this to check voltage or will it blow up?(the meter) As far as what Ive said so far what would you recommend me to check?

 

[Laddies]

Re: 1988 100 hp merc no fire on bottom cylinder

Yes you can check voltage thats what the AC and DC volt scales are for but it will not work as a DVA a DVA can fe hooked between your meter and the voltage source but without the adapter it won't work. Your ign. system is AC voltage and a DVA capture the peak voltage reading in the system.

 

[halmc]

Re: 1988 100 hp merc no fire on bottom cylinder

ALso this is the multi meter I have. when they say to use the rx1 scale what does that mean. It refers to it in the book a lot but my meter doesnt have it. I thins what it means is if something ohms out to 400 ohms that would be 4.00?

on the RX1 scale a multimeter reads in actual ohms w/o any multiplier. I see that your meter doesn't have an RX1 scale, but I'll bet that the little diode icon is in fact an RX1 scale. Thus if you measure the resistance of something that reads 4.00, I think that means it's four ohms.

 

[holbs10]

Re: 1988 100 hp merc no fire on bottom cylinder

Is it possible for a bad key switch to cause any problems Im having right now. Also I had to un plug the low oil warning beeper when i got the boat cause it always beeped. mY book doesnt tell me how to test the key switch. Any info?

 

[holbs10]

Re: 1988 100 hp merc no fire on bottom cylinder

Time to update. Great news. I bought the new switch box and I have beautiful spark on all cylinders now! Feeling the motor and spark plugs I can tell that all cylinders are firing. The only question i have is why are they all firing if I only have it idleing. The bottom two really shouldnt be firing since I havnt hit above 2000 rpm. It maybe possible that its burning off all the gas I pumped into it by sqeezing the bulb or that fact that it hasnt run right for a long time and its just burning all the old fuel left in that bottom cylinder. Im a bit optimistic in thinking Ive solved my problem since I wont be able to find open water for a while still. It has to be fixed though, I started with no spark on bottom cylinder and now I have great spark. Also check battery while the boat was running and it seems to be charging perfectly 14-15 volts. Tach still doesnt work but that will need to be trouble shot. Thanks everyone for your help, I sure hope to have this thing perfect for the upcoming bass tourneys!

 

[boatinnjax]

Re: 1988 100 hp merc no fire on bottom cylinder

All the plugs fire throughout the RPM range, the bottom two cylinders do not always get enough fuel to sustain ignition and compression until you advance the throttle.

 

[holbs10]

Re: 1988 100 hp merc no fire on bottom cylinder

All the plugs fire throughout the RPM range, the bottom two cylinders do not always get enough fuel to sustain ignition and compression until you advance the throttle.

Thanks, I know that. What Im mean is I unpluged the top plug wires and I could get the boat to run just off the bottom cylinders but I think it was just leftover fuel in those carbs . All I know is I cant wait to get back on the water. Still ice everywhere but Sebago Lake!

 

[hkeiner]

Re: 1988 100 hp merc no fire on bottom cylinder

Tach still doesnt work but that will need to be trouble shot.

The below links contains some troubleshooting guidance that may be of help to you.

http://ww2.tflx.com/pdf/obtach~1.pdf

 

[holbs10]

Re: 1988 100 hp merc no fire on bottom cylinder

The below links contains some troubleshooting guidance that may be of help to you.

http://ww2.tflx.com/pdf/obtach~1.pdf

Thank you very much. That is so helpful. This will help me out greatly.much more than my solec book did.

 

[holbs10]

Re: 1988 100 hp merc no fire on bottom cylinder

Took boat out and it hammers down again. Would never had done it without the search button on this site and the help of all of you here.Great forum!