1995b force 120hp no spark on all cylinders after it runs awhile

Boat runs great until you run it awhile and stop for awhile to fish for an hour or so then it will not start, i posted this on here before and was told that it may be flooding and to rebuild fuel pump so i did and it still did the same thing so i rebuilt carbs and tested yesterday except this time i took spark tester with me. I rode up the lake about 5 miles ran better than it ever had cause when i rebuilt carbs i noticed one carb shutter was not closing all the way and both was not opening all the way and man what a difference it made on take off to have full throttle it has been like that since i bought it new, also does 50 mph now instead of 46 mph, any way when i slowed down to turn around to come back it died like you turned the key off and would not start so i checked for spark and did not have any on all cylinders. i started looking at harness wires but did not see anything wrong and checked spark again and had spark. drove the five miles back to landing at different speeds no problem ran like new. got to landing cut off and fished for 30 to 45 mins and guess what no spark again. never got it to spark so i trolled to landing and loaded it up. i get up this morning and it has got spark. I was hoping it didn't so i could check the yellow and black cut off switch wire. I cheked compression all cylinders have 120 psi. I hope this post is not to long trying to give you all the info i can. Boat looks and runs like new i really want to fix it please help. IMAG0027 | Flickr - Photo Sharing!

Re: 1995b force 120hp no spark on all cylinders after it runs awhile

Do you have a picture of the ignition system? Need to know if it is the Thunderbolt system that uses the switch box, or the Thunderbolt CDM ignition system. Most likely uses the switchbox but need to be sure.

Re: 1995b force 120hp no spark on all cylinders after it runs awhile

Switch box. heres some pictures 1. IMAG0004 | Flickr - Photo Sharing!

2. http://www.flickr.com/photos/100731583@N03/9586351258/lightbox/

Re: 1995b force 120hp no spark on all cylinders after it runs awhile

While you have it at your place, check all of the ground connections. The case of the switch box itself needs to be making good contact with the mounting plate that it's attached to. There should also be a ground wire that goes from the switch box and coil mounting plate to the engine block.

If it dies on you again while you're out on the water, disconnect the Black/Yellow wire from the switch box. If that fixes it, then either your Kill Switch, or wiring may have a problem. If no affect, then the problem is somewhere else.

Check the wires that come out from under the flywheel (trigger and stator). Make sure the insulation on them has not rubbed off from touching the flywheel or the block and shorting to ground.

I have to say though recently I've run into several motors with intermittent spark that have the Mercury Thunderbolt switch box ignition. Seems as though when the switch box gets hot, they stop working. Unfortunately it's kind of pricey, so you want to eliminate everything else that you can before you go that route.

Re: 1995b force 120hp no spark on all cylinders after it runs awhile

pnwboat said:

While you have it at your place, check all of the ground connections. The case of the switch box itself needs to be making good contact with the mounting plate that it's attached to. There should also be a ground wire that goes from the switch box and coil mounting plate to the engine block.

If it dies on you again while you're out on the water, disconnect the Black/Yellow wire from the switch box. If that fixes it, then either your Kill Switch, or wiring may have a problem. If no affect, then the problem is somewhere else.


Check the wires that come out from under the flywheel (trigger and stator). Make sure the insulation on them has not rubbed off from touching the flywheel or the block and shorting to ground.

I have to say though recently I've run into several motors with intermittent spark that have the Mercury Thunderbolt switch box ignition. Seems as though when the switch box gets hot, they stop working. Unfortunately it's kind of pricey, so you want to eliminate everything else that you can before you go that route.

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Ok i went out there and tightened all wires on switch box and grounds. and found the wires are deteriated here is video

VIDEO0004 | Flickr - Photo Sharing!

Re: 1995b force 120hp no spark on all cylinders after it runs awhile

That's a new one. Never seen mushy insulation on the wires before. As long as it's not allowing the metal conductor inside to poke through and touch something that it's not supposed to, I guess it might be OK. Only way to correct it is to replace the wiring, or the component with wires. Looks like some of those mushy wires..... Red and Red/White, Blue and Blue/White are your stator wires.

Disconnect the stator wires and read the resistance. Red to Red/White should be 75 - 90 Ohms. Blue to Blue/White should be 3250 - 3650 OHMs. That stator has a low speed winding and a high speed winding. Can't remember which is which Red or Blue, but if the low speed winding is bad or going bad, you will have problems starting as the spark will be weak or gone at cranking speed. Also make sure the six magnets that are epoxied under the inner circumference of the fly wheel are all there and intact. Not broken or missing.

Re: 1995b force 120hp no spark on all cylinders after it runs awhile

pnwboat said:

That's a new one. Never seen mushy insulation on the wires before. As long as it's not allowing the metal conductor inside to poke through and touch something that it's not supposed to, I guess it might be OK. Only way to correct it is to replace the wiring, or the component with wires. Looks like some of those mushy wires..... Red and Red/White, Blue and Blue/White are your stator wires.



Disconnect the stator wires and read the resistance. Red to Red/White should be 75 - 90 Ohms. Blue to Blue/White should be 3250 - 3650 OHMs. That stator has a low speed winding and a high speed winding. Can't remember which is which Red or Blue, but if the low speed winding is bad or going bad, you will have problems starting as the spark will be weak or gone at cranking speed. Also make sure the six magnets that are epoxied under the inner circumference of the fly wheel are all there and intact. Not broken or missing.

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yes they are all sator wires. the other wires seem ok , they harden up away from switch box only last inch or so is bad. how bout taping them up the last inch with electrical tape? if magnets was missing would it still run like new?

Re: 1995b force 120hp no spark on all cylinders after it runs awhile

Probably OK to use electrical tape. If you could get some heat shrink, that would be better, but anything is probably better than nothing.

If one of the magnets was missing, it probably wouldn't run that well. If it's broken and a piece missing or has come unglued depending on how it's sitting, it may run fine sometimes. It's always a good idea to look up underneath the flywheel and take a peek at the magnets when you're having ignition system issues. It'll be pretty obvious if one is out of whack.

Re: 1995b force 120hp no spark on all cylinders after it runs awhile

pnwboat said:

Probably OK to use electrical tape. If you could get some heat shrink, that would be better, but anything is probably better than nothing.

If one of the magnets was missing, it probably wouldn't run that well. If it's broken and a piece missing or has come unglued depending on how it's sitting, it may run fine sometimes. It's always a good idea to look up underneath the flywheel and take a peek at the magnets when you're having ignition system issues. It'll be pretty obvious if one is out of whack.

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I took it to lake and ran great stoped and fished and cranked up and started back to landing went to idle speed at a bridge and it just died . Wouldn't crank. I checked spark and none on all cylinders unhooked black and yellow still no spark used trolling motor to get back to landing and loaded it up took it a 2 miles 2 storage and checked spark again and none.. hopefully it want have spark when I take it to the shop and they can figure it out.