Mercury Thunderbolt Blueband 850 No spark

[wee mac]

I have a mercury thunderbolt 850 blueband engine. I am having some problems with the startimg of it. I have used it all season and 90% of the times she starts no problem 1st turn of the key. I put the muff on the rear leg and it started no problem. Took it out to the lake yesterday and it constantly turned over and would not start. She eventually started for approx 10 seconds and cut out again. Took it home and checked all wires ect to see if ther was any loose connections they are all tight. I took plugs out to clean them and heated them with a blow torch. Put them bak in and boat fired up again for approx another 10 seconds and died again. I dont think its getting proper spark. Anyone any ideas or suggestions.

Many thanks.

 

[Chris1956]

Re: Mercury Thunderbolt Blueband 850 No spark

Gee, use a timing light to take a spark test. That motor have a battery powered ign system and distributor, or ADI with four coils?

 

[wee mac]

Re: Mercury Thunderbolt Blueband 850 No spark

Thanks for reply Chris

It is battery powerd ignition and distributor.. I will give that a go and see how i get on. I just find it weird that 90% of the time it starts 1st go no problem.

 

[Chris1956]

Re: Mercury Thunderbolt Blueband 850 No spark

The wiring goes bad on those motors. Look for shorts and broken wires.

 

[wee mac]

Re: Mercury Thunderbolt Blueband 850 No spark

Checked all the wires ther now. No shorts or cuts. Waiting on new plugs to come. Could it just be possible that the plugs is just completly nakered.

 

[Chris1956]

Re: Mercury Thunderbolt Blueband 850 No spark

Well, That motor should have gapless plugs. They last a real long time....Check the spark plug wires for resistance from cap to spring end. it should be zero. The rotor is not removeable and real fragile. Check the carbon electrode in the cap. Clean the cap. Watch for arcing from plug wire to ground.

 

[wee mac]

Re: Mercury Thunderbolt Blueband 850 No spark

Well, That motor should have gapless plugs. They last a real long time....Check the spark plug wires for resistance from cap to spring end. it should be zero. The rotor is not removeable and real fragile. Check the carbon electrode in the cap. Clean the cap. Watch for arcing from plug wire to ground.

Yea they are gapless plugs, god only knows when they were last changed so ill change them for a pieces of mind.

Will check the plug wires for restistance tomoro when im home from work and let you no how i get on.

Have the carbon electrode in the cap and all cleaned.

 

[big dog 347]

Re: Mercury Thunderbolt Blueband 850 No spark

I'm new two the boating world and newer to the old merc outboards, but I have had some two stroke sleds in the past. I had one sled that eat plugs up it would run great and all of a sudden it would start misfiring and quit running. I would put new plugs in it and be back to normal. its worth a set of plugs at a couple of dollars a piece.

 

[wee mac]

Re: Mercury Thunderbolt Blueband 850 No spark

Ok so new spark plugs have arrived. Still no spark. I have more than 9.5volts while cranking at the white wire on the switchbox, and more than 9.5volts on the brown wire on the opposite side of the switchbox. Ive read up that im meant to have over 100volts while cranking at the coil/green wore i have nothing.... :-/ i have also checked plug wires with the buzzer part of the multi-meter and they are all buzzing fine.

Any help much appreciated.
Thanks

 

[wee mac]

Re: Mercury Thunderbolt Blueband 850 No spark

Another quick pointer could any tell me were thr kill switch/ deadman switch is and if i can bypass it to see if i can get spark.

Is the mercury switch amything to do with this...

Thanks again.

 

[Chris1956]

Re: Mercury Thunderbolt Blueband 850 No spark

The mercury switch will kill the spark. Disconnect it.

The CDIElectronics web site has a test to see if all the ign components are good, except the trigger. You might run it. It will prove your wiring, coil and switchbox are good.

 

[wee mac]

Re: Mercury Thunderbolt Blueband 850 No spark

Okay folks here is the latest after long hours of testing and checking wires.

I no power/volts coming from the green on the switch box to the coil so
I would imagine this is why I have no spark... correct??

Outcome buy a new switch box or is there any way that i can test the box
if not were would be the best place to buy 1.

thanks for all help sofar folks.

 

[Chris1956]

Re: Mercury Thunderbolt Blueband 850 No spark

You will not normally see voltage on the green wire. This is not a battery/coil ignition. Run the bloody CDIElectronics web site test, and it will tell you if the switchbox and wiring are good. It is a simple test...

 

[wee mac]

Re: Mercury Thunderbolt Blueband 850 No spark

Sorry for not posting any sooner was away on holidays.

Ordered a brand new switchbox before i went and it arrived this morning..

Went to the garage this morning and fitted the new switchbox and bang 1st turn of the key she went.

Checked all spark plugs great spark.

Thanks every1 who took the time to reply to my topic post. Thanks for all you help.

Cheers