Help!!! No spark on 50hp thunderbolt mercury

ryvesy · 23 June 2010, 06:37

JUST BOUGHT A QUICKSILVER control box that im trying to wire up to a 50hp mercury thunderbolt
have not conected any wire to the blue terminal on the swich box and still have no spark?the mercury switch is disconected
have checked with a meter and found that the blue wire is down to earth is this right?
ANY HELP WOULD BE SOUND CHEERS

9D280 · 23 June 2010, 08:13

As I donlt have a wiring diagram to hand, I'm going to have to talk you through some checks, without the wire colours!

I assume you have an oldschool pull start machone, and it;s a nice new control box? (Thunderbolt even predates my lump of ooil burning joy)

So, check one. Will it start with the control box unplugged? If yes, then problem's in the box.

Assuming you find it's the box. and assuming the box is a lot more modern than the engine, this is where you need to check the pins literally one by one & fins out what pin of the connector is attatched to what inside the control box. If you have a box with a key switch for the 'leccy start, the "off" position is essentially another deadman switch, so check that's working OK (or insert key & put to "run" position).

For a wiring diagram, try googling it, or this as a start http://forums.iboats.com/showthread.php?t=407283 There's a link with a note as to what to click on.

ryvesy · 23 June 2010, 11:51

its an electric start have no spark could it be the control switch?we have no eternal wires connected to this so it should spark?cheers

9D280 · 23 June 2010, 14:17

OK, if electric start, is it cranking OK and does the choke solenoid click when you hit the choke button? IF all of them are working, it's time to disconnect the deadman & the ket switch & do a continutity check with the varios combos of "off" / run & "deadman in / out". The other bit of electrickery in the control box is a microswitch to disconnect the wire to the starter solenoid when in gear It's open circuit unless it's in neutral, but shouldnlt stop the engine running, just stop the starter turning.

My thoughts here are that if you have a nice new box, they may have changed the pin configuration in the plug, so your deadman is now connected to the tacho signal wire or something equally daft.

Test 2: remove the cowl, unplug the remotes, and try to start it on the emergency pull start / manual choke. If it starts, then you'll definetly know it's a problem in the control box. To stop, (in this case), plug your remotes in! As you say, in the absense of a deadman switch, it should spark.

As a tangent thought, did you replace the control box 'coz the old one was mechanically gubbed? If so, there's an argument for doing a wiring swap and take the old electrics and put them in the new box. (or do what I did, remove all the electrics from the old control box (apart from the anti start in gear switch, which a suitable length of 2 core wire and 4 crimp connectors will fix), and fit the ignition switch & deadman to the console.

Nos4r2 · 23 June 2010, 14:35

First, what model thunderbolt ignition is it? There's 2 types on a blueband 50. One is a belt driven dizzy, the other looks like a normal CDI with coils.

Have you got the mercury tilt switch on the right way up? It's behind the front panel of the cowl with a single wire going into it. Looks like a tiny black box with 1 screw holding it on.

Once you've identified the mercury switch it gets easier as it's part of the kill circuit. Remove it and check for continuity to earth with a multimeter, then trace it along, unplugging things and testing for continuity to earth in the direction of the main loom'til you don't have continuity. The last thing you unplug will be your problem.

ryvesy · 23 June 2010, 17:16

think its the belt drive dizzy
could it be the switch box?

Nos4r2 · 23 June 2010, 17:43

Quote:

Originally Posted by ryvesy

think its the belt drive dizzy
could it be the switch box?

Do what I just told you and report back...

ryvesy · 23 June 2010, 18:57

my mates doing the wiring for me,will be back on the case 2morro,should i send you a pm when he,s done the checks what you,ve given,cheers james

Nos4r2 · 23 June 2010, 21:32

Quote:

Originally Posted by ryvesy

my mates doing the wiring for me,will be back on the case 2morro,should i send you a pm when he,s done the checks what you,ve given,cheers james

That's the most basic way of faultfinding the kill circuit on those motors I can type out, so it should work.