75 Merc 1150 thunderbolt no spark

[chigger]

trying to start this engine before spending alot of money on it. Bought the manual and did all the tests available without having the special tools for the trigger, coil and switchbox. Can anyone tell me, should the green wire from the switchbox that go's to the coil be energized when the keyswitch is turned on? I know it's not an old chevy, but thats more my speed in automotive "fixens". </font></li><br />[*]<font size="2" face="Verdana, Arial"> web page

 

[12Footer]

Re: 75 Merc 1150 thunderbolt no spark

Greetings, Chigger, and welcome to iboats. That is a destributer model with twin 3-cylinder switboxes?

 

[12Footer]

Re: 75 Merc 1150 thunderbolt no spark

If so, (I think it is the distributor equipped..the green going to the coils is the ampilified pulse to the coils.They are green,green/red, green/yellow, ect.<br />The Black with yellow stripe is grounded to kill the engine, and should be disconnected at the switchbox to test kill switchand it's wire circuit for short to ground.<br />NOTE: You'll have no way of shutting the engine down if you disconnect this wire and regain spark, so have fuel disconnected during crank-test with t5his lead floating.<br />On older Mercs, this kill wire is ORANGE.

 

[chigger]

Re: 75 Merc 1150 thunderbolt no spark

thanks for the response, this is a distributor model with only one switchbox, not the twin. also has only one coil instead of the models that have multiple coils. serial # is 3954672. also this coil is what they call red or orange in color, not black which i read somewhere may be different. really appreciate all reply's

 

[12Footer]

Re: 75 Merc 1150 thunderbolt no spark

Ok. I guess the info so far is generic enough.<br />Something else you might check....Merc used this waterproofing goo around the base of some of thier distributors,and it's like a clear tar. It runs down over the years,and 'glue' the rotor to the inside of the cap,stopping it cold, and stripping it out. and can pool inside the distributor cap.Remove the cap, and with one finger (do not force it), try to turn the rotor. If it turns, that is your problem. On the earlier models (not sure about the single box engines), the rotor is not repalaceable, and the entire sub-assembly must be replaced! Dangol engineers!<br />But they tended to strip out at the distrib shaft and the plastic rotor's base. I was tempted to use marine tex or JB-Weld on them, but don't like pushing fate at sea...Still, i'll bet it would werk.While in there, make sure the timing belt up under the flywheel is still in one piece. They rarely break, but can.

 

[KIWI MERCMAN]

Re: 75 Merc 1150 thunderbolt no spark

chigger <br />Not very offen you will have a coil problem on that model no matter what colour they are, It is a 12 v system, and if my memory serves me the green wire will only get voltage from the switch box if it is triggered. The white wire to the 4 wire side of the switch should have 12v when you turn your key on.Again if my memory is right we used to take a spark tester and put direct to coil and hook up a pulsar box to the switch box to trigger it. This took the place of the engines trigger, if you got spark then your trigger is no good, if not then your switch box is the problem.<br />You need to find one of these pulsar boxes. <br />Maybe your local dealer can help with this.<br /><br />Hope this helps.<br />Kiwi

 

[chigger]

Re: 75 Merc 1150 thunderbolt no spark

Thanks to both of you. 12Footer, the rotor is solid on shaft as designed, turns when cranking engine so timing belt is still there. alligned timing mark up to check piston location at t.d.c. Have rewired complete engine harness (positively correctly) and cleaned all grounds.<br />KIWI, Hi from the U.S., On the four wire side of the switchbox, both red & white wires have 12V. to them.Also, wire from other side of box has voltage going to distributor. Kill switch has been tested and functions properly. I'm not familiar with a pulsar box...Perhaps known as something else here. Appreciate the help from both of you. Maybe dealer will extend some free info More like $65.00 per hr. <br />Belooking for your replys.