No Spark 1972 80 Hp

[bcspanky]

Hi everyone I,m back with a few questions about my 1972 80hp Thuderbolt ignition with no spark. I have made sure all wires are new with a new wiring harness, new switch box (?) the guy said it was new. and I have the old one to. New rectifier (cdi) and a new coil all of this stuff the guy I bought the boat from said he bought all of these things new. Now its my problem to see if I can get this motor running so I can enjoy it.

#1 The distributor was off and I put it back on and I belive it is lined up with all the marks on the flywheel, distributor, and the #1 piston TDC.
#2 All connections are clean and tight.
#3 The motor cranks over with plugs in no problem.

What to check for next.

Any help would be great and welcomed. Thanks Bob

 

[bullbat]

Re: No Spark 1972 80 Hp

is the engine firing?

 

[Laddies]

Re: No Spark 1972 80 Hp

First make sure the timing belt is not broken and here's a simple test for the system.

 

[bcspanky]

Re: No Spark 1972 80 Hp

engine is not firing

 

[bcspanky]

Re: No Spark 1972 80 Hp

Where do I get a Spark gap tester and how much are they.

 

[Laddies]

Re: No Spark 1972 80 Hp

Any auto parts store or you can turn the engine to the TDC mark on the flywheel and use a spark plug in number 1 wire instead. There is a very goog chance that the switchbox is not getting power from the key switch so check for 12 volts on the white terminal when the key is on.

 

[bullbat]

Re: No Spark 1972 80 Hp

had the same problem on my 77 1150 but it was my distibuer not sending a ground signal to the switchbox.

 

[bcspanky]

Re: No Spark 1972 80 Hp

How did you take care of it.

 

[bcspanky]

Re: No Spark 1972 80 Hp

Hi , Back to the no spark. I went out and bought a spark gap tester and I checked to see if I had 12 volts to the white lug of the switch box , with key on and a fully charged battery I had 12.68 volts to the white lug on switch box. then I tried the tester on the coil I set it at 7/16" and no spark I did it three times at different ground locations and nothing. Where do I go from here.

 

[Moody Blue]

Re: No Spark 1972 80 Hp

Did you check for 12V at the RED terminal of the switchbox? Need 12V at both terminals.

Did you follow the test procedure that Laddies included. It is an easy procedure to follow and clearly identifies what components are working and what is not. No guess work involved.

 

[bcspanky]

Re: No Spark 1972 80 Hp

I do have 12v at the red one. The procedure for the switchbox say disconnect the trigger wires I dont have a trigger on this motor will this test still work.

 

[Moody Blue]

Re: No Spark 1972 80 Hp

If you have a 1972 Merc 80hp then you do have a trigger.

What the instructions are telling you is to remove the three wires from the distributor side of the switchbox. Then follow the instructions.

 

[Laddies]

Re: No Spark 1972 80 Hp

If you really want to find the problem do the test I gave you 2 days ago and it will tell you what the problem is.

 

[bullbat]

Re: No Spark 1972 80 Hp

i had to replace the distibuter on my but they are kinda high dollar i got lucky and found a used one with cap and wires and all for 50 bucks, the way i figures it out was by luck when i was checking my wires off the distributer with a test light and hit the ground signal wire from the dis. to the switchbox and the coil fired. thats how i knew it was in the distibuter and not the switchbox

 

[bcspanky]

Re: No Spark 1972 80 Hp

Hi Had time to do the switchbox test and got a wonderful 7/16" blue spark in the tester every time I touched the one wire to the block. I will test the old switchbox this weekend to see if it had to be replaced. Thank you for this info. Now this test tells me that there is a problem from the distributor to the spark plugs somewhere in there. Where do I start do I remove the distributor and start looking in there. You guys have helped me out very much and I thank you.

 

[Laddies]

Re: No Spark 1972 80 Hp

If you have good spark when you arc it but none when tou crank the engine, you have a bad trigger. To change the disy. start by getting a manual. Just breifly you need to remove the cap, next the center bolt in the shaft that hold thes plate and drive pulley on the dist. the belt is next and the 3 nuts and bolts that attach the dist. mount to the engine block, the ground wire then drop the dist. and mount off the engine. At that point you must dissassemble the dist and mount or if you find a used dist you reinstall it and a syn and link on the engine. Heres a part breakdown to get a idea of whats involved. http://www.mercruiserparts.com/Show...desc=DISTRIBUTOR+ADAPTOR+AND+VERTICAL+LINKAGE

 

[bcspanky]

Re: No Spark 1972 80 Hp

Hi well I did all the tests and now I go to the distributor and see the trigger now is this replaceable with just the trigger or do I need to get the distributor housing that has the trigger in it or can I get just the trigger. Would this be the last faze before I see spark at my plugs. Thanks Bob