1972 /20HP Mercury tiller NO SPARK HELP!!!!

[Fudoshin]

I inherited my grandpas 1972 baracuda 14' boat with a 1972 Mercury 20HP motor on it. My aunt said they used it two summers ago and it worked fine. So I was about to go out on the lake yesterday for the first time and I tried the motor and it didn't start. It did sound like it arced a bit or there was some sort of spark at first. When I took the cap off there was a mouse nest in there and the ground wires had visual damage to them which I hear is normal for those older wires, (cheap and corroded fast) A bad ground wire wouldn't prevent it from turning over would it? I am not too familiar with boat motors so I am looking for any advice. I went to a local marine mechanic and he said this year mercury had an ignition module that is notorious for going bad and that's probably the problem. What should I start with first? He hooked it up and said there was no spark when I pulled the cord. I just don't want to spend a ton of money if it's an easy fix.

Thanks

 

[JMichael]

I'd say the first thing you need to do is to repair or replace all the wires with bad or damaged insulation and then see where you are with regards to spark and starting.

 

[drum]

hi Fudoshin, my thought is if you replace your bad wires first, you could save money that way, and some wrench turners ,
will name a part that cost a lot and bill you the small stuff on top of it. so if you do have little experance with cars it might help.
and save you some money and do the work, take some pics. and refer to them for help.

 

[Fudoshin]

Jmichael that's what I was thinking as well, and drum, I'm pretty good with cars, and engines in general and I'm mechanically inclined, I just haven't worked on too many boat motors, I have a mercury 75 (7.5hp) that I replaced the coils, carb, plugs, and pull rope myself, I have a mercury TM manual so I should be able to figure it out. I just thought that since I do not have a ton of experience with these motors that I would try and get some advice. I appreciate everyone's input. I just hope I can get things running. The guy I went to to ask about the motor is 83 years old and has dealt Mercury and worked on boat motors since 1963 so I thought he'd be a good person to go to instead of these corporate boat companies. I will do as much as I can myself and then go from there. I'll take some pics if I have more questions in the future.

 

[JMichael]

With yours being a 72 model, you have a pretty basic points/condenser ignition system. I have a 75 model of the same motor and it has the Thunderbolt ignition switch box which I think is the part your mechanic was referring to when he said they fail frequently. So I don't think you will have to do too much to get yours back up and running.

 

[sawmill]

Is this motor electric start? If so it needs to be in neutral to start and I think the manual start also needs to be in neutral. I would replace the wires before I do anything else.

 

[JMichael]

Is this motor electric start? If so it needs to be in neutral to start and I think the manual start also needs to be in neutral. I would replace the wires before I do anything else.

I think the neutral start is only applicable on this motor if you have remote start. I know mine doesn't have a neutral switch built in to the motor but some of the mercruise remote controls have them internally.

 

[Fudoshin]

No it is not electric start, this has a ignition module I believe instead of a stator, and the switch is in neutral as well as the tiller gear in the start position. I haven't taken the top portion of the motor off which exposes the fly wheel, I saw two ground wires that were for sure crumbled/chewed, the guy hooked up a spark test to the plug insert holes and said there was nothing coming out, so do you think I should start with the plug wires, reg wire harness, and then check the ohms on the coils?

 

[JMichael]

No it is not electric start, this has a ignition module I believe instead of a stator, and the switch is in neutral as well as the tiller gear in the start position. I haven't taken the top portion of the motor off which exposes the fly wheel, I saw two ground wires that were for sure crumbled/chewed, the guy hooked up a spark test to the plug insert holes and said there was nothing coming out, so do you think I should start with the plug wires, reg wire harness, and then check the ohms on the coils?

I guess the first thing to do would be to establish what motor you have. As you think it has an ign module, that would make it a later model than the 72. Here is a parts breakdown for a 72 model and it clearly shows the stator, points, coils, etc, but no ign module. https://www.crowleymarine.com/mercury-outboard/parts/455_40.cfm
So maybe you could post the serial number of your motor so we can verify what motor you have.

 

[Fudoshin]

good call Jmichael..lol...see this is where the amateur side comes out haha serial # is 3432584, I'm only going off what the marine mechanic told me when I brought the boat to him to see if I was doing something wrong, at first he said the stator was notorious for going bad, the he said this year "72 had an ignition module, and I haven't started taking it apart yet so I didn't visually see what was under the cap.

 

[JMichael]

Well, that's a 72 model according to the serial list I referenced. The first thing I would do is check the compression. If compression is good, I'd verify if it had good spark or not. If it doesn't have good spark, then I'd repair/replace any damaged wires and install new points/condensers/plugs.

 

[Fudoshin]

Thanks for the help, I will start that process tomorrow and let you know what I find.

 

[Fudoshin]

Hey guys,

So I worked on the motor for the past two days, took apart the carb. cleaned it out good, replaced two cracked fuel lines, 4 cracked wires, ran a fuel treatment through the tank, and cleaned off the points from the spark plug wires into the coil as there was some (humidity formed) corrosion there, I'm guessing from the mouse nest that was in there when i got it. Took about 20 pulls but it started up and is running smooth. Thanks for the advice and I'm glad it's not a stator or ignition module like I originally though! Fish on people!!