Loss of Power

[whitnes10]

Hey there,
So this is an interesting one. At the end of last summer I was having starting problems with my 1979 70hpm Mercury Thunderbolt. Had my cousin down to help problem solve if it was just the need for a new starter, which we did figure out I need. The new problem that happened came from our last attempt to bypass the starter with jumper cables where we lost all power. I'm assuming we shorted something somewhere accidentally. But when we try and turn the key over, there is nothing, not even a click. Battery is brand new so that's not the issue. Just wondering if anyone has some helpful insight here as how to troubleshoot where the loss of power is from. We are possibly thinking in the control box, but aren't sure and plan to start working on the motor in the coming weeks.

Any help would be great. Hoping to get this back up and running for the summer.....

 

[Mohawkmtrs]

Bypass the starter??...or the solenoid?

Look for a blown fuse and recheck your connections (and cleanliness) all the way from the battery to the starter.

Got a serial #?

 

[merc850]

It could be the starter solenoid is not grounded by wire or it has failed, it should click when the key is turned. Use a voltmeter to see if there's 12v across the small terminals - if not the key or wiring is broken. Also the shifter may not be in full N move the lever fore and aft slightly while the key is held on start. There is no fuse on this model.

 

[garbageguy]

Hey there,
...Battery is brand new so that's not the issue...

you've probably checked it, but even brand new batteries can be junk - before going too far, suggest verifying the easiest stuff

 

[whitnes10]

Thanks all. Yes before storing it for the winter, we checked and confirmed the battery. With better details on what we did, was we connected the jumper cables to the battery, then grounded out one end and touch the positive end directly to the starter (see link for the look of our starter: https://www.amazon.com/Starter-Mercury-Outboard-50-65436-50-66015/dp/B003IDCNXS).

By doing this we bypassed any issue between the control unit and the starter. But with this bypass and a full strong battery, there was not enough torque to turn over the flywheel. So we figured that it was in all likeliness the starter that was the issue, especially since it is still the original one. When we did this one more time, that's when we lost all power.

I believe that we checked the ground on the starter to the motor, but I'll keep that in mind. We haven't used the voltage meter yet, but will make sure to check that too.

But there is no fuse that we need to worry about? What about in the control box anything there? We are just kind of learning about this engine as we go, because no one around our area is will to work on this old of an engine.

 

[Mercurylips]

Can't understand a Marine Mechanic that will not work on a vintage motor. There are still parts for it and not impossible to troubleshoot. The switch box needs to be checked out with a multi meter as would your other electricals. Just sounds to me that you are suspecting the correct area of concern. I have had similar problems with nothing more than a poor battery cable connection.

 

[racerone]

Some will argue.---But take the starter apart for inspection and an ohm test from commutator to the shaft.----Costs no money and is easy to do.

 

[whitnes10]

Yeah we took it into a local dealer a few years ago, and they basically wouldn't do much other than a couple of things, then they tried to upsell me on a newer engine. Didn't like dealing with them, so then I found a backyard guy who was awesome, replaced my entire lower unit with a refurbished lower unit and it was great!

Been having starting issues over the last couple of summers, and each summer I actually did take the starter off and cleaned the brushings and it helped both times. But I think the magnets are getting weak, which is what's causing my starting issues.

I will definitely try all of these ideas when we get back at it, whether we've tried them or not. Once I get power back, my plan is to purchase an aftermarket starter from ebay or amazon, and give that a go.

Thanks all and if there are any other suggestions, please let me know. I'm no mechanic, but have been working at this for a few years and have learned on the spot and have been able to keep it running pretty well given my lack of knowledge, so I plan to get it back into action this summer!

 

[racerone]

I doubt that the magnets are getting weak !