Mercury 50hp not starting

[Tnorred80]

I just bought a boat with a 50hp mercury motor with thunderbolt starter, serial number is 6419539. Motor is cranking good, carbs seem to be clean but I am not seeing spark when I pull a plug and test it against the housing. can anyone help with the year and possibly have any suggestions on the spark issue?

 

[vegasvinnie]

I would get the manual for your boat. I did and it helped with all the issues so far. I'm still working through some issues but the manual is a great help. Look through the troubleshooting area and it will probably lead you to the problem. Was boat running when you bought it and it's just now having the issue or did they not show you it running?

 

[Tnorred80]

The engine would not start when I bought it, the previous owner said it had problems starting cold. Now I am not seeing spark when I try and turn it over.

 

[Tnorred80]

Update.....
I replaced the trigger switch because I noticed corroded and fraying wires, still no spark. I found a chart with some info to test for and here is what I have found

Test red to red/ white wires on switch- 83.8 ohms, 38 vac
Test blue to blue/ white wires on switch- 5.54 K ohms, 202 vac

I am going try and replace the stator next due to the ohms being so far off on the blue wires. Let me know if anyone has any suggestions on pointers if I might be going the wrong way on this.


​Thanks

 

[Redwing4900]

I have that same motor it looks like my serial number is 1050625...I say that because I type in your serial number at the link below and that the result was a few hundred different. I would actually go in a different direction. I would try to see if what's under the flywheel is doing what its supposed to be doing before you spend anymore money. Can you remove the flywheel and clean up the connections under there? Of course the shop manual will be a better resource than me. I had to go to a Mercury marine dealer to find out my motor was a 1984 vintage. I suspect yours is too. Is it a 4 cylinder? Mine is. I'm not sure why Mercury's are such a mystery for the year they were made, and all of that. I also am finding it difficult to match the other components with my motor in the shop manual as the serial number ranges are not matching up with the equipment that should be included for carburetors, etc. Oh well what I do know is that this motor runs very well for me and should do the same for you with a little work I hope.

 

[Tnorred80]

Update.......
I found out from Mercury that it is actually an 83, 4cyl. I replaced the switch box and it is now running great. I appreciate everyones comments.

 

[Redwing4900]

What led you to the switch box? I'm just curious because I found out that I am not getting spark on cylinder #2 of my motor. I figured it was a bad switch box since that is the first line that the coil connects to, but the manual says to change the stator and doesn't tell me how to troubleshoot for the switchbox. The stator is $185 while the switchbox is $215. Your previous post said you were going to change out the stator...did you do that first and then the switchbox? Is there a way to test the switchbox for ohms or voltage so you know that's what it is? Just curious. Thanks for the info.

 

[Tnorred80]

I did not replace the stator even though it did not test exactly to specs due to the fact that I was getting good voltage to the switch box. I decided to do the switch box first because I found a good deal on ebay for the part, only $120. Here is the link to the website where I found the specs for the components to test. Hope this helps.

http://www.cdielectronics.com/produ...2a2-332-5772a3-332-5772a5-332-5772a7-9-25104/