OMC Cobra Engine Grounds

[oldOMC]

Iboat,

I'm rebuilding a 1993 OMC Cobra 5.8L engine. I'd like to know where are the grounds attached to the engine. Also, how do I test start this engine before I put it back in the boat. The harness is fully attached. Also, is there any specific order as to how the split lock washer and tooth lock washer are placed? Any input is appreciated!

Below are some pictures. Pardon the funny lighting. Are these the appropriate spots?

 

[jaxnjil]

Re: OMC Cobra Engine Grounds

i dont have an omc but the points you have shown are ones mercruiser uses. you should be fine

 

[twostroke87]

Re: OMC Cobra Engine Grounds

The easiest way to start an I/O on the ground is to make a switch with 2 wires that run from the positive side of a good battery, to the + side of the coil, when the switch is on it will power the coil and the engine will have spark.

Make sure not to forget and leave it on after you are done, you can blow your coil that way.

Make sure that the engine block is grounded in one or both of the spots you've pictured above.

Make a jump switch or jump the starter with a screw driver to turn it over.

If you are only running for a short period. (IE less than a couple mins) You can leave off the water. If you plan on running it for a while stick a hose into the water intake tube.

To turn the engine off, flip the switch or disconnect the wire that you have running to the coil.

Be sure than the motor is secure and stable where it sits, it will vibrate and shake being that it is not mounted down, make sure its not going to hurt you or damage itself.

Oh yea make sure you have some gas hooked up, be in a well ventalated area, don't let the exhaust build up.

Keep a fire extinguisher handy, if this get out of hand or it is doing something you don't like remember all you have to do is cut power to the wire running from the battery to coil. If for some chance that this does not work, choke the engine to death by cutting off its air, in severe "run away engine" situations, where you cannot block off the air well enough. Fire your extinguisher into the carb until it shuts down. Avoid this if you can though, you will be rebuilding your carb and cleaning your intake.

Have fun!

 

[KRH1326]

Re: OMC Cobra Engine Grounds

Nice Job On The Rebuild.

I fabbed a steel set of artificial stringers to run my engine. I ran it off and on for the last half of the winter that I rebuilt it, to run it in some before throwing it in the drink.

I made a slideshow, and you can see the setup in the last half of it.

If you want to see it, you have to go to the link and actually hit the blue download button, then watch it in media player or something. If you just watch the preview on the site, it gets cut short and it's crappy quality.

http://www.4shared.com/file/122755283/a64be221/JesseRae-_Boat.html

Good Luck!!!

 

[bruceb58]

Re: OMC Cobra Engine Grounds

I would attach the grounds to the side of the block where you can easily get at them. If those points are easily accessible when the engine is in the boat, that is fine but it looks like they might be trouble since they are at the rear of the motor.

 

[mcleaves]

Re: OMC Cobra Engine Grounds

Where you have the grounds is the stock location on my OMC 302.

Once the engine is installed though it's pretty tough to clean them up annually as I do during my commissioning process. I moved them to the front of the block for better access. I If and when there is salt water in the bilge it's in the back too. Any wires I can get away from there I do.

Also makes it a shorter run to the batts

 

[oldOMC]

Re: OMC Cobra Engine Grounds

Thank you all so much. Your replies were really helpful

I'll update when I try it out.

 

[mcleaves]

Re: OMC Cobra Engine Grounds

Hope she runs as nice as she looks!

 

[JustJason]

Re: OMC Cobra Engine Grounds

a ground is a ground.... if you have any doubts about it, do a resistance check, but more importanty, a voltage drop test when the engine is cranking to verify wether you have a good ground or not.

 

[oldOMC]

Re: OMC Cobra Engine Grounds

twstrokes87, Today I was so eager to start my rebuilt but it failed to start. It turned nicely with a fresh battery, at first I thought it did not get gas but
Upon reviewing your directions I realized that I did not connect the the + side of the battery to the + side of the coil. I assumed that the harness being connected would do the trick. I will try again tomorrow. thanks

 

[oldOMC]

Re: OMC Cobra Engine Grounds

I have tried to start the engine again today making a switch with 2 wires that run from the + side of the coil to the battery but again the engine was turning on the slow side but it did not start. The battery got weak and will be recharging it. I know it has gas but i doubt it gives sparks as I tried with a spark light tester nothing was visible How do I test if the coil is good? Any advice is very much appreciated.

 

[oldOMC]

Re: OMC Cobra Engine Grounds

coil tested ok, I have good sparks in each plug, got gas , engine turns ok but battery gets weak after few tries, at times starter goes dead completely but after a while by disconnecting and reconnecting everything it cranks again.
1. what causes the starter to stop working (especially after a spark) ?
2.how do I check fot a votage drop or resistance check?
Thanks in advance to all the good people in this forum.

 

[oldOMC]

Re: OMC Cobra Engine Grounds

engine started up like a bullet after opening up the choke.


thanks!