1973 Merc 500 partial rebuild-carbs, impeller, plug wires, starter-can't get started

[Sctrj]

First time boat buyer - believed the guy. The "mid-90s" motor was 1973. Before I did anything the, the motor ran on hose water (not in lake yet), but stalled often. Pulled carbs off and rebuilt. FULL of crud. New filter, new gaskets. I also pulled and rebuilt the plug wires. After I put back together, the motor turn over and ran like a dream; changed gears, idled well, no issues. The pee hose never sprayed water. I decided to rebuild the water pump. No problem. After I put lower unit back on, the motor started right away, then stalled. Turned over again, then stalled. Boat contact told me "water in the carbs". So, I pulled all the stuff off the back ( you know how much it takes to get to those carbs on the '73) drained the carbs, drained the fuel lines. Put everything back. Now would not turn over at all. I found out that I had pulled the cable from the coil ignition assembly. Fixed that issue, started right up and stalled. Same thing a few times. I put it in gear after it started a few time and it ran great until back in idle. Decided to adjust the idle screw. As instructed by manual, I counted the turns when I rebuilt the carbs. They were 1/2 turn out. Searching around I saw that 1 1/2 turns was a good baseline. I adjusted to 1 1/2 out. After putting back together, I cannot get the motor to turn over at all. FYI - I also replaced the fuel tank to a plastic one. I am all out of ideas. Any suggestions would be helpful.

 

[DeepCMark58A]

Did you rebuild the fuel pump?

 

[Sctrj]

Not yet. That is something I thought about. But, with so many other ins and outs that have happened. Would that keep the motor from turning over at all?

 

[60sboater]

It won't turn over or won't start?

 

[Sctrj]

Sorry. The starter works great. Fly wheel spins. Will not start....anymore.

 

[60sboater]

Squirt some fuel into the carbs and see if it starts.

 

[Sctrj]

OK, Tried squirting fuel in carbs while starting. Nothing happening. Starter and flywheel spin. Not even a flicker of engine firing. Thinking about pulling plug wires off spark plugs and testing if there is any spark. Any other ideas?

 

[Sctrj]

I tested the spark at the spark plug. Nothing. Then tested at the inginition coil. Didn't have the spark wire in the ignition coil enough. Re-sat the wire. Tried to star the engine. This time it coughed. The nothing. Not even a cough. Pulled the wire, put on a clean connector, re-sat. Tested the spark plug spark. Was present on all plugs now. But, still cannot get the engine to run. No cough, just starter and flywheel spinning. What in the world. Any ideas? Fuel is getting to the carbs.

 

[UKMike]

Sounds like you have a ground somewhere, does it have an emergency cut off switch or a tilt switch? Often the tilt switches go and often are removed because of this. Sounds like something is grounding on that side of the ignition.

 

[UKMike]

Get one of those spark testers that clip outside the ignition wire and then you will know if it's electrical or fuel when turning over the motor.

 

[Sctrj]

No Title

No tilt on this motor. Sitting on a pontoon. There is a kill switch. One this to note, which may be the issue,... the wire harness has been cut and re-wired with clips. There was some corosion right where the wires were coming out. Could this cause the issue? One wire was open. I wire brushed the corrosion off, then wire taped the wire.

I wil look for an ignition spark tester. Only have a spark plug type tester.

 

[UKMike]

Possible you have dislodged something in the wiring, if the harness or connections were corroded they will likely be the same somewhere else. Try starting the engine at night with the cowling off and see if you see any sparks and make a note of where they are, then check them out in the light, or as I said get a spark tester, they are cheap on ebay, only a few $.
You need to go back to basics, start with spark, if you get a good constant spark you know it is fuel related, if you don't get a constant spark on all cylinders and in the right order you know its electric. I had a similar issue which took me months and a few hundred $ to sort out and it turned out to be the stater and trigger unit! Had similar issues as you so start on the basics.

 

[UKMike]

If you have a timing light you could use that to test for spark with the plugs in.

 

[Sctrj]

OK, this is weird. I waited until it was dark to see any sparks when starting. I am at the engine, wife on starter. No choke. Fires right up. Great idle. Forward, throttle, back to neutral. Still purring. Reverse, throttle, neutral. Still purring. Shut off. Turn on...no choke. Same test, forward, neutral, reverse, neutral. No issues. Shut off. Try to start w/ choke. WIll not start. Try to start w/o choke. Starts right up. What in the world? Any ideas?

No wires sparks seen when starting amongst the harness of any other connections.

Next question, if I have the hose to the water pee thingy unattached, with no water coming out, is that a big issue? I did replace the impeller.

 

[UKMike]

A few things here, so you must have an issue with the choke or pre fuel, but if you try the same in the day without the choke and your motor runs OK then research the choke issue, or maybe your engine is correctly configured? Re: the Pee hole, depending on the engine model, some pee out straight away and others don't. The thermostats should control the water flow inline with the poppet valve "if on engine". If the engine runs for 3 minutes on idle with no water coming out the pee I would make sure you put the impeller and locater key in correctly... Also make sure you put the flow plate up the right way in the WP

Don't run your engine with no water flow, Never ever!!

If you don't need choke, do use it

 

[Sctrj]

Impeller and key are in place correctly. I ran boat on lake for about 30 minutes, ran great, no pee. I have pulled the lower unit off again and tried to squirt water from pipe that goes into the water pump, and also in to the exit hose after I pulled off the pee jet. I cannot get water to go in/out the other. I have no idea what is up. I would think this is a big issue and don't want the motor to overheat.