Starter issue mercury 40 hp 2 stroke

[Justinehammer]

Hi all.

I bought a boat this summer and have had issues since I bought it. I have had issues with the electrical and ignition and can't seem to find the culprit. I had it to the boat shop and they couldn't figure it out.

First, when starting, the engine runs and then dies. Sometimes the starter will get stuck engaged and then I have to hit it a little or disconnect the battery. Replaced the starter solenoid, didn't have that issue for a while,but boat would still run and then die. It would run as long as throttle was forward but when put in neutral, it would die. Then I had the carbs cleaned. Boat ran after that and started fine but ran at very low power and when throttle pushed forward all the way it would die out. So I replaced the fuel filter and added more premium gas. Then tried to start it and had the starter get stuck engaged a couple times. Got it unstuck. Then the last time I turned the key over it wouldn't stop trying to start up even after I pulled the key out. So I unplugged the battery. Now when I hook up negative terminal on battery, the engine tries to engage. Even tried disconnecting the ignition switch and kill switch and it still tried to engage. So it is currently unhooked and I am trying to figure out what the issue is.

 

[SteveVT]

Sounds like multiple separate issues:

Bad ignition switch, bad solenoid, or a starter wiring short to positive, will keep the starter RUNNING (meaning powered, not just stuck engaged). with the ignition switch off. Even new solenoids can go bad.

Test: remove the small start signal wire (not the small grounded wire) from the solenoid and check it with a voltmeter (or 12V test light) to ground. If the ignition switch is off, there should be no continuity. If the switch is on, also no continuity. If the ignition switch is in the START position, then there should be continuity. Any other results, replace the switch. However if all are correct, replace the solenoid (again).

Bad starter motor return spring or starter motor attachment misalignment will keep the starter motor engaged with the flywheel ring gear but starter won't be actually running (meaning NOT powered). In other words just mechanically stuck in the extended position and being driven by the flywheel. In the case of misalignment, make sure starter bolts are tight, or if the spring is sticking or broken, replace the starter.

Motor dying with full throttle usually means fuel delivery problems. Suspect the fuel pump and/or the carb high speed jet. Yes even though the carb was recently cleaned -- if you have degrading fuel hose or dirt in tank these could immediately clog the carb main jet again.

Ethanol eats the inside of ol\d fuel lines, and they can still look good on the outside, but be flaking off on the inside. Replace old lines with new ethanol compatible lines. Check that the tank is clean, and that any internal fuel filter in the tank (and engine) is not clogged

If the carb was recently thoroughly cleaned and re-gasketed throughout, one quicker way of cleaning the main jet, short of full disassembly, is to just remove the float bowl nut -- this actually contains the high speed jet,..... and cleaning that with carb cleaner and a blast of compressed air. You will probably have to remove the carb to access this nut, but that's less work than fully disassembling the carb.

This jet cleaning will do no good however if the lines and tank still pass debris to the carb.

Have the fuel pump and vaccuum lines (if any) checked. If you gently squeeze the fuel bulb when it starts to die, does that keep the motor running?

Do a spark test -- and also with an insulated puller, alternately pull the plug wires off, first one, then the other cylinder while idling. There should be an RPM drop for each. If no drop for one, and stall for the other, possible coil, plug, or spark wire problems for the non-firing cylinder.

.

 

[Justinehammer]

So I replaced the starter solenoid again and that fixed the sticking issue. I did take some fuel out and there are small specs of black stuff in it. Replaced the fuel line and bulb. Also took the carbs back off and cleaned them again and there were small specs in there too. Then replaced the spark plugs as the other ones flooded out. Then find out that the bottom spark plug isn't working properly, getting full of black stuff which I think may be why the engine won't run in idle. There is spark though so that's not the issue. When I spray carb cleaner in the bottom carb it doesn't respond so it's not operating with the other two. Lots of black sut gets thrown out of propeller area when ran. When throttling the engine, it seems to speed up and bog out on its own without moving the handle. Squeezing the bulb does not change anything either. Cannot get to tank as it's built in. Did put new gas and seafoam in. Not sure where to go from here, maybe it's the cdi or the stator?

 

[SteveVT]

1. First find the source of all the black stuff before trying to solve anything else. You cannot troubleshoot if your carbs continue to get debris. If the source is an internal tank, you have to deal with that somehow, or you will never progress to a working engine.

2.) Seafoam will just complicate all your issues since it will release more contaminants, particularly deposits in a dirty tank, since you added it to fuel. Seafoam cannot remove rubber or plastic debris in a carburetor from deteriorated hoses and fittings. In fact it will deteriorate them further. It's a heavy duty solvent. It's really pointless to use with the problems you are having.

3.) Effective troubleshooting requires an orderly progression. Start first with getting clean fuel to the engine. Get rid of all the Seafoam. Clean your carbs again after you're sure no more dirt can get to them. Then when you are sure you have clean fuel delivery, you can move on to ignition troubleshooting.