1984 35 hp mercury outboard won't start

[rooster519]

Hey everyone. I was out about a month ago on a boat that I just bought, it's a 1984 alumacraft classic 16 with a 35 hp mercury outboard. As we were tooling up river the motor decided it was going to slowly die, almost like I throttled down and shut it off, but I didn't. It wouldn't restart for anything and had to be towed off the river. When I got it home the next day there was no fuel making it to the motor. Fixed that problem. Now it wont start. I have checked both cylinders and cylinder number 1 looks dry even though number 2 has fuel, or so it appears. If I take the plug out of number 1 cylinder the motor will run...somewhat, but with the spark plug in number 1 there it just turns over and over and over, and never shows a sign of starting. Any ideas? I haven't checked for spark yet cause I figure what good does spark do if fuel isn't there? Any help is greatly appreciated.

 

[motoman125yztb]

Re: 1984 35 hp mercury outboard won't start

Hey, I'm new to the game. I have the same motor and had the same problem. First thing you need to find spark to rule that out. You can test for a basic spark with and inline tester, or using a spare plug grounded. I would check the wires from the coil going back to the switchbox they sit very close to the flywheel and sometimes can get caught and knicked. Cylinder 1 is solid green, and cylinder 2 is green and white, check ground wire while your there.

If fuel is the issue, the primer should be very firm when pumped while not running. You can remove the front hood cover and looking at the carb see the fuel rise to the top of the main jet. Check the fuel lines at all fittings that they are tight and cant be twisted. The fuel pump diaphram is easy to replace and around 5-7 bucks. That wouldn't affect the starting, but could be a reason the motor would die after running a while.

 

[rooster519]

Re: 1984 35 hp mercury outboard won't start

Thanks for the fast reply last night. I went and picked up an inline spark tester and it showed no spark on either cylinder. So it is possible it's not getting spark, or that its a bad tester, lol. I'm going to try to do some further testing but have to wait until I have another set of hands. I traced the wires up to the switch box and noticed that all of the studs, wires and nuts were covered with a nasty grease type coating, most of which was green. It looks almost like a corrosive build up that has gotten wet. Didn't know if that was some type of grease that was put on there to help stop corrosion from happening or if I should remove it, clean all the fittings well and recheck for spark. Any thoughts?

 

[motoman125yztb]

Re: 1984 35 hp mercury outboard won't start

I would say clean it all off. The last thing you want is a current grounding anywhere if its a conductive gel. Another thing to check is the cutoff switch at the remote controls. Make sure its flipped to run. And you can trace the tilt switch on the exhaust cover, looks like a black AA battery. Its a black and yellow wire, You can disconnect that from the switchbox temporarily to check its not throwing a kill signal. And if that still doesnt get a spark you'll need a multimeter. Remove the brown and white, and the brown and yellow wires. Test resistance between them should be 750-1400 ohms. That is the trigger, On a 2 cylinder it controls spark to both and could be the cause. A good tester is the adjustable spark tester its 6 bucks at the auto parts store and can be used to also test spark strength. This motor should jump a 3/8 inch spark.

 

[rooster519]

Re: 1984 35 hp mercury outboard won't start

I will get it all cleaned off. Your thoughts were like mine about it being a conductive gel. I did check the switch at the controls and it is in the run position. I found the tilt switch on the exhaust cover but did not disconnect it. Since it's still a water tight connection, I didn't want to mess with it if I didn't have to. So I tested the resistance on the switchbox and it's only coming in at about 520-550. I"m assuming that, that is the cause of at least my spark problem. I have an old motor from another boat but it's a 150 and a totally different part so I guess I'm going to have to break down and buy a new one. Do you know where I can pick one up quickly and cheaply? LOL. I appreciate all of your help.

 

[rooster519]

Re: 1984 35 hp mercury outboard won't start

Well just a quick update. I called an old friend of mine to come help me try and figure out this motor problem, and apparently I was using the ohm meter incorrectly. He said there was 782 ohms reading at the pegs, he then checked spark with a different inline tester and the spark was bright blue and jumped an easy 3/8 inch. He checked fuel to the carb and there was none. So we proceeded to pull the fuel line between the carb and the fuel pump and we had gas shooting out of that when the bulb was squeezed. We then pulled the carb, and the bowl was full but still no gas making it into the main jet, so the assumption is a clog somewhere in the carb. I will get a rebuild kit ordered for it and probably for the fuel pump as well just to be on the safe side. Thanks again for all your help.