1986 Mercury 20 HP 2 Stroke

[3rd Generation Lund]

My engine is not starting. I have changed the plugs, they cylinders are getting fuel and flushed lower unit oil. I am now changing the fuel filter, hoping it will help. My last resort is that the run/stop switch is not operating properly. Any thoughts on this? How do I bypass the switch to identify if it is the problem. Any guidance would be helpful.

Thanks!

 

[sutor623]

Re: 1986 Mercury 20 HP 2 Stroke

My engine is not starting. I have changed the plugs, they cylinders are getting fuel and flushed lower unit oil. I am now changing the fuel filter, hoping it will help. My last resort is that the run/stop switch is not operating properly. Any thoughts on this? How do I bypass the switch to identify if it is the problem. Any guidance would be helpful.

Thanks!

If you pull the red switch cap off, and then check the two wires for a short.

 

[sutor623]

Re: 1986 Mercury 20 HP 2 Stroke

And I wouldnt say last resort. Check the plugs for spark by grounding on block. If you are getting spark then it is not the switch. Pour fuel into the carb just to be sure. Check all gas lines for leaks.

 

[gwukena]

Re: 1986 Mercury 20 HP 2 Stroke

By the way good spark may not mean squat if aint't in time. Flywheel has a key, if you have good spark, check for a sheared key.

 

[BigJeff]

Re: 1986 Mercury 20 HP 2 Stroke

I was helping with this motor and there seems to be good spark but it doesn?t seem to want to go. We tried putting a little gas in the cylinder and it didn't seem to even pop off. All other two strokes I have used have always ran a little when you put gas into the cylinders.

Where should he look for the fly wheel key? And would it move the cylinders if the key was sheered?

Also I am not positive the cylinders are getting fuel, there is a brand new fuel line and it will not get hard.
Besides plugged up fuel filter what else needs to be cleaned up if the gas went bad over the winter. I am wondering if it?s not something in the carb, may be a plugged needle?

But that was all over the weekend not sure where 3rd Generation Lund got since then.

 

[3rd Generation Lund]

Re: 1986 Mercury 20 HP 2 Stroke

Quick update -

The spark is good, the kill switch is operating properly and I just changed the fuel filter. It now sounds like it wants to go but won't fire. When I pull the starter cord there is smoke coming out at the prop. What would be the cause of this?

 

[sutor623]

Re: 1986 Mercury 20 HP 2 Stroke

Fuel pump and/or carb are dirty. Pour a bit of gas into the carb or spark plug hole. If it fires up, you know what you need to do.

 

[3rd Generation Lund]

Re: 1986 Mercury 20 HP 2 Stroke

I just rebuilt the carb with fresh gaskets and fittings. On first pull it sounded like it wanted to fire, then not so much. Adjusted plugs, tried everything I know how to do. When I pull the starter cord with the plugs off, the bottom cylinder shoots fuel out, but the top not nearly as much. I sprayed seafoam in the cylinders to try and clear the top one out. Any other thoughts on why this thing isn't firing yet?

 

[3rd Generation Lund]

Re: 1986 Mercury 20 HP 2 Stroke

After speaking with a local small engine shop, the gentleman told me that the spark plugs I bought were the wrong model (Champion QL78YC). He told me to buy a surface gap plug, specifically the NGK BUHW. I am now waiting for the plugs to be delivered to my local parts shop and will put them in tonight. Hoping this will help the engine fire properly.

 

[3rd Generation Lund]

Re: 1986 Mercury 20 HP 2 Stroke

If it doesn't fire, would you suspect bad spark plugs? I am suspicious that I bought the wrong model somehow.

 

[sutor623]

Re: 1986 Mercury 20 HP 2 Stroke

If it doesn't fire, would you suspect bad spark plugs? I am suspicious that I bought the wrong model somehow.

While having the correct plug will make the engine run optimally, as well as provide the right clearance (so that the piston doesnt make contact) I highly doubt this is your issue. If the plugs are the culprit you would more than likely have a running engine with the new plugs, just maybe not as smoothly. I point my finger elsewhere.

 

[sutor623]

Re: 1986 Mercury 20 HP 2 Stroke

Also I am not positive the cylinders are getting fuel, there is a brand new fuel line and it will not get hard.
Besides plugged up fuel filter what else needs to be cleaned up if the gas went bad over the winter.

I just rebuilt the carb with fresh gaskets and fittings.

What about fuel pump? You say that the filter has ben changed but if the bulb wont get stay hard you either have a bad fitting on the outboard end of the fuel line, or a bad fuel pump diaphragm.

 

[3rd Generation Lund]

Re: 1986 Mercury 20 HP 2 Stroke

I replaced the fuel pump diaphragm when putting a new carb kit along with all other gaskets inside the carb. If we poured gas into the cylinders and it didn't fire, what would that tell you? I will let you know if the new plugs helped shortly.

 

[sutor623]

Re: 1986 Mercury 20 HP 2 Stroke

I replaced the fuel pump diaphragm when putting a new carb kit along with all other gaskets inside the carb. If we poured gas into the cylinders and it didn't fire, what would that tell you? I will let you know if the new plugs helped shortly.

Yeah in that case it HAS to be electrical. How does the flywheel key look? Is it sheared? Have you checked compression on this motor? If your compression is too low then the motor may not turn over. It is a good thing to rule out. Another thing that people often overlook when this cannot be fixed by carb/ignition check is gasket issues. I had a 4hp that had great compression, but ran like crap. It had a bad exhaust cover gasket, which can not be found by compression test(at least on this motor). Just some things to look at.

 

[3rd Generation Lund]

Re: 1986 Mercury 20 HP 2 Stroke

I am now going to test the compression, spark and try to change the flywheel key in hopes to get the engine to fire. If this doesn't work, I am going to try and replace the kill button on the end of the steering handle as it may be causing the engine to kill. It does not have a key, but is just a button on the end of the steering handle.

 

[3rd Generation Lund]

Re: 1986 Mercury 20 HP 2 Stroke

Compression test showed no issues, the reading was at about 90 for each cylinder. Spark plug test shows good spark. I am now going to order a new flywheel key and hope it solves the problem.

 

[sutor623]

Re: 1986 Mercury 20 HP 2 Stroke

Well glad to hear compression is doing okay. How does the flywheel key look?

 

[sutor623]

Re: 1986 Mercury 20 HP 2 Stroke

There are a lot of ignition parts that could be failing here. Even if it LOOKS like it is sparking okay, I am still wondering...... There is a trigger, ignition coil, stator and switchbox that could be acting up. I would suggest giving this a try if the key doesnt solve the issue. http://www.cdielectronics.com/downloads/troubleshooting%20guide/

 

[3rd Generation Lund]

Re: 1986 Mercury 20 HP 2 Stroke

Quick update here. We got the flywheel off and found a broken trigger assembly. I got the part for 50 bucks and it fired right up. I need to get it timed correctly but a BIG thanks to Sutor and BigJeff for the help! Still have a few weeks before opener to get it timed right!

 

[sutor623]

Re: 1986 Mercury 20 HP 2 Stroke

Cool man, glad I could help.