'94 Mercury 25hp 2-stroke won't start, it did last week...

[Dustin Taylor]

Quick history: I have a 94 Bass Tracker with a Mercury 25hp 2 stroke. She has always been a reliable engine. Several years back I had issues starting the engine from the ignition when cold. Sometimes it would work and sometimes I would have to use the pull starter. After running it initially, it would start via the ignition without issue throughout the trip. As time went on however, it would be hit or miss as to the ignition firing after doing that first pull start. Then, as you can guess, the ignition failed to work all together. It has been like this for a few seasons now and pull starting it was never difficult. I of course would turn the ignition key, choke and she would fire up in a few pulls cold or a single when warm.

Fast forward to this season. After my initial check for it's first run I found that the inline fuse going to the starter battery from the console had corroded and broken off. No big deal, we were just doing a quick run around the lake. Before we put it in I added new spark plugs, hooked it up to the hose, turned the key, pulled a few times and it started. Put it in the lake and went the whole trip without issue, starting and stopping the motor several times and always checking the impeller was running water. I brought it back and replaced the inline fuse and put in a 20amp. I tried a 10amp first because I didn't know what I should use and it was corroded beyond recognition. With the 10amp I couldn't even hear the bilge but the 20amp seemed to be fine. Double checked that all the wiring was properly connected back to the starter and trolling battery.

Went out the following weekend, added 6 gallons of fresh fuel and oil, dropped it in the water, pulled the started till my arm fell off and could not get it to fire. Checked landyard switch and it wasn't the issue. I don't think it is the inline fuse I replaced as it worked when it was completely severed. What could prevent it from being pull started when it was perfectly fine the week before? The ignition I understand, and if anyone could give insight into that it would be appreciated but I have not using it for years anyway (I can faintly hear it trying to crank when I turn the ignition).

Any help is appreciated. Thanks!

Oh, my own personal diagnosis was my fishing buddy bragging to the other guy at the ramp that day about how we have never had an issue with the engine in over 15 years. I still blame his mouth.

 

[DaleH]

I've never seen corrosion built up at all in on-line OB fuse. How did the water get in there, was this a submerged OB you bought without knowing it? I have seen faulty ignition switches cause all sorts of starting problems.

With that much corrosion, resistance check your OB cables. If OK & battery is OK and starter still turns that faint (little), then it might be a candidate for a rebuild. But I'd do some voltage checking first, i.e., battery voltage vs same when cranking etc. Some Motor ECMs or ECUs won't fire if the motor see < 10 VDC whilst cranking.

 

[weimed]

take starter fluid and spray into the carb. if it starts right up then you either have a dirty carb or fuel delivery issue. Do that then report back.

 

[crazymanme2]

[quotetake starter fluid and spray into the carb. if it starts right up then you either have a dirty carb or fuel delivery issue. Do that then report back.][/quote]

Worst thing for a 2 stroke [-X

 

[JMichael]

take starter fluid and spray into the carb. if it starts right up then you either have a dirty carb or fuel delivery issue. Do that then report back.

2 stroke engines don't have oil in the crankcase. The engine is lubricated by the oil contained in the fuel. Starting fluid/ether not only doesn't contain any oil or lubricant, it does an excellent job of washing away any oil that might have been there. While starting fluid is a wonderful thing to use on cold or hard starting 4 cycle engines, it's a nightmare for a 2 stroke engine. It doesn't take long for bearings and other metal on metal parts to self destruct when you operate them without lubrication.

 

[Dustin Taylor]

Thanks for the replies guys.
I picked up a new bulb and line and a small one gallon tank that I can mix some oil in and try that.
I just need to find some time to try it Probably this weekend.
To calrify the corroded inline fuse was not in the OB but the one coming from the console to the starter battery. (It did get wet)...

 

[CMOS]

Just a quick tip: I suggest learning to use a soldering iron to solder the connections, even if they are crimped to a ring or spade lug. It's easy to learn, and cheap. Once soldered you will not have to worry about that connection ever again.

CMOS

 

[Dustin Taylor]

Cleaned out the fuel filter and connected the new bulb and line to a fresh gallon with oil mixed, no results.

Quick question: If I blow into the fuel line directly connected to the carb should it be blocked or should air pass into it? (because I could not blow air directly into the carb and not sure if it is blocked?).

 

[JMichael]

It's going to depend on whether there is fuel in the float bowl or not. If the bowl is full, then the float valve should be shut and should not allow you to blow air into it. If the bowl is empty or low, air should flow in.

 

[onthewater102]

Did your 10 amp fuse blow out? If not there was no need to replace it with a 20 amp. If you are having issue getting power to your bilge through that connection it is likely that there is another break in the wiring somewhere down the line. Too often guys use automotive splice connectors in marine applications and they just corrode away to nothing. Try a continuity tester to see if you have resistance in the wire between the fuse holder and the other devices (bilge, lights etc.)

The issue you've described (where you could pull start it ok but it wouldn't start on its own) is with your starter, not the ignition. The ignition system feeds power to the spark plugs, the starter engages the flywheel to turn the motor electrically until the gas engine fires up and takes over. Starters are fairly inexpensive, and are usually very easy to change, two or three bolts and a couple of screwed in electrical connections.



As far as your motor not firing, seeing as you've had corrosion issues with your electrical system already that would be the first culprit I'd try to eliminate as your non-running cause. If you don't fix your starter first you'll need someone to help you, but what you want to do is pull the spark plugs out, then put a screwdriver in one plugwire to make contact with the connector and hold it very close (1/8 inch away or less) to the block as you have someone pull the starter cord. you should see blue spark jumping from the screwdriver to the block. Check both wires and inspect the plugs to make sure they're not corroded up. You can repeat the test with the plug in the wire by holding the wire jacket and touching the threaded side of the plug to the block and having someone pull the cord and inspecting the plug for spark, it might be less noticeable than the arc from the screwdriver though.

 

[Dustin Taylor]

The inline fuse was too corroded to see what it was originally, but the 20amp works good. I replaced it with a waterproof marine grade inline fuse.
All of the inline fuses in the motor have been checked and look good.
I also checked that both plugs spark as well. They are new and have less than an hour drive time on them.

I have to drain the carburetor and then see if there is any blockage.

 

[onthewater102]

Did the 10 amp blow though? If you system will run on a 10 amp fuse without blowing it then you shouldn't have a 20 amp. If it did not work with the 10 amp but didn't burn out the 10 amp and then worked with the 20 then you have a loose connection somewhere because changing the fuse size shouldn't matter.

 

[JMichael]

I have to drain the carburetor and then see if there is any blockage.

Does that motor have the fuel pump made onto the side of the carb? If it does, you may not be able to blow any air through the fuel line if it has to go through the pump as well.

 

[Dustin Taylor]

Did the 10 amp blow though? If you system will run on a 10 amp fuse without blowing it then you shouldn't have a 20 amp.

The 10amp wouldn't power the bilge at all really and the light on the bilge switch would barely light up. The 20amp made it run normally.

It dawned on me shortly after that the fuses in the panel under the console should be the same or under and they were all 20amp.

Electrical is not my strong suit...

 

[Dustin Taylor]

Does that motor have the fuel pump made onto the side of the carb? If it does, you may not be able to blow any air through the fuel line if it has to go through the pump as well.

I don't think so. Just the bulb and line going to the fuel filter, then a line to the carb.

 

[JMichael]

There has to be a fuel pump in there somewhere. If you don't see anything between the filter and the carb, my bet is that it's made onto the side of the carb.

 

[onthewater102]

The 10amp wouldn't power the bilge at all really and the light on the bilge switch would barely light up. The 20amp made it run normally. It dawned on me shortly after that the fuses in the panel under the console should be the same or under and they were all 20amp. Electrical is not my strong suit...

That doesn't make any sense. If the 10amp fuse was insufficient for the load it would have burned out - switching to a 20amp makes no difference. If it did it's because you've got wiring issues between the fuse an the devices and you must have jostled the wires in the process of replacing the fuse or something.

There has to be a fuel pump in there somewhere. If you don't see anything between the filter and the carb, my bet is that it's made onto the side of the carb.

I just ordered your carb for my motor. As you're looking at your pump there is a clearish/yellowish plastic panel left of the intake as you're looking at it mounted on the motor. That area houses your fuel pump. Look up your motor on Boats.net using the serial # on the bracket mounting the motor to the transom. In the carb diagram you will see part #11 is the fuel pump body. The diaphragms alongside it on the left in the diagram is the part they're directing you to.