nicklanigan
Contributing Member
Hi all,
Here's a bit of a post about some symptoms experienced with my outboard, how they were resolved, and a bit about how things work.
I've spent the last two seasons with pretty erratic behaviour from my motor, and whilst it never let me down completely, I have had to limp home a couple of times, and even worse, have had to cancel a couple of outings for the kids.
You can probably find what appears below anywhere on the web, but the info tends to be widely spread out, and difficult to gain a simple, concise overview. I am an electrical engineer by training.
My experiences have been with a 39 year old motor (she's 40 next year). I've owned it around 8 years, and done very little to it in that time - it just worked. Not so the last two seasons, where I've suffered from the following from time to time. The numbering is important, as I'll describe the problem and fix for each one.
1. Hard starting (and even impossible starting on the boat ramp)
2. Hard restarting
3. Complete nothing turning the ignition key
4. A click only when turning the ignition key
5. Loss of power after about 20 minutes running
6. Stall after a restart when trying to go above about 2000rpm
7. Complete loss of spark to one cylinder
8. Battery not charging
9. Tach intermittingly not working
You'll often hear that you need 3 things to make an outboard run - compression, fuel and a spark. Don’t assume anything about what might be causing a problem – best to check everything out.
Ok, dealing with each in turn, and I’d explore things in this order…
Compression
If you've got a problem, test the compression first. A compression problem indicates something is really wrong, and needs to be sorted before worrying about anything else. At minimum you're up for head gasket replacement. So, if you have uneven or low compression, sort that first. Low compression all round might not be that bad - but uneven definitely signals a problem.
You need a plug wrench and compression gauge to carry this out.
Fuel
If everything is going well – the fuel system works as follows:
The fuel primer bulb is squeezed a few times, fuel is pulled from the tank, through the filter/water separator, through the bulb, into the fuel pump, and is actually pushing right into the carb bowls underneath the carburettors. When the bowls are full, valves inside each bowl are closed by floats, and the fuel path is effectively closed. At this time, the primer bulb becomes hard, given there is now nowhere for the fuel to go.
The engine is then cranked over by the starter, normally with the warm up lever raised to advance the timing. The spinning motor now has a compression/vacuum cycle, mixing fuel with air drawn into the crankcase via specific routes within the carb, is compressed, and a spark provided at just the right time.
As the motor spins, the compression/vacuum cycles also power the fuel pump located on the side of the engine – fuel is now pumped by the fuel pump – as the level in each carb bowl lowers, the float allows the valve to open, allowing the carb bowl to refill.
Any leak or blockage in the fuel system will not allow all this to happen.
Assuming you've sorted the basics (fresh fuel, mixed if needed, air valve clear, filter clean etc), check out all the hose, from tank to the carburettor intakes. To do this, you may need to remove the carbs, but we’ll get to them shortly.
In a motor this old, if you don’t know when the fuel line was last replaced, I’d replace the lot now, including the fuel bulb, and any fittings along the way that look worn. In my case, about half the line had cracks – the pre-bent pieces feeding the carbs from the fuel pump were badly cracked on in the inside of the curves – damage not visibly until the carbs were removed.
In addition, I found that by squeezing the fuel bulb, fuel would leak out of the fuel pump – clearly not good, so a new fuel pump was needed.
You’ll find that a “carb rebuild” gets mentioned as the solution for pretty much any problem on boat repair forums. Hmm… I’m not so sure.
However, if you have no idea when someone last took a look at the carbs, it’s probably a good idea to do so. At least that way, you’ll know that they are in good shape once done, and are unlikely to cause you problems.
One of my carbs was perfect, whilst the other contained rusty water – a sure sign of water in the fuel. However, sorting this didn’t actually solve anything for me – but at least I know the carbs are clean and in good order now I’ve rebuilt them.
The rusty muck in the carb alerted me to the need for a filter/water separator, so I installed one in the fuel line.
None of this work directly fixed any of my issues listed above – although I suspect it helped with starting and restarting issues – bad fuel line/primer bulb may allow fuel to empty out of the fuel line back to the tank, making it harder work to restart next time unless the primer bulb is re-used as the fuel pump has to pump air for a bit which is really hard work for it.
However, I now know that fuel is being filtered, that any water in the fuel should be removed before making to the carbs again, and that all the fuel line is good, as is the primer bulb. I also know the carbs are clean internally.
The other area to check is the fuel intake within the tank itself – in my case it is just too difficult to get to, and I’m not experiencing a collapsing primer bulb that would be the key sign of a blockage on the intake in the tank.
You may or may not have found a smoking gun so far – if so, great, but I’d keep going anyway in case more is wrong. I though the rusty water in a carb bowl was the source of my grief – unfortunately not.
OK, so that’s fuel taken care of.
The Spark (well, actually, the entire electrical system)
Ok, so up to now, things have been pretty easy. Electrics on the other hand are a bit trickier. It’s often said that the electrical system on an outboard is the most likely area to fail – I’d have to agree. The heat and vibrations are just a nightmare environment for electrical components and wiring.
So what do we have with all those wires?
It’s easiest to consider them as different systems, which are they. I describe them as follows. These three are almost completely independent of each other.
Starting System
The starting system is what we use to start the outboard. Your battery is connected by two large wires (a positive and a negative one) to the starter solenoid (the positive wire) and just the engine metal (the negative wire).
This system is predominately DC.
When the start key is turned, a small current has to flow through the neutral switch, located in the remote control unit, to the starter solenoid. The small current makes a mechanical plunger inside the starter solenoid move, connecting the 12v from the battery, through the starter solenoid, to the starter motor. This system uses the motor metal as a return path, hence the heavy cable from the battery being connected to a metal stud on the motor.
The starter motor must be able to spin the engine fast enough for the Spark System to work (which is covered below). To achieve this, you must be able to deliver about 9.5v across the starter motor. Doesn’t sound too hard given the voltage of your starter battery, but the currents involved are huge, and therefore the losses from any resistance are large also.
So what can go wrong here?
Bad connections to batteries, to the motor, or any added connectors such as an isolator switch, can all add unneeded voltage drop. In my case, I found very loose battery connectors, and a large loss occurring through an isolator switch. I had to remove the isolator switch, and re-crimp the battery connection.
This sorted my problem of difficult starting.
My next problem was that occasionally, I’d turn the start key and get either a click from the engine, or nothing at all.
Taking these in turn – the click you hear is the starter solenoid plunger moving. So, if you get a click, but nothing else, either the starter motor is bad, or the starter solenoid is bad. In my case, the starter solenoid was full of a black dust, preventing electrical contact from being made. The plunger would still move ok, and give a nice click, it just wouldn’t conduct anything. These aren’t repairable, so will need to be replaced if failed. A volt meter will easily point you in the right direction.
If nothing happens when you turn the start key, you could have a failed neutral start switch. Mine slowly failed over time, so ultimately I just removed it from the circuit. It’s located in the remote console.
Here's a bit of a post about some symptoms experienced with my outboard, how they were resolved, and a bit about how things work.
I've spent the last two seasons with pretty erratic behaviour from my motor, and whilst it never let me down completely, I have had to limp home a couple of times, and even worse, have had to cancel a couple of outings for the kids.
You can probably find what appears below anywhere on the web, but the info tends to be widely spread out, and difficult to gain a simple, concise overview. I am an electrical engineer by training.
My experiences have been with a 39 year old motor (she's 40 next year). I've owned it around 8 years, and done very little to it in that time - it just worked. Not so the last two seasons, where I've suffered from the following from time to time. The numbering is important, as I'll describe the problem and fix for each one.
1. Hard starting (and even impossible starting on the boat ramp)
2. Hard restarting
3. Complete nothing turning the ignition key
4. A click only when turning the ignition key
5. Loss of power after about 20 minutes running
6. Stall after a restart when trying to go above about 2000rpm
7. Complete loss of spark to one cylinder
8. Battery not charging
9. Tach intermittingly not working
You'll often hear that you need 3 things to make an outboard run - compression, fuel and a spark. Don’t assume anything about what might be causing a problem – best to check everything out.
Ok, dealing with each in turn, and I’d explore things in this order…
Compression
If you've got a problem, test the compression first. A compression problem indicates something is really wrong, and needs to be sorted before worrying about anything else. At minimum you're up for head gasket replacement. So, if you have uneven or low compression, sort that first. Low compression all round might not be that bad - but uneven definitely signals a problem.
You need a plug wrench and compression gauge to carry this out.
Fuel
If everything is going well – the fuel system works as follows:
The fuel primer bulb is squeezed a few times, fuel is pulled from the tank, through the filter/water separator, through the bulb, into the fuel pump, and is actually pushing right into the carb bowls underneath the carburettors. When the bowls are full, valves inside each bowl are closed by floats, and the fuel path is effectively closed. At this time, the primer bulb becomes hard, given there is now nowhere for the fuel to go.
The engine is then cranked over by the starter, normally with the warm up lever raised to advance the timing. The spinning motor now has a compression/vacuum cycle, mixing fuel with air drawn into the crankcase via specific routes within the carb, is compressed, and a spark provided at just the right time.
As the motor spins, the compression/vacuum cycles also power the fuel pump located on the side of the engine – fuel is now pumped by the fuel pump – as the level in each carb bowl lowers, the float allows the valve to open, allowing the carb bowl to refill.
Any leak or blockage in the fuel system will not allow all this to happen.
Assuming you've sorted the basics (fresh fuel, mixed if needed, air valve clear, filter clean etc), check out all the hose, from tank to the carburettor intakes. To do this, you may need to remove the carbs, but we’ll get to them shortly.
In a motor this old, if you don’t know when the fuel line was last replaced, I’d replace the lot now, including the fuel bulb, and any fittings along the way that look worn. In my case, about half the line had cracks – the pre-bent pieces feeding the carbs from the fuel pump were badly cracked on in the inside of the curves – damage not visibly until the carbs were removed.
In addition, I found that by squeezing the fuel bulb, fuel would leak out of the fuel pump – clearly not good, so a new fuel pump was needed.
You’ll find that a “carb rebuild” gets mentioned as the solution for pretty much any problem on boat repair forums. Hmm… I’m not so sure.
However, if you have no idea when someone last took a look at the carbs, it’s probably a good idea to do so. At least that way, you’ll know that they are in good shape once done, and are unlikely to cause you problems.
One of my carbs was perfect, whilst the other contained rusty water – a sure sign of water in the fuel. However, sorting this didn’t actually solve anything for me – but at least I know the carbs are clean and in good order now I’ve rebuilt them.
The rusty muck in the carb alerted me to the need for a filter/water separator, so I installed one in the fuel line.
None of this work directly fixed any of my issues listed above – although I suspect it helped with starting and restarting issues – bad fuel line/primer bulb may allow fuel to empty out of the fuel line back to the tank, making it harder work to restart next time unless the primer bulb is re-used as the fuel pump has to pump air for a bit which is really hard work for it.
However, I now know that fuel is being filtered, that any water in the fuel should be removed before making to the carbs again, and that all the fuel line is good, as is the primer bulb. I also know the carbs are clean internally.
The other area to check is the fuel intake within the tank itself – in my case it is just too difficult to get to, and I’m not experiencing a collapsing primer bulb that would be the key sign of a blockage on the intake in the tank.
You may or may not have found a smoking gun so far – if so, great, but I’d keep going anyway in case more is wrong. I though the rusty water in a carb bowl was the source of my grief – unfortunately not.
OK, so that’s fuel taken care of.
The Spark (well, actually, the entire electrical system)
Ok, so up to now, things have been pretty easy. Electrics on the other hand are a bit trickier. It’s often said that the electrical system on an outboard is the most likely area to fail – I’d have to agree. The heat and vibrations are just a nightmare environment for electrical components and wiring.
So what do we have with all those wires?
It’s easiest to consider them as different systems, which are they. I describe them as follows. These three are almost completely independent of each other.
Starting System
The starting system is what we use to start the outboard. Your battery is connected by two large wires (a positive and a negative one) to the starter solenoid (the positive wire) and just the engine metal (the negative wire).
This system is predominately DC.
When the start key is turned, a small current has to flow through the neutral switch, located in the remote control unit, to the starter solenoid. The small current makes a mechanical plunger inside the starter solenoid move, connecting the 12v from the battery, through the starter solenoid, to the starter motor. This system uses the motor metal as a return path, hence the heavy cable from the battery being connected to a metal stud on the motor.
The starter motor must be able to spin the engine fast enough for the Spark System to work (which is covered below). To achieve this, you must be able to deliver about 9.5v across the starter motor. Doesn’t sound too hard given the voltage of your starter battery, but the currents involved are huge, and therefore the losses from any resistance are large also.
So what can go wrong here?
Bad connections to batteries, to the motor, or any added connectors such as an isolator switch, can all add unneeded voltage drop. In my case, I found very loose battery connectors, and a large loss occurring through an isolator switch. I had to remove the isolator switch, and re-crimp the battery connection.
This sorted my problem of difficult starting.
My next problem was that occasionally, I’d turn the start key and get either a click from the engine, or nothing at all.
Taking these in turn – the click you hear is the starter solenoid plunger moving. So, if you get a click, but nothing else, either the starter motor is bad, or the starter solenoid is bad. In my case, the starter solenoid was full of a black dust, preventing electrical contact from being made. The plunger would still move ok, and give a nice click, it just wouldn’t conduct anything. These aren’t repairable, so will need to be replaced if failed. A volt meter will easily point you in the right direction.
If nothing happens when you turn the start key, you could have a failed neutral start switch. Mine slowly failed over time, so ultimately I just removed it from the circuit. It’s located in the remote console.