2005 Mercury 8 HP 4 Stroke Issue

[mikes1990]

2005 8HP 4stroke. take the boat out , runs fine for 20 minutes. while on full thottle it just dies out like if the fuel was cut or something. if i try to restart it , it wont. clean the carb , take it out ran good. next time i took it out , the same thing happened. i also noticed at home while flushing the engine immediately gas would pour out from the bottom and it would shut off. so i figured that was my issue , float or something getting stuck. so i installed a new float valve , cleaned the carb well , dumped the old gas , put rec fuel ( premium with no ethanol ) , and added stabilizer. boat was running good , then boom , same thing starts happening. only now , i can crank it back up and it rides fine for a little bit and then it happens again. any ideas? ive been fighting this problem for almost a year now with no solutions. i was going to take it in to my local mechanic but they charge 95 dollars an hour. and who knows how long its going to take them.


also before you tell me to rebuild the carb , there is no carb rebuild kit for this engine. ive looked everywhere.


***update 4/16 I Was Able To Record When It Happens.**

View My Video

 

[MH Hawker]

Re: 2005 Mercury 8 HP 4 Stroke Issue

Heat is causing a component to break down. Do the ohm tests when its down. More than likely its the stator or the trigger. Carbs do not magically cure them selves from sitting.

 

[mikes1990]

Re: 2005 Mercury 8 HP 4 Stroke Issue

Heat is causing a component to break down. Do the ohm tests when its down. More than likely its the stator or the trigger. Carbs do not magically cure them selves from sitting.

thanks for your response hawker. could you explain a little bit about testing the ohms. like what and where do i test and what am i looking for. i have looked on the parts diagram and cant seen to find the stator. this is a 4 stroke model. thanks a bunch

 

[mikes1990]

Re: 2005 Mercury 8 HP 4 Stroke Issue

also , this is the pull start model. not electric.

 

[MH Hawker]

Re: 2005 Mercury 8 HP 4 Stroke Issue

Outboards have a stand alone ing system. It has a basic system of 4 parts. A stator that is under and inside of the fly wheel. This produces the voltage to make ever thing run. The trigger, it is under the flywheel and is conected by a rod to the carb mechanism, it controls the timing and timing advance an the carb is opened. The spark coils. The stator and the trigger connects to the CDI box. the CDI box sends voltage out to the coils in time to firs the plugs. in your case i would think your one of those components is going bad due the he motor heating up, its not common but it dose happen and is hard to find for that very reason and hard to find due to it fails out on the water and not on muffs.

Depending on your exact motor and the components each has a test with a ohm meter and you will have to do it when the motor has failed. you may be able to get the component test info from this link but I got mine from a manual.

http://http://www.cdielectronics.com/support/

 

[mikes1990]

Re: 2005 Mercury 8 HP 4 Stroke Issue

edit.

 

[mikes1990]

Re: 2005 Mercury 8 HP 4 Stroke Issue

Outboards have a stand alone ing system. It has a basic system of 4 parts. A stator that is under and inside of the fly wheel. This produces the voltage to make ever thing run. The trigger, it is under the flywheel and is conected by a rod to the carb mechanism, it controls the timing and timing advance an the carb is opened. The spark coils. The stator and the trigger connects to the CDI box. the CDI box sends voltage out to the coils in time to firs the plugs. in your case i would think your one of those components is going bad due the he motor heating up, its not common but it dose happen and is hard to find for that very reason and hard to find due to it fails out on the water and not on muffs.

Depending on your exact motor and the components each has a test with a ohm meter and you will have to do it when the motor has failed. you may be able to get the component test info from this link but I got mine from a manual.

http://http://www.cdielectronics.com/support/

if you dont mind , could you tell me which one is the trigger?


http://imageshack.com/a/img203/1859/nbt5.png

 

[ondarvr]

Re: 2005 Mercury 8 HP 4 Stroke Issue

Run it until dies and then immediately check to see if it has spark at the plugs, this will at least narrow it down, if there's no spark then you can start checking each electrical component .

 

[mikes1990]

Re: 2005 Mercury 8 HP 4 Stroke Issue

the problem is , after it dies i can start it back up most of the times. and it only happens out in the water. so it would be kind of difficult to check the spark out on the water.

 

[ondarvr]

Re: 2005 Mercury 8 HP 4 Stroke Issue

If it starts right back up it's normally not electrical, but checking for spark is done on the water all the time. I've done it on my 200HP v6 to verify which coils were failing at full throttle.

Floats can stick open, closed, or in between, the float level can cause it to die also. along with a bad fitting connection (O-rings in the fitting), plus other things. Fuel flowing out indicates it's still float related.

If stops running like a switch was flipped it's normally electrical, if slows down and fades away it's normally fuel related.

 

[mikes1990]

Re: 2005 Mercury 8 HP 4 Stroke Issue

If it starts right back up it's normally not electrical, but checking for spark is done on the water all the time. I've done it on my 200HP v6 to verify which coils were failing at full throttle.

Floats can stick open, closed, or in between, the float level can cause it to die also. along with a bad fitting connection (O-rings in the fitting), plus other things. Fuel flowing out indicates it's still float related.

If stops running like a switch was flipped it's normally electrical, if slows down and fades away it's normally fuel related.

it doesnt fade away. it shuts off completely. it feels almost exactly like when you hit the kill switch on the tiller handle. once it shuts off , a few tries later it starts up and runs , but then shortly after does it again. before i switched the gas and replaced the float valve it would not turn back on until i took apart the carb and cleaned it. what would be the easiest way to check the spark out on the water?

 

[ondarvr]

Re: 2005 Mercury 8 HP 4 Stroke Issue

I'm glad you mentioned the kill switch, they frequently short out right were it flexes at the hinge point. Disconnect the wires and see if it helps.

Also to check the spark, right when the motors dies pull the cowl off and either pull out one plug or carry an extra one with you. Connect the plug to the plug wire and ground it against the block and pull the rope. It should have a nice bright spark, if not that could be the problem.


It can still just shut off if it's fuel related, but you need to identify which it is before any actual fixing can be done.

 

[mikes1990]

Re: 2005 Mercury 8 HP 4 Stroke Issue

I'm glad you mentioned the kill switch, they frequently short out right were it flexes at the hinge point. Disconnect the wires and see if it helps.

Also to check the spark, right when the motors dies pull the cowl off and either pull out one plug or carry an extra one with you. Connect the plug to the plug wire and ground it against the block and pull the rope. It should have a nice bright spark, if not that could be the problem.


It can still just shut off if it's fuel related, but you need to identify which it is before any actual fixing can be done.

lets say it was fuel related , i mean what other thing could it possibly be ? i mean , the vent on the tank works , new hose with prime ball , good fuel with stabilizer and new float valve. ? by the way , thanks for all the help , it means alot. trying to get this dam thing running right before summer.

 

[ondarvr]

Re: 2005 Mercury 8 HP 4 Stroke Issue

If fuel pours out when the issue takes place, then it's still float related. It could be gunk in the line finding it's way to the float valve, or the float still sticking on it's own. That's about all it can be. These small 4 strokes are very finicky when it comes to having a clean carb.

 

[mikes1990]

Re: 2005 Mercury 8 HP 4 Stroke Issue

If fuel pours out when the issue takes place, then it's still float related. It could be gunk in the line finding it's way to the float valve, or the float still sticking on it's own. That's about all it can be. These small 4 strokes are very finicky when it comes to having a clean carb.

Well i havent had the fuel pouring out issue anymore. as far as the line. which line are you talking about ? because the line from the tank to motor is brand new and is ethanol compliant .

 

[mikes1990]

Re: 2005 Mercury 8 HP 4 Stroke Issue

anyone else have any suggestions?

 

[racerone]

Re: 2005 Mercury 8 HP 4 Stroke Issue

Oil pressure switch ??

 

[mikes1990]

Re: 2005 Mercury 8 HP 4 Stroke Issue

Oil pressure switch ??

i dont think so , the oil pressure light does not come on while running. only during the initial startup , which is normal.

 

[MH Hawker]

Re: 2005 Mercury 8 HP 4 Stroke Issue

Perhaps a wire has the insulation rubbed and grounding.

 

[ondarvr]

Re: 2005 Mercury 8 HP 4 Stroke Issue

Did you check the kill switch wires?