Logo
FULL SITE MENU

8hp mercury 2-stroke outboard speed problems

1

14mclark

Member
i have a 1980's Mercury 2-stroke 8hp outboard. When i run it, i start it with the choke. Once it can run without it, i push it in. The problem is i run it at full throttle and it only goes half speed. Sometimes it kicks itself into full speed. It usually takes a long time for it to do this though. Suggestions?
 
... it only goes half speed. Sometimes it kicks itself into full speed.
Click to expand...
The engine sounds like it is only running on one cylinder most of the time. Put a timing light on each wire to see which one is not firing. There may be a failing coil or coil wire. Check them for resistance, corrosion or loose connection.
 
Mine used to do this. After changing plugs, both coils, fuels lines and filter and after a service by a Merc dealer who was aware of the fault, it turned out to be dirt and water droplets in the carb bowl (ever so small but there nonetheless). And get this, cleaning the carb is not a part of routine service. Now she screams and just wants to go and go.
 
There is no " easy way "----- it must be taken apart / inspected and cleaned.-------------Usually no parts required.----------------Carburetor cleaning spray just does not work , you must take the carburetor apart.------------Always run fuel out of the carburetor when storing the motor.
 
8hp mercury 2-stroke, 2-cylinder outboard motor: I put two new spark plugs in for each of the two cyclinders, grounded the bottom cylinder first, then the top. When i grounded the bottom spark plug, there was no spark, and when i grounded the top one, it sparked. Then to further test my situation, i switched the spark plugs, the same thing happened, the bottom spark plug didn't spark. My only conclusion is that the wires are bad because i know that the spark plug is good. How do i fix this problem? Suggestions?
 
Wires or the coil and CD box is bad ??????------------You should be able to switch wires from one coil to the other for your testing.
 
i switched the wires and tested them, the same thing happened the bottom spark plug diddn't spark, so am i left to assumes that it is in the coil or the cd box? suggestions?
 
I disconnected most of the wires, including the ground, and i hooked them back up, when i did that i grounded my bottom plug and got a spark 2 or 3 times, but then i tried it again 10 mins. later and grounded my plug and didn't get a spark, is my probolem in the coil?
 
I switched the coils and tested them, same thing, the top spark plug sparked and the bottom one didn't when i grounded them. now, i have basically determined that the spark plug wires (wires from the coil to the spark plugs) and the coils are good and working. I assume that the problem is in the wires from the coil to the fly wheel and all of those wires? Suggestions?
 
there wasn't any corrosion on the wires, looked pretty clean, what is the box and what does it do? should i replace it? if so, where do i get one?
 
depends on your level of expertise I would say.--------------Nothing but a collection of 49 cent bits in there so to speak.------Tough to get at them without doing more damage.
 
If you have not been trained in troubleshooting electronic circuitry or in soldering electronic components then buy a new one since you will be waisting you time and money.
 
today i wired the bottom spark pug through the wire and up to the top spark plug's coil, (the bottom and the top spark plug were wire on the top coil), the bottom spark plug's coil isn't in use, there is not wire in it, i tested both spark plugs, and they sparked, is there anything wrong with me doing this?
 
http://www.outboardignition.com/support/114-7452K1.pdf

This is the 2nd. time I have posted the directions for you. You need to follow the simple trouble shooting directions in the lower half to determine if the switchbox needs to be replaced. #339-7452A1 Fits: 8 HP Mercury\Mariner 1986-96 models with serial #A197112-G289100. Buy it here--I checked aroung this site has the lowest price.
 
I am pretty sure that the problem is the switchbox, but before i buy a new switchbox (my number is #339-7452 A10), i wanted to make sure that the switchbo is the problem and it isn't something else like the stator or something?
 
Back
Top