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2003 4 HP four stroke... weak spark?

S

sobie2

Member
My 4 hp will not run or start. It is a kicker motor on my boat that is never really used. It usually requires the carb to be drained. It did get dunked once a long time ago but even today there is no sign of corrosion on the motor (or the connections).

This year I cannot get the motor to run. I have removed and properly cleaned the carb (it wasn't bad either) and it still will not run. The motor does have spark but I cannot tell if it is weak. It is getting fuel, I replaced the fuel cock which had gunk on the internal screen, and the fuel pump pumps fuel. I used to be able to get the motor to run with some starting fluid but not this year. When I remove the spark plug and ground it and pull on the starter I do get a little spark.

The only reason I am questioning the spark is that I had an early 1990s Mariner 8 hp two stroke this year that sparked but wouldn't run, and the local shop replaced the stator and it now runs great (but a friend paid for this service to the tune of $500).

I can buy a new Lehr propane outboard for $1,000 and rid myself of this engine, but would prefer to investigate it myself. The local shop charges $110/hr. I can easily see a $500 fix bill on this one and would prefer to not through good money at bad.

I know the kill switch is good to because there is a spark.

How can I test the stator or if the spark is strong vs weak?

Sobie2
 
Well I read through some other posts and went out and bought a spark plug and it fired up and ran....

but it raced and the throttle and choke didn't seem to do much. So there must be some air getting into the system and maybe something else is clogged.

Sobie2
 
Lunch break update:

Motor will not stay running. Fuel is being pumped into the carb (I can drain it). Motor will run briefly with starting fluid (yes a no no really). I am thinking I need to soak the carb again. I couldn't get the main jet removed with the carb removed and float bowl off so that must be where my blockage is. A new carb and carb gaskets would probably work but that would have to be ordered (I am in Alaska). The local Tohatsu shop wouldn't order me one because they say a carb cleaning is all I really need (but they won't get to if for 2 weeks and their shop rate is $110/hr).... why would I not just buy a new one?

So I will rework the carb on my own and see what happens.

Sobie2
 
Your motor doesn't have a Stator. I'm guessing that the model is MFS4A2 (year is unimportant for servicing these motors). If it runs with ether, you have spark, and are short on fuel. Since you did not get the jet and emulsion tube nozzle out, you didn't get to really clean the carb. If you are successful in a complete disassembly, a proper 4-hour soak in real carb dip, followed by a spray-out with generic carb cleaner spray, it may be OK. Failing that, a new carb is in order. Since the only difference between the 4, 5, and 6 hp versions of your motor is the carb, if replacing the carb, go for the 6 hp carb. If you do end up needing a new carb, I would get 3R4032001M CARBURETOR ASSY, MFS/NSF6A2, $116.52, from any dealer, including me. I almost always have 1 or 2 of these carbs on the shelf, and can ship right away. Your local dealer should be able to get the carb in a couple of days, since FedEx pricing for Tohatsu America is very reasonably priced.

In the future, remember that modern North American "regular gas" is of generally poor quality, and often has 10% or more ethanol in it. Therefore, see if you can... get non-ethanol gas, consider running a good stabilizer in it, and always, always, run the carb out at the end of the day. If the carb is empty, you can't get any residue from fuel evaporation. In the case of an internal tank, when you restart, keep in mind that you will want a full tank, and will need a few minutes to allow the gas to make its way into the carb to refill the bowl before you will be able to start.
 
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