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2001 Mercury 125hp 2 stroke questions

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Been a long time since I have been on here, but its winter and I am getting my boat fixed up for next year and have some questions. I have a 2001 mercury 125HP 2 stroke. Have never found a good way to start the thing. I pretty much consider myself an expert at starting all sorts of equipment from weedeaters to bobcats, but this boat has me puzzled. 

 

Usually a small engine like this, I would prime the bulb a few times but not so much that it forces too much fuel in, then turn the choke on and turn over until the engine sputters or starts, upon the first sputter the choke comes off, then the engine should start right up. That sequence works for every small engine I have ever started. 

I have tried all sorts of sequences  and combinations ( high idle with choke, high idle without choke, choke, no choke, etc). This motor still takes several minutes to start. It has always started eventually, but in my mind takes way to long to do so and is hard on the starting battery. 

 

Also the next problem, once it is running if I shut it off for more than 10-20 minutes it will be back into the same situation, hard starting. 

 

I plan on putting new spark plugs in, and contemplating a carb rebuild. I have rebuilt enough carbs that I know how, but also know that they seem to always have a problem of a screw not wanting to come loose or something dumb like that. I am afraid to tear into something that is usable, but not to the standard that I think it should be. 

 

Anyone had this experience with this year of motor?

 

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6 cylinder inline engine?

Change the gasoline filter, new fuel line and prime bulb, new spark plugs** after you spray warm water* into the carbs while the engine is running about 2,000 rpm's. It's a few decades since I have worked on this engine so my memory is a little fuzzy, you should have 2 ignition power packs, 1 for each 3 sets of cylinders and 3 carbs, 1 carb for a set of 2  cylinders.

If you have a manual choke ( I don't think you do on a 2001) you can operate it. I recall only 1 carb and 2 cylinders get choked.  You should have a electric choke with the start key turned to prime the carbs, you can hear the fuel supply run.

Use your prime bulb to squeeze gasoline into the carb bowls, difficult to flood a 2 stroke.

Turn the key and listen for the fuel to prime the carbs and start your engine, shouldn't turn over more than 10 seconds without starting to run on it's own.

**Check the plugs, they should be tan color not black.

* the sprayed water cleans out any carbon build up and will tend to stop the engine if you spray too heavily. You can follow up using Quick Silver Power Tune spray. This should be done at home and need to use water hose with ears to run water through the engine doing this as the exhaust will blow out carbon.

Good luck.

Tom

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How old is the gasoline in the tank?  Do you use a fuel stabilizer?  Today's gasoline starts degrading in a few weeks, maybe as little as two.  

 

I have a lawn edger that will not start in the spring with old gas.  Drain it.  Put in new gasoline and it will start on the first pull.

 

I treat all fuel that I put in jugs for all lawn and garden equipment.  The lawn edger will start right up with last year's fuel that has been treated.  I use Stabil.  Others use different brands with success for preventing fuel problems. I also use it in the emergency generator.  That's probably the most important of all our gasoline powered equipment.

 

I also treat all fuel that I put in the boat's fuel tank, not just dumping fuel treatment in the tank when the boat is winterized.  Fuel treatment also helps to slow the damage to fuel lines.

 

The only gas that doesn't get treated is what goes into our vehicles.  A tank of gas will last a week during the fishing season, two to three weeks during the "off season".

 

"Stale" gas is probably the most common cause for starting problems.

 

Google "stale gas, starting problems", and see what you get. 

 

 

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Those carbed Mercs have always been a bear to cold start.  If all of your maintenance is up to date and it's not something mechanical causing your hard starting, then everyone I know who has one has a special sequence they go through to start them, especially a cold start.  You just have to find out what works for your motor.  That being said, you do need to check all of the normal culprits for hard starting, Primer Bulb, fuel lines, fuel quality, plugs, carbs, battery, etc.  If everything checks out then just experiment with your starting process until you get it.  

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20 hours ago, WRB said:

6 cylinder inline engine?

Change the gasoline filter, new fuel line and prime bulb, new spark plugs** after you spray warm water* into the carbs while the engine is running about 2,000 rpm's. It's a few decades since I have worked on this engine so my memory is a little fuzzy, you should have 2 ignition power packs, 1 for each 3 sets of cylinders and 3 carbs, 1 carb for a set of 2  cylinders.

If you have a manual choke ( I don't think you do on a 2001) you can operate it. I recall only 1 carb and 2 cylinders get choked.  You should have a electric choke with the start key turned to prime the carbs, you can hear the fuel supply run.

Use your prime bulb to squeeze gasoline into the carb bowls, difficult to flood a 2 stroke.

Turn the key and listen for the fuel to prime the carbs and start your engine, shouldn't turn over more than 10 seconds without starting to run on it's own.

**Check the plugs, they should be tan color not black.

* the sprayed water cleans out any carbon build up and will tend to stop the engine if you spray too heavily. You can follow up using Quick Silver Power Tune spray. This should be done at home and need to use water hose with ears to run water through the engine doing this as the exhaust will blow out carbon.

Good luck.

Tom

sounds like good advice...except spraying water into the carbs?! are you pulling my leg?

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No, it's an old racers trick. If you are uncomfortable doing it, use the carb cleaners.

Tom

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13 hours ago, TOXIC said:

Those carbed Mercs have always been a bear to cold start.  If all of your maintenance is up to date and it's not something mechanical causing your hard starting, then everyone I know who has one has a special sequence they go through to start them, especially a cold start.  You just have to find out what works for your motor.  That being said, you do need to check all of the normal culprits for hard starting, Primer Bulb, fuel lines, fuel quality, plugs, carbs, battery, etc.  If everything checks out then just experiment with your starting process until you get it.  

Thanks for the reply, I will do all the basic maintenance and see if it helps at all. I have known one other person with the same motor and his did have a few quirks about it as well, just not as bad as mine. 

 

As for the gas, right now it is getting old, I filled it up on fourth of july, but the same problem persists even the days that I fill up full of fuel (20 gallons so it should offset a gallon or two of old fuel) and I always use stabil with every fill up. 

2 minutes ago, WRB said:

No, it's an old racers trick. If you are uncomfortable doing it, use the carb cleaners.

Tom

Just googled it and see what you are saying. Learn something new every day. Thanks for the tip. I'm going to do some more research before trying it as its pretty scary to think about putting water into a running engine. I am not well educated on internal engine anatomy, just remember reading about using seafoam and lots of people claim you can hydrolock the engine by putting it directly into the engine.  

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Light spray into the carbs while the engine is running, just a few squirts from a spray bottle and it's creates high humidity with oxygen. You will not hydraulic the running engine by spraying into a carb.

Tom

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after looking over the engine for part numbers and inspecting condition of lines/hoses, I notice a yellow wire coming from what looks to be a computer box, or electrical box of some kind the yellow wire is burnt in the butt connector. can't tell if its burnt in two but the butt connector is supposed to be clear and this one is all charred, the other wires around it were stuck to it (butt connectors were stuck since they seem to be a rubber like material)

 

guess I will find a wiring diagram and see what this wire goes to. 

 

For the record it is 4 cylinder 4 carburetor. 

And the back/sides of the carbs have oil on them, especially the bottom carb. and the foam on the inside of the cowling is soaked with oil in spots. The oil system has been removed by the previous owner and I use mix gas in the tank. So I don't think it is from spilling oil in the engine compartment. 

 

 

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That's an old trick that has been around for years.  During WWII, they had water injection in piston airplane engines they could use for an instant burst of power, but the engine was rebuilt after using it.  Mechanics have used it on engines just before rebuild teardown to de-carbon them.  It does cause a significant compression spikes that can break rings and cause damage parts so it's not something I would recommend doing to a perfectly good engine.  If it was a good thing, drag racers would be using it instead of nitrox oxide.

 

As for trouble shooting your problem, first you need to find out if it's fuel or fire. 

I would start by manually spraying pre-mixed gas in each carb and see if it starts up easily.  If it does, that shows it's not getting enough fuel.  If it's still hard, it could be getting too much fuel or have a weak spark.  A spark checker would be handy now to make sure each cylinder has a strong blue spark.

Not know a lot about Mercs. does that motor have a choke or primer system.  A choke has butterflies that close off the carb venture.  A primer has a solenoid valve that opens and lets fuel go directly into the intake.  If it's primer, the solenoid my not be working.

Also, make sure when you pump the primer bulb, you pump until it's firm, if it's not getting firm, you need to find and fix that problem.  A primer bulb valve, or carb could be leaking by.

 

I just read your last post, if you run a two stroke without a good tight seal on the air silencer, you will get gas inside the cowl.  By the nature of the way they work, that have a right smart of blow back that comes out of the carbs when it running, so if it's not confined, it makes a mess.

 

Oh, and that butt connecter being burn, means it is not making a good connection and causing a resistance, that resistance it what's causing the heat that burning the wire/connector

 

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Good response above from Way2Slow as always.

Spraying water mist to clean carbon isn't the same as water injection and 2 strikes don't have rings to break. 

Back in the day when I was racing alcohol burning outboards carbon was never an issue, the older inline 6's on mixed gas/oil were and after each marathon run were would de carbon those engines to clean off the top of the piston, it doesn't do any damage. The drag days we ran a mixture of nitro/alcohol and sometimes benzine, engine longevity was about 1 weekend if you were lucky! The days of shade tree mechanics is long gone, we still made 500 hp per cylinder back in the 70's in AA fuel cars.

Getting way off topic.

Note if you decide to spray gasoline into the carb be careful, gasoline is very volatile fuel when atomized.

Tom

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