Need some help on a Mercury 125 hp outboard PLEASE!!

[fishincouple]

I NEED A BOAT/OUTBOARD Mechanic!!! PLEASE SHARE SO WE CAN GET BACK ON THE WATER ASAP!!!!!!!!!!!!! Here's the deal..97 Mercury 125hp, 2 stroke, 4 cylinder. All of a sudden stopped running. CAN start it and run okay for a little bit when choke is engaged. Plugs are good, got spark, fuel, oil in it....I'm lost now. Took airbox off; everything clean and looks good. Need someone that knows about these engines. I can offer some cash, trader/barter, trips to the lake/fishing/boating. HELP!! :) PLEASE SHARE!!

TY in advance..Fred

[sweetfish]

Check fuel filter and water / fuel separator.

[fishincouple]

Check fuel filter and water / fuel separator.

Will do! Thank you!

[enohserf]

Make sure your gas tank has ventilation. Your fuel pump may be sucking but if there is no circulation it could prevent gas from flowing freely causing the engine to die. Also your primer bulb should be mounted in a vertical position in order for the check valve to work properly.

[cutbait]

I'd it runs with choke on then it's not spark.

If it runs with choke on only it's starving for fuel

If it runs with choke on it cannot be running "ok"


Sounds like gummed carb, leaking fuel line, water in seperator, carb, or tank.

I suggest carb rebuild first.


Run this test.

Pull one plug. Squirt a little 2 stroke mix of fuel in the xylinder and replace the plug immediately. do not engage the choke. Try to start it. If it fires it's a fuel delivery issue.


Also get a cylinder pressure gauge and find your psi's

[fishincouple]

Thank you all for the info. I'm going to start with a fuel filter. I'll check the ventilation for the tank, and ensure the primer bulb is firm. BTW..now I understand that pushing the key in is NOT choking it, rather PRIMING it??? which could make a filter a reasonable fix?? IDK..Like I said..on the lake..ran fine..turned it off to dock up and now this..I'll report back in.

[cutbait]

Pushing the key is choke.

Priming is squeezing the bulb

[DEVOREFLYER]

If you have the original fuel line or fuel bulb it is likely not ethanol resistant. Does your fuel line have blue or red writing. If blue OK. If red.......change out. A1 or A2 are fuel lines that are ethanol resistant. The original grey fuel line from that vintage was not ethanol resistant. Ethanol will degrade the interior of the fuel line and will clog the fuel filter and fuel dependent parts.

[Hotbite909]

If it only run when the choke is engaged it is starving for gas and the the choke is compensating for the lean fuel. It is probably in the fuel delivery. Filter or the fuel line is is sucking air just enough to stop the fuel. Fuel line and priming bulb are problem a lot of the time. Replace the filter and fuel line first. It is not too expensive. Then work on the carb if needed. Also check you gas tank for water and dirt.

[DockRat]

http://forums.iboats.com

[enohserf]

I agree with the ethanol response. I forgot my Merc used to bog down but I switched to Chevron exclusively which has Techron vs. ethanol and I remember that I started getting better response from the engine. I'd swear by it. No ethanol anymore for my boat. If you have a clogged carb I have friends that recommend Quicksilver carb cleaner or Sea Foam. I have also changed the inline fuel filter but there is also an internal fuel filter inside the cowling. I believe it is along the fuel line after the fuel pump. Make sure you have zero leaks when replacing your filters.