2 stroke outboard starts but then dies when throttled or idle.

[Nicholson58]

Originally Posted by Bill O

Any of these are possible included a degraded fuel line. Some of the newer fuel lines do not play well w/ethanol fuel.


Here is an example of how the liner can come loose and heavily restrict/block fuel flow.

Correct on that one Mike. Marooned in the Hudson River once and again in a Michigan swamp when the OB quit. Both times was fuel line liner, different motors. Also lost the acceleration bellows three times on the Mariner 15. All due to ethanol. Replace any fuel lines with gas line purchased from a US auto supply and certified for E10 or higher alcohol.

Fortunately, this problem exists only in the US where we turn our food into fuel at a net negative system efficiency. In the Caribbean since 2016 and the OB has never run better.

[Lionshooter]

You said it never idled well and now dies when given fuel.
That is a classic symptom of an air leak, as several others have mentioned. And that can be a multitude of reasons, some obvious, others not so. I had one that a client had taken to two shops without luck. I found a slight depression in the fuel bowl gasket. A spot of RTV silicone had him up and running perfectly until I could get a new gasket.

[Nicholson58]

Consider adding one of these. Solved water and dirt in the gas.

[Cadence]

Originally Posted by paulg222

I have an 8hp Mercury 2 stroke outboard for my dinghy and it has generally been very good, but recently after having just filled the gas with 97 Premium (at Valero) and adding the appropriate oil, it is now not running.

This engine has never idled that well, but previously, as soon as it starts if I apply some throttle it is good to go. Now the exact opposite. It will start and as soon as I apply throttle it dies. Also if I leave it idling it also dies fairly quickly. But I can still get it to start again.

Theories:

• My outboard hates this premium Valero gas and refuses to run on it
• Something got dislodged in fuel line from the portable tank to outboard and is clogging up the works
• Spark plug? (but then why can I get it to start)
• Fuel pump issue
• Fuel filter issue

I have not tried squeezing the bulb after it starts to see if that helps keep it running, but I'll give that a try next. Note: the outboard is "pissing" water when it starts so probably not an overheating issue.

Looking for any other advice.

I would agree with a carb rebuild or at least a clean out. Have you been feeding it corn oil gas? Quickest way to gum up a small carb..

[Nicholson58]

Originally Posted by Lionshooter

You said it never idled well and now dies when given fuel.
That is a classic symptom of an air leak, as several others have mentioned. And that can be a multitude of reasons, some obvious, others not so. I had one that a client had taken to two shops without luck. I found a slight depression in the fuel bowl gasket. A spot of RTV silicone had him up and running perfectly until I could get a new gasket.

Air leak or fuel restriction. Result is the same when the throttle demands fuel.

[svfinlandia]

No one has yet mentioned a lack of airflow.
Three things needed for ignition - spark, fuel and air. If it has an air filter check it and see if it is clogged. Had a mouse build a nest in mine once.

Al, S/V Finlandia

[malross]

There may be a bit of water in the gas you got.Doesn't matter why.
- drain fuel bowl
- add a bit of Fuel Stabilizer or Seafoam
Wait a few minutes and try again.
Ethanol SUX
* if not, I would try NEW plugs.
I always cleaned and re-gaped until I swapped to New= World of Difference.
note- Check plug gap on New Plugs as I have had some Not with the right gap !
Good Luck

[team karst]

Make sure throttle cable advances the ignition plate under the flywheel. Could be plugged high speed jet? Who said air filter[emoji854]

[kryg]

I have a 2 stroke 4hp Yamaha in my case I has the same issues your discribed. it turned out not to be fuel - but small rust flakes that acumilated over time. My outboard did not have a fuel filter I had install it now since I had the mecanic clean out the fuel tank on the engine. I susspect the rust flaks came from the the gas station tanks as the the plastic jerry cans also on inspection had rust flakes sitting on the bottom of the plastic jerry cans.

Originally Posted by paulg222

I have an 8hp Mercury 2 stroke outboard for my dinghy and it has generally been very good, but recently after having just filled the gas with 97 Premium (at Valero) and adding the appropriate oil, it is now not running.

This engine has never idled that well, but previously, as soon as it starts if I apply some throttle it is good to go. Now the exact opposite. It will start and as soon as I apply throttle it dies. Also if I leave it idling it also dies fairly quickly. But I can still get it to start again.

Theories:

• My outboard hates this premium Valero gas and refuses to run on it
• Something got dislodged in fuel line from the portable tank to outboard and is clogging up the works
• Spark plug? (but then why can I get it to start)
• Fuel pump issue
• Fuel filter issue

I have not tried squeezing the bulb after it starts to see if that helps keep it running, but I'll give that a try next. Note: the outboard is "pissing" water when it starts so probably not an overheating issue.

Looking for any other advice.

[conchaway]

After you get it cleared, use NON ETHYNOL from now on-- only a donkey runs well on corn.

[Nicholson58]

For all - google search

Ethanol free gas near me

Ethanol, especially in older engines, is the kiss of death. I propose we put every legislator who forced this scam upon us into a RIB with an old enough OB and fifty gallons of ethanol fuel about 300 miles off shore with no radio or phone and let them go.

BTW, your standard kit in your dinghy should include an anchor, enough line, hand held radio, cell phone. Even a good motor can fail you and the tide and wind might just send you out.

[P3sailor]

A big part of me say's it's your carburetor main jet. The jet can become partially clogged/blocked and will allow startup and possibly idle but that is the extent of it. This has happened to me before, while the jet may look clear it doesn't take much to hamper the motor performance. Do not attempt to clean the jet with anything harder than the brass the jet is made of. I generally will use a piece of stranded copper from some old electric wire to perform the cleaning. Hope this helps.

[Bullshooter]

Originally Posted by Nicholson58

For all - google search

Ethanol free gas near me

Ethanol, especially in older engines, is the kiss of death. I propose we put every legislator who forced this scam upon us into a RIB with an old enough OB and fifty gallons of ethanol fuel about 300 miles off shore with no radio or phone and let them go.

I don't want to hijack the thread, but this is a pet peeve of mine. The ethanol hoax is based on the lie that it reduces CO2 inputs to the atmosphere. This ignores the diesel burned in planting and growing the corn, as well as the energy used in transporting and converting it to ethanol, (plus the admittedly less CO2 produced in using the ethanol). Rant over, carry on.

[C420sailor]

Start with the basics.

Check your linkages. Make sure the timing is advancing as you open the throttle.

Check timing.
Rebuild and clean the carb. New seals, new jets. If you can’t remember the last time it was done, it’s due.
Change and gap plugs.
Rebuild the fuel pump.
Check fuel lines for cracking.

[Cadence]

Originally Posted by Bullshooter

I don't want to hijack the thread, but this is a pet peeve of mine. The ethanol hoax is based on the lie that it reduces CO2 inputs to the atmosphere. This ignores the diesel burned in planting and growing the corn, as well as the energy used in transporting and converting it to ethanol, (plus the admittedly less CO2 produced in using the ethanol). Rant over, carry on.

It wasn't about CO2 it was about votes.