Mercury 3.3 2-stroke Carb issue?

[jonelli]

I know these are generic motors, Tohatsu, Mariner, etc... And I've got the service manual. But, before I remove or replace the entire carb, I want to be sure there isn't something else I can do first, so I'd like to ask for some advice.
Here's the issue I can describe:

It will start up GREAT. it idles PERFECT. I can rev it full RPM in neutral. But if I am in gear, anything above 1/3rd RPM power, it acts like it will stall INTERMITTENTLY.
For example, I start it up, and put it in gear, and give it some gas. It will go full power for about 10 seconds and then slowly start to lose power over another 20 seconds until it dies, or sometimes when I go full power, it dies immediately. If I play with the choke while it's starting to die, it revs up to full again for a few seconds and then MAYBE sill stay at full RPM, but usually won't. It will run forever in gear in low RPM.
It started recently, and it was well after being left alone for a few months (Probably not properly emptied). I had been using it recently at full power just fine, and it was all of a sudden it started to act like this.

I read that the small motors have a filter built into the fuel cock? Is that right? The service manual says it should be replaced if it's clogged or damaged.
Obviously, I could try bypassing it, but if it's a problem in the carb, is there somewhere I can just try spraying some cleaner and "running it through", or something I can run through the fuel to clean it? Techron? Something else?

Looking for the easiest most reliable solution. I don't want to pay $40 for rebuild kit and spend 5 hours or more of my time when I can buy an aftermarket entire assembly for $82 on Amazon. But, I don't want to do that either if there's a $5 cleaner I can try first.

Thanks all as always for the advice.

 

[chuckwayne]

it's probably crud from the ethanol gasblocking flow, either in the filter or the high speed jets. I've used sea foam with success in my 3.3;I'd feed it fresh gas with a lot of it mixed in, run it for a while, let it sit/soak and then run it again.

 

[Rich Stidger]

My 3.5 Nissan (basically the same Tohatsu) used to perform in a very similar manner. It would start and run fine at cruise speed and then just die. Maybe it would start again quickly or maybe not. It drove me nuts.

I tried Seafoam with no positive results. Changed plug, fresh gasoline, same problems. Spraying carb cleaner into the air opening will only clean the intake surfaces and the choke plate. You might feel good, but the engine will still perform badly.
After speaking with a friend who owns a marina on a local lake, and who does repair and maintenance on all kinds of engines, he told me how to accomplish "The Final Fix".

In a nutshell the problem is the ethanol gasoline that we are forced to use in most areas. The ethanol absorbs water. The water causes aluminum corrosion. The corrosion (a white powder or surface coating) clogs the extremely small holes in the jets and carb passages. This is more likely and serious in 4-cycle engines than in 2-cycle engines due to the 4-cycle smaller sized passages. Engines under 10hp are the ones that are particularity prone to these problems. Large outboards or other engines don't have this problem because the carb passages are much larger.

For 2-cycle engines: "The Final Fix" - Remove the carb and disassemble completely. Soak all parts overnight in a carb dunk solution. Blow out and through all passages with spray carb cleaner. Re-assemble.
For 4-cycle engines: Due to the extremely small passages, just soaking in a carb dunk solution won't cut it. What needs to be done after complete disassembly is to put all of the parts in an ultrasonic cleaner with the carb dunk solution and clean for some period of time. Then blow out and through all passages with spray carb cleaner and re-assemble.

Although my engine, like yours, is a 2-cycle engine, I pulled out all the stops and used an ultrasonic cleaner. I ran the solution heated to 50 degrees C for 30 minutes. Blew out and re-assembled.

Now for the prevention: Buy and use ONLY NON-ETHANOL gasoline. I travel 15 miles to the nearest station that sells this gasoline and I buy 5 gallons. I use it in my outboard and all of my small engines- string trimmer, leaf blower, chainsaw, etc. I add Stabil to it immediately after purchase. When I buy the fuel, I first put a gallon into my car to purge the pump hose from whatever was pumped before I arrived. Then I know I have 100% E0 gasoline. At the end of the season I dump any remaining E0 fuel in my 20hp lawn tractor. Any small amounts of 2-cycle mix is just discarded.

Problems gone. Now all my engines run great.

 

[jonelli]

For 2-cycle engines: "The Final Fix" - Remove the carb and disassemble completely. Soak all parts overnight in a carb dunk solution. Blow out and through all passages with spray carb cleaner. Re-assemble.

Thanks for that info.
And there's my issue... Carb dunk solution is $30. Any parts if I need them is another $30 for a "kit". To remove, disassemble, soak, and reassemble, will take it bit more work than $82 to just put a new one on that I already know is clean.

So, I think I'm going to try the seafoam/cleaner ($10) method first and see if it makes it any better, and if not, just buy a new one.
But, if it's the filter in the fuel cock, then I'll be in the same boat.

 

[rgranger]

What @Rich Stidger said about E0 gas AND! When you return to the dock disconnect the fuel line with the motor still running at idle and let the engine die. That will use up the 1/4 cup of gas in the carb bowl so you won’t have gas sitting in the engine. In theory this should be sufficient for ethanolated gas too but like Rich... I drive out of my way to buy EO.

As the E10 gas sitting in the carb bowl evaporates over time, the ethanol becomes more concentrated and ethanol can absorb water out of the air. This causes the metals in your carb to oxidize. So running the carb dry after each use is a good practice.

 

[RoyS]

for E0. Use it in all my small engines. This after having to replace the carburetors on my snowblower and outboard a few years ago. Ethanol has no business in gasoline engines. Recently read that people with electric cars that have a backup gas engine as well are finding that the backup will not start due to ethanol break down over time. I have a generator in my garage with five gallons of unusable E10 in it that I have to deal with. Uggh.

 

[Rich Stidger]

<snip>
But, if it's the filter in the fuel cock, then I'll be in the same boat.

The fuel filter is very easy to check- at least on my Nissan version. A hose clamp removed the fuel cock and the filter is pressed into the top of the valve. Easy to clean if clogged.

 

[Rich Stidger]

What @Rich Stidger said about E0 gas AND! When you return to the dock disconnect the fuel line with the motor still running at idle and let the engine die. That will use up the 1/4 cup of gas in the carb bowl so you won’t have gas sitting in the engine. In theory this should be sufficient for ethanolated gas too but like Rich... I drive out of my way to buy EO.

As the E10 gas sitting in the carb bowl evaporates over time, the ethanol becomes more concentrated and ethanol can absorb water out of the air. This causes the metals in your carb to oxidize. So running the carb dry after each use is a good practice.

You are correct. At the end of the day I shut off the fuel valve and run the engine for 1-2 minutes until it dies. I forgot that detail.....

 

[jonelli]

You are correct. At the end of the day I shut off the fuel valve and run the engine for 1-2 minutes until it dies. I forgot that detail.....

I'm not as religious about that. I will be from now on though.

 

[shemandr]

I had basically the same problem with my Nisson 3.5. Drove me nuts. Finally I replaced the carb bowl and if I remember the high speed jet. I also put in an aftermarket inline fuel filter and replaced those spring fuel hose crimps with hose clamps in case they were leaking air. All that cured the engine. It was as Rich said. Little flecks of the aluminum oxide from the bowl were clogging the jet.

 

[jonelli]

I had basically the same problem with my Nisson 3.5. Drove me nuts. Finally I replaced the carb bowl and if I remember the high speed jet. I also put in an aftermarket inline fuel filter and replaced those spring fuel hose crimps with hose clamps in case they were leaking air. All that cured the engine. It was as Rich said. Little flecks of the aluminum oxide from the bowl were clogging the jet.

Can you point to which jet you replaced?

 

[Davidasailor26]

For my 2 cycle engines I follow the procedure Rich describes, though I don’t soak in cleaner overnight, I just disassemble and spray everything I can with carb/ choke cleaner, wipe, and reassemble. That pretty much always has worked for me. One small weed wacker engine still needed to be partially choked to run properly. Last year I started using SeaFoam and since then none of my engines have had any problems. Even the weed wacker runs perfectly now without any choke. I do still try to run the carb’s dry on all engines that have a shutoff. On ones that don’t, like the lawn mower, I just run them dry at the end of the season. E0 isn’t available around me, but I’m very happy with SeaFoam so far.

 

[chuckwayne]

Rich,
great description of the problem! The Seafoam always seems to work with the 3.3 - but on my 5hp 4 cycle my mercury dealer just gave up on cleaning the carb, too many redos. I'm on my second carb, always try to drain the fuel bowl, but it's clogged again. What do you use for an ultrasonic cleaner? The admiral told me she'd kill me if I touched hers.

 

[Rich Stidger]

What do you use for an ultrasonic cleaner? The admiral told me she'd kill me if I touched hers.

Wait until she is asleep. Hide all the knives and rat poison. Pray for forgiveness.

Seriously, I bought a 2 liter cleaner on eBay about 4 years ago. At the time it was about $60-65 but it is higher now. When I bought it I really only had one carb that I wanted to clean. But after purchase I have cleaned every carb for my small engines and I use it for other de-greasing and cleaning tasks. 2 liters is large enough for a small engine carb (automotive carbs if you still have one are too large). It is all stainless, heats to a programmed temp setting, and you can time the length of cleaning time. And you wouldn't need to worry about your wife offing you.

Here is a picture of my unit:

The eBay link is: 2l Qt Ultrasonic Cleaner 110w Digital Heated Industrial Parts | eBay

Here is a picture of my Nissan carb BEFORE cleaning:

Spotless afterward.

 

[jonelli]

Okay, bought some Seafoam, put a bunch in with the tank empty, filled it about 3/4 full and have been running it.
actually, first I thought I’d try cleaning the bowl out since it looked like two screws. It after losing my screwdriver overboard and realizing I can’t get just the bowl out without more disassembly I stopped and put it back. Added the Seafoam and more fuel, then ran it slow, fast, back and forth through the harbor. Let it sit for an hour and did it all again.
it definitely runs now at WOT and doesn’t die.Now the only symptom seems to be when you let it idle for a minute then give it WOT, it dies immediately. If I slowly and gradually let it get to full throttle it seems to be okay and will run full without dying. This was not the case last time I was at the island. Previously it would randomly die at any moment or not even get to full throttle.
Is there any way of removing the bowl to clean it out without taking it all the way out?

 

[jonelli]

So, went out again running it up and down. Took it WOT to the end of our harbor. It was getting dark. On the way back, it started to die at high speed like before. Started back up once, then died again. Hmmm. Ran out of gas this time!!! Oops. One of my oars broke last weekend so I had to paddle back with one oar about a mile. Weather was nice though and got my exercise.

 

[rgranger]

It is a small motor. Take it home with you and work on it without the stress of dropping tools overboard.

 

[Rich Stidger]

<snip> Now the only symptom seems to be when you let it idle for a minute then give it WOT, it dies immediately. If I slowly and gradually let it get to full throttle it seems to be okay and will run full without dying. This was not the case last time I was at the island. Previously it would randomly die at any moment or not even get to full throttle.
Is there any way of removing the bowl to clean it out without taking it all the way out?

Poor acceleration (including dying) from idle is a symptom of the idle mixture being too lean. Try turning the idle mix needle 1/8 turn CCW at a time and then try to accelerate. Continue to richen until the acceleration is smooth. If you can't get it to accelerate properly after turning a couple turns, you probably have crud in the idle passages. This usually means a disassemble and clean as I have described above. However, once I was able to correct this same problem on a snowblower by taking out the low speed needle and spraying carb cleaner with a plastic tube directly into the port where the needle was. YMMV.

I can't help with removal of the bowl becasue I am not familiar with your exact engine.

 

[Rich Stidger]

Can you point to which jet you replaced? View attachment 182045

Attached is the Nissan document that is essentially the same engine. See pages 15-18 for the pictorial like yours and a listing of the parts. I couldn't extract just the pages you need so you are getting everything. Hope this helps you.

 

[jonelli]

Poor acceleration (including dying) from idle is a symptom of the idle mixture being too lean.

yep. That solved the acceleration issue.
I ran more Seafoam through it. It doesn’t die now. Seems reliable for the moment.
thanks.