Mercury 3.3 Runs Then Stalls

[Tater]

I have just cleaned the tank. I blew out the carb and changed the fuel line. When I back flowed the fuel valve with cleaner very little came into the tank. I thought that was odd.

Now I filled the tank and cranked the motor. It ran great for about 15 seconds. I tried again and the same result except it runs less. The longer it sits, the longer it runs. This sounds like classic fuel starvation.

The fuel valve is assembled with a nut. Is there a filter inside the valve? The tube from the valve sticks up about an inch. I assume it has a slot or small holes to stop large contaminants.

 

[Rich Stidger]

On outboards that I have owned with an attached tank, there has always been a screen filter that attaches to the fuel valve and sticks up into the tank.
Remove the valve and disassemble the filter and clean in carb cleaner. If you can't separate the valve from the filter replace the entire unit.
Some outboards have a small in-line filter in addition to the tank screen. I would replace that one as well.

 

[Tom J]

My Mercury 3.3 did that every spring (think ethanol gas). I got tired of buying carb kits, and sold the Merc. I bought a Torqeedo.

 

[Tater]

On outboards that I have owned with an attached tank, there has always been a screen filter that attaches to the fuel valve and sticks up into the tank.
Remove the valve and disassemble the filter and clean in carb cleaner. If you can't separate the valve from the filter replace the entire unit.
Some outboards have a small in-line filter in addition to the tank screen. I would replace that one as well.

Thanks Rich. That valve is large enough to have an internal filter. I couldn't see the tube in the tank well. I'll try to clean it tonight.

 

[Tater]

My Mercury 3.3 did that every spring (think ethanol gas). I got tired of buying carb kits, and sold the Merc. I bought a Torqeedo.

Thanks Tom. I reserve hatred for very few things. Outboard motors are on that list. A small Minn Kota normally gets me out/in but I'm going to the beach. The motor isn't rated for saltwater.

 

[kloudie1]

Check that the tank cap vent is not plugged with bug stuff too.. Probably the valve but the vent is a quick and easy check .. Good Luck.

 

[Tater]

I (think) I am done.

The cap vent was OK. The filter/screen was not. It was nearly opaque. As I sprayed from the nipple the color changed and went nearly transparent with good flow. I reassembled the tank and tried the motor. It ran then quit. This time it did something it has done before. It wouldn't even sputter. I gave the carb another shot of cleaner but no joy. Step 1 is fuel. Step 2 is ignition. I pulled the plug, and it was wet. I found a small engine plug in the toolbox and installed it. It had a nice sound for about 5 minutes and then I was able to drain the bowl. I see a visit to the auto parts store coming.

I spent too much of my childhood at the lake or on it while dad worked on the motor. I have a hatred for outboards.

Thanks All

 

[Rich Stidger]

If you had that much gunk in/on the tank filter I would suspect that there is more in the carb.
Spraying cleaner into the throat of the carb only removes surface deposits. Cleaning the internal carb passages and jets are critical for proper running.
If you also suspect the ignition, then that would be the next area to check. You can get a spark gap tester to put in line with the spark plug for testing the spark quality.
If you still have running problems then I would pull the carb and install a rebuild kit. Spray carb cleaner through all of the internal passages. If you have an ultrasonic cleaner, fill it with carb cleaner and process the carb for 30 minutes.
If you are not using E0 gasoline, get some and use it exclusively. The use of E0 gas will prevent almost all fuel problems.
I also hate outboards and all other small engines.

 

[Tom J]

The use of E0 gas will prevent almost all fuel problems.

Essential for carbureted engines.

 

[Tater]

Thanks Rich and Tom. The thing is that the tank was clean. I soaked it in Seafoamed gasoline just to be sure then chased that with cleaner. The filter was the thing. When I bought this boat it came with the 3.3. The seller had recently put it in the shop for the sale. (I have that invoice.) I think the carb was clean also, but it was cleaned thoroughly from dip-tube to venturi. I blew it out from the mixture screw hole also. I'm guessing the tech didn't take much time with the motor. I run only E0 premix in all of my 2 cycle engines. The others use pickled fuel.

When I tried the motor in October it ran great then quit. I had a backup electric on the boat and got back in with it. I drained all the fuel and set the 3.3 aside. Now, I have two problems, one that is intermittent. The motor ran great with the test plug. I'll get a new plug today and give it a good test tomorrow on the water. I will take an electric for backup.

The cost of a spark plug is about as far as I will go with this motor. That money would be better spent on a saltwater electric.

 

[Tom J]

Thanks Rich and Tom. The thing is that the tank was clean. I soaked it in Seafoamed gasoline just to be sure then chased that with cleaner. The filter was the thing. When I bought this boat it came with the 3.3. The seller had recently put it in the shop for the sale. (I have that invoice.) I think the carb was clean also, but it was cleaned thoroughly from dip-tube to venturi. I blew it out from the mixture screw hole also. I'm guessing the tech didn't take much time with the motor. I run only E0 premix in all of my 2 cycle engines. The others use pickled fuel.

When I tried the motor in October it ran great then quit. I had a backup electric on the boat and got back in with it. I drained all the fuel and set the 3.3 aside. Now, I have two problems, one that is intermittent. The motor ran great with the test plug. I'll get a new plug today and give it a good test tomorrow on the water. I will take an electric for backup.

The cost of a spark plug is about as far as I will go with this motor. That money would be better spent on a saltwater electric.

I feel your pain, Tater. I got very frustrated with the cost and availability issues of the carb kits for the Merc, and, in the end, the kits were junk compared to back in the day.
You don't say how old the 3.3 is, but, if it was run for some years on regular gas, and then switched to E10 at some point, the E10 would clean all the varnish off the inside of the tank and deposit it the fuel filter, carb, etc.
I think you would be very happy with the saltwater electric (Torqeedo). You wouldn't have gasoline stored in the cockpit, and no more premixing. You would have the same HP available at the push of a button. You would be motoring in a quiet, conversation friendly environment. You would get days of use on a single charge, motoring in and out of your slip, or quite a few miles motoring home on a calm day. The built-in computer will tell you state of charge, and the range left at present speed. At the end of the day, you could pop the battery off the top of the outboard, and take it home to charge it. You could then pull the leg of the outboard off the transom and store it inside if you wish. The full torque of the motor is available form 0rpm, and will get you into and out of your slip with ease. Oh, and the Torqeedo is waterproof. You can drop it into the water, and then go motoring (after you retrieve it).
Anyway, I guess you can tell I love my Torqeedo. There is a reason a lot of production sailboats in your size range come equipped with a Torqeedo. The investment is well worth it!

 

[Tater]

Tom, I was able to locate the plug with some difficulty. It apparently isn't a common one. It did cross to an Autolite.
The motor ran fine on a short thread line trimmer plug. A correct plug should do even better.

The Torqeedo is a little much for my needs. For now Minn Kota will do. Thanks.

FWIW, the wife and I passed through Quincy in October. We did a lighthouse tour from far Down East ME to Cape Cod then on to the Outer Banks.

 

[Benny17441]

Ethanol gas is gumming up the carburetors. Disassembling and cleaning the carb usually resolves the problem but in instances a new carburetor is necessary. Obviously make sure you have good fuel flow coming out of the tank.

 

[Tater]

Thanks Benny. I only run E0 premix. This thing had two problems. A dirty fuel filter and an intermittent spark plug. The filter was easy enough once I got deep into the problem. The plug drove me crazy. The original plug was an NGK BPR6HS-10. Best I can tell this is the correct plug. I couldn't find a replacement. It crosses to an Autolite 4123 which was available.

The big question: I read at NGK that CDI systems will destroy a standard resistor type plug. I don't know what the original was. I don't know what the Autolite is. I couldn't find a non-resistor plug. I have a headache from too much screen time. All that being said, I bought a spare plug and keep a plug wrench in the tool kit.

I may know more later today. l am going sailing.

 

[Tater]

I was becalmed today after wind was promised. The 3.3 ran hard for well over an hour total. I am good for the beach.

The wind did come in late. It was strong and a little shifty but fun just the same.

 

[Rich Stidger]

<snip> The original plug was an NGK BPR6HS-10. Best I can tell this is the correct plug. I couldn't find a replacement. It crosses to an Autolite 4123 which was available.
<snip>

I buy my NGK plugs from a local auto parts store that is now part of Advance Auto. I don't normally find NGK at places like WalMart. An IIRC the BPR6HS-10 is the same plug I use in my Nissan 3.5. I believe that my engine and yours are based on the Tohatsu design and share many common parts.

 

[Tater]

Thanks Rich. Advance and O'Rielly could order it. The Autolite may outlast the motor. Time will tell.