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Old 09-05-2022, 13:05   #1
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Wit's end with my outboard part 2

So, many of you helped me out a month or two ago diagnosing problems with my outboard (6HP Tohatsu, using the internal tank. Just about a year old). I got the carb cleaned out (4 or 5 times by the end), got my fuel lines cleaned out, and everything was running great. Until it wasn't anymore. But now I'm much more familiar with the little bastard, so I think, "Yeah, I can handle this. I know what I'm doing now." HA! Pure hubris that thought was!

So now for the saga of what I've done to it this time. Beware, it's a long 'un. Specific questions are at the very bottom for those who only want to skim.

It was running fine, but then abruptly started having a problem where whenever I tried to throttle up, it would die. Occasionally, I would get it to rev up and drive, but then the power would be all over the place, surging and waning every few seconds. Most of the time, it would simply stall and die when I tried to open up the throttle.

A bit of Googling, and an old thread from this very forum has me convinced that the carb must once again have a little something in it. Supposedly, a little debris in the high-speed jet could cause it to fail to transition from the low-speed jet.

So I break down the carb again and have a good close look. And what do you know? There's a little bit of some kind of fiber in the high-speed jet. Like a short hair or something. So I clean that out, give the whole carb a thorough once over while it's out, and put things back together with all the confidence of a toddler in a Batman shirt. "I've solved it!" I mutter to myself, absolutely filled with pride at conquering a simple bit of maintenance.

Except. It won't start now. So I start looking over my work. I must have missed something on the reassembly. But it all sure looks right. I reference some photos I took before taking it apart. Yep, all looks good here.

So it's back to basics now. Why won't it start? Do I have a spark? I spray some starting fluid in with the spark plug. It lights that off no problem, but the engine doesn't run. Do I have air? Well yeah. It's just a simple little rubber hose to let air in. I take the hose off and make sure there's nothing blocking it. All good. So it must be fuel. Sure enough, I'm not getting any fuel to the carb anymore!

Well what the $&%! What changed from when it was running, just not right, to now? I had of course shut off the fuel valve before taking the carb out, but it was open again. I start taking off hoses.

Not only am I not getting fuel to the carb. I'm not getting it to the fuel pump either! That's odd. Gravity should have pushed fuel to the bottom of the pump. I keep working my way upstream, trying to find the gas. It turns out, even the very first hose connection after the internal fuel tank is devoid of any actual gas. Hmmmmmmm.

Suddenly, inspiration! The vent cap on my fuel tank isn't properly allowing air to flow. So the fuel is vacuum-sealed in the tank and can't run down the hose! I take the fuel cap all the way off, and fuel starts streaming out the hose!

I'm once again on top of the world! It was a tricky one to spot, but I found the problem. This was probably the real reason I couldn't throttle up as well! When I asked for that much gas, it couldn't pull enough out of the tank because of the vacuum seal, so it stalled! I start putting all the hoses back on to really test my theory. I quietly chuckle to myself, thinking "it's a good thing cool heads prevailed. All I had to do was go slow and methodical, and not get frustrated. I'm such a genius and all-around capable guy!"

I go one by one on the fuel hoses. Each time I reconnect a hose, I open the fuel valve and ensure a little gas dribbles out the far end. I get back to the fuel pump. I hook that back up and give the cord a pull. A little gas comes out of the top of the pump, I'm in business! I hook the hose back onto the carb, the final connection!

I give her a good 5-10 pulls. It makes sense it wouldn't start immediately. The carb is dry and I have to work a little fuel into it first. But after 10 pulls, I'm still getting nothing. No cough, no nothing. Hmmmmm.

I unscrew the little drain in the bottom of the carb bowl. Nothing comes out. Curioser and Curioser! I know I'm pushing gas into the carb. But it's not making its way into the bowl.

I know! That damn float valve must not be working right. The carb isn't letting any fuel in! So the carb comes off once again. I have a real close look at that float valve, but it seems totally fine! But I'm struck by a clever idea. I put the carb back on the engine, but with the bottom half of it still taken apart. The float valve now hangs down in the open air, with no bowl underneath it to float it up. I put a little cup under to catch the gas, and open the fuel valve.

Boom! fuel dribbles out the float valve just like it's supposed to! I use my finger to "float" the valve closed, and the fuel stops just like it's supposed to! Now I'm really and truly confused. If the float valve is operating correctly, and I can get fuel to run out into the open air where the bowl normally is, why was the bowl empty when I unscrewed the plug?????? Maybe it was just a little stuck, and I have it freed up now?

I reassemble the whole thing and give it one more try. Still nothing. Still no fuel in the bowl on the carb! And that moment was the titular end of my wit. My wit could go no further. I had reached the extent of the reach that could be provided by my wit. And so I put a couple of questions to the infinite wisdom of the forum:

1. What the heck is happening here? Is the float not able to move freely in the bowl? It looks like it should, but I can't actually see in there when the bowl is on to know if the float is moving.

2. Is my hypothesis about the vent cap reasonable? Could that have been the main problem all along?

3. What does one do about a vent cap that doesn't let air in? I can run with the cap off, but not if there's spray or rain. Replace the cap altogether?

4. Back to the carb: is it even worth continuing to mess with it, or should I just buy a replacement carb? Anybody have a good source for one?
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Old 09-05-2022, 13:16   #2
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Re: Wit's end with my outboard part 2

Just bought a new carb for my Honda 2.3hp. £70, wasn't worth faffing around with it, but then it is 15 years old.

You might put one of those in line filters in the fuel line so you don't clog the carb up in the future. I use one on my Suzuki SV650 with good effect.

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Old 09-05-2022, 13:21   #3
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Re: Wit's end with my outboard part 2

It could be the float assembly is bent or adjusted wrong and the float level is effectively set to keep the bowl empty (but removing the bowl allowed it to drop far enough to permit flow).
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Old 09-05-2022, 13:28   #4
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Re: Wit's end with my outboard part 2

Quote:
Originally Posted by rslifkin View Post
It could be the float assembly is bent or adjusted wrong and the float level is effectively set to keep the bowl empty (but removing the bowl allowed it to drop far enough to permit flow).
That actually makes a ton of sense! The hinge that comes out to allow access to that valve when I was cleaning was quite stuck and need a lot of force to move it. It's entirely possible I could have bent the little spring in the process. I guess I'll either get it bent back nicely so it runs, or buy a new carb.

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Old 09-05-2022, 14:24   #5
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Re: Wit's end with my outboard part 2

Sometimes it makes sense just to buy a new carb...especially since most small engine carbs are inexpensive.

And a new fuel tank cap...
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Old 09-05-2022, 14:32   #6
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Re: Wit's end with my outboard part 2

Quote:
Originally Posted by JebLostInSpace View Post
So, many of you helped me out a month or two ago diagnosing problems with my outboard (6HP Tohatsu, using the internal tank. Just about a year old). I got the carb cleaned out (4 or 5 times by the end), got my fuel lines cleaned out, and everything was running great. Until it wasn't anymore. But now I'm much more familiar with the little bastard, so I think, "Yeah, I can handle this. I know what I'm doing now." HA! Pure hubris that thought was!

So now for the saga of what I've done to it this time. Beware, it's a long 'un. Specific questions are at the very bottom for those who only want to skim.

It was running fine, but then abruptly started having a problem where whenever I tried to throttle up, it would die. Occasionally, I would get it to rev up and drive, but then the power would be all over the place, surging and waning every few seconds. Most of the time, it would simply stall and die when I tried to open up the throttle.

A bit of Googling, and an old thread from this very forum has me convinced that the carb must once again have a little something in it. Supposedly, a little debris in the high-speed jet could cause it to fail to transition from the low-speed jet.

So I break down the carb again and have a good close look. And what do you know? There's a little bit of some kind of fiber in the high-speed jet. Like a short hair or something. So I clean that out, give the whole carb a thorough once over while it's out, and put things back together with all the confidence of a toddler in a Batman shirt. "I've solved it!" I mutter to myself, absolutely filled with pride at conquering a simple bit of maintenance.

Except. It won't start now. So I start looking over my work. I must have missed something on the reassembly. But it all sure looks right. I reference some photos I took before taking it apart. Yep, all looks good here.

So it's back to basics now. Why won't it start? Do I have a spark? I spray some starting fluid in with the spark plug. It lights that off no problem, but the engine doesn't run. Do I have air? Well yeah. It's just a simple little rubber hose to let air in. I take the hose off and make sure there's nothing blocking it. All good. So it must be fuel. Sure enough, I'm not getting any fuel to the carb anymore!

Well what the $&%! What changed from when it was running, just not right, to now? I had of course shut off the fuel valve before taking the carb out, but it was open again. I start taking off hoses.

Not only am I not getting fuel to the carb. I'm not getting it to the fuel pump either! That's odd. Gravity should have pushed fuel to the bottom of the pump. I keep working my way upstream, trying to find the gas. It turns out, even the very first hose connection after the internal fuel tank is devoid of any actual gas. Hmmmmmmm.

Suddenly, inspiration! The vent cap on my fuel tank isn't properly allowing air to flow. So the fuel is vacuum-sealed in the tank and can't run down the hose! I take the fuel cap all the way off, and fuel starts streaming out the hose!

I'm once again on top of the world! It was a tricky one to spot, but I found the problem. This was probably the real reason I couldn't throttle up as well! When I asked for that much gas, it couldn't pull enough out of the tank because of the vacuum seal, so it stalled! I start putting all the hoses back on to really test my theory. I quietly chuckle to myself, thinking "it's a good thing cool heads prevailed. All I had to do was go slow and methodical, and not get frustrated. I'm such a genius and all-around capable guy!"

I go one by one on the fuel hoses. Each time I reconnect a hose, I open the fuel valve and ensure a little gas dribbles out the far end. I get back to the fuel pump. I hook that back up and give the cord a pull. A little gas comes out of the top of the pump, I'm in business! I hook the hose back onto the carb, the final connection!

I give her a good 5-10 pulls. It makes sense it wouldn't start immediately. The carb is dry and I have to work a little fuel into it first. But after 10 pulls, I'm still getting nothing. No cough, no nothing. Hmmmmm.

I unscrew the little drain in the bottom of the carb bowl. Nothing comes out. Curioser and Curioser! I know I'm pushing gas into the carb. But it's not making its way into the bowl.

I know! That damn float valve must not be working right. The carb isn't letting any fuel in! So the carb comes off once again. I have a real close look at that float valve, but it seems totally fine! But I'm struck by a clever idea. I put the carb back on the engine, but with the bottom half of it still taken apart. The float valve now hangs down in the open air, with no bowl underneath it to float it up. I put a little cup under to catch the gas, and open the fuel valve.

Boom! fuel dribbles out the float valve just like it's supposed to! I use my finger to "float" the valve closed, and the fuel stops just like it's supposed to! Now I'm really and truly confused. If the float valve is operating correctly, and I can get fuel to run out into the open air where the bowl normally is, why was the bowl empty when I unscrewed the plug?????? Maybe it was just a little stuck, and I have it freed up now?

I reassemble the whole thing and give it one more try. Still nothing. Still no fuel in the bowl on the carb! And that moment was the titular end of my wit. My wit could go no further. I had reached the extent of the reach that could be provided by my wit. And so I put a couple of questions to the infinite wisdom of the forum:

1. What the heck is happening here? Is the float not able to move freely in the bowl? It looks like it should, but I can't actually see in there when the bowl is on to know if the float is moving.

2. Is my hypothesis about the vent cap reasonable? Could that have been the main problem all along?

3. What does one do about a vent cap that doesn't let air in? I can run with the cap off, but not if there's spray or rain. Replace the cap altogether?

4. Back to the carb: is it even worth continuing to mess with it, or should I just buy a replacement carb? Anybody have a good source for one?

While I didn't try all the tricks you did, your experience sounds EXACTLY like mine... I mean to a T! Problem for me is I bought and installed a new fuel pump thinking that was the problem when maybe it wasn't. and then upon recent carb reattachment I broke the electronic choke module that my Yamaha has.... argh!


So I ordered a new outboard that may arrive around the same time we land humans on Mars.
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Old 10-05-2022, 14:02   #7
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Re: Wit's end with my outboard part 2

If you've had old fuel in any part of your outboard (and from your tale of woe I think you have) there will be a film of varnish-like fuel residue everywhere, especially round the carb and float pins. It all needs cleaning off...
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Old 10-05-2022, 14:40   #8
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Re: Wit's end with my outboard part 2

Quote:
Originally Posted by Noisykate View Post
If you've had old fuel in any part of your outboard (and from your tale of woe I think you have) there will be a film of varnish-like fuel residue everywhere, especially round the carb and float pins. It all needs cleaning off...
This - this right here is frequently the problem.
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Old 10-05-2022, 15:22   #9
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Re: Wit's end with my outboard part 2

My guess Woolf be that you had some contamination in the line that you found but when you reassembled the float needle valve something happened. It is real easy to put the little bracket in upside down. Also some of the brackets have little pincer like pieces that grasp the bottom of the needle valve. You can put the assembly back in without having those engaged. It all fits but the valve canít drop down enough to allow fuel in. Stay after it. Itís not rocket science and you have done good detective work so far. You are close. Fault has to be in that valve assembly. The fuel filter in-line just before the carb is an excellent idea. I like the clear ones with replaceable elements because I like being able to see that fuel is getting to carb. Good luck.
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Old 10-05-2022, 15:24   #10
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Re: Wit's end with my outboard part 2

If you are using USA gasoline from service stations, it will contain ethanol alcohol. The alcohol will corrode the internal passages of aluminum or magnesium parts.
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Old 10-05-2022, 15:58   #11
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Re: Wit's end with my outboard part 2

Jeb, thanks for the detailed followup. I could smell the gas as I read it...

Forums are great, but for problems like this it's hard to beat having a knowledgeable friend looking over your shoulder.

Re fuel vent - I can recall one spring launch... the boat slid sweetly off the trailer, squeeze the bulb, 5 hp outboard started second pull and sounded strong, and out I headed. And after about 10 min of motoring, the thing stutters and dies. Pulling and pulling... it won't catch. Yes, I forgot to open the vent on the gas tank. Crack that, it sounds like a big beer opening. Pump the bulb, engine starts first pull, problem solved.

#2 - I don't think the vent cap is the main problem, but if your cap isn't venting properly, yeah fix it or buy a new one. Running without a cap could be a fire hazard.

#4 - I'm the sort of person who, if I have the time, would try to find the problem and if possible fix the carb. It gives me that much more confidence to understand what went wrong and how to fix. But if your time and/or patience is limited, then sometimes you just have to replace a problem part, or pay someone to fix the engine.

PS I am a zealot for ethanol-free gas in small engines, and I have a semi-religious faith in occasionally adding a little SeaFoam to boat gas to help keep the fuel lines and carb clean.
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Old 10-05-2022, 17:59   #12
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Re: Wit's end with my outboard part 2

Quote:
Originally Posted by JebLostInSpace View Post
That actually makes a ton of sense! The hinge that comes out to allow access to that valve when I was cleaning was quite stuck and need a lot of force to move it. It's entirely possible I could have bent the little spring in the process. I guess I'll either get it bent back nicely so it runs, or buy a new carb.

Put a squeeze bulb on the fuel line.
Remove the carb, fuel bowl.
Invert the carb. And check the level of the float relative to the surface the carb bowl sealing flange, below it.
It should be about flush, or "level.
Turn the carb over and observe the float "drop".
There is a spec for this as well, but most importantly observe if the needle is dropping, or not.
Put the fuel line on the carb, and use the squeeze bulb to push fuel into the valve seat and needle. It should push easily.
Then lightly push up on the float and see if it holds with a light pressure, the squeeze bulb should get more firm as well.
This is a diagnosis of all but the pump.
If the pump is bad, you can use the squeeze bulb to supply fuel, temporarily.

And, if you want a new one here's a link...https://www.google.com/search?q=6+hp...&client=safari

Or.https://www.amazon.com/MagiDeal-Outb.../dp/B08VGVHJP8

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Old 10-05-2022, 18:08   #13
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Re: Wit's end with my outboard part 2

The nice thing about carrying a cheap new carb.....throw it on and see if she starts up. then you know it is your carb that is goofed up. You eliminate gas problems, ignition problems, and what ever....then when you get the time you buy a new replacement carb and tear the old and new down simultaneously and see what went askew.

My trimaran has a 10 hp efi (electronic fuel ignition....ditched the carb scene). But gas is important and i use stabilizer and seafoam.
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Old 10-05-2022, 18:24   #14
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Re: Wit's end with my outboard part 2

Is your fuel hose that grey hose with an interior usually black or blue liner? I have had this happen to me more than onece the interior liner seperates from the outer layer and sucks shut when throttle applied as well as many other situations. try changing fuel hose from tank to motor. getvrid of the grey china lamonated hose.
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Old 10-05-2022, 18:55   #15
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Re: Wit's end with my outboard part 2

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Originally Posted by JebLostInSpace View Post
That actually makes a ton of sense! The hinge that comes out to allow access to that valve when I was cleaning was quite stuck and need a lot of force to move it. It's entirely possible I could have bent the little spring in the process. I guess I'll either get it bent back nicely so it runs, or buy a new carb.

Sounds like you have messed up the float valve setting. It's easy to fix by bending the little metal tab to let the valve open when the float is below horizontal and close when it is level. You can look up the exact measurements and use a little gauge to set it exactly right but I've always just done it by eye.
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