[christian.hess]

The screw in the side of the carb is the idle speed adjustment. It's not a nozzle or anything but it's like a stopper for the whole carb assembly that sets the lower bound of the throttle. Besides doing that, shouldn't have any other effect on performance.

I don't know how many turns it is, I just adjusted it until I liked the idle speed. Before adjusting it was a bit too fast.

No, please keep "bugging" me.

So I moved the clip from richer to leaner (notch 3 to notch 2). Per the service manual notch 2 is the factory standard. The manual said a classic case of too rich was losing power at 2/3 throttle, and since my engine seemed to be doing that, I moved the clip (this was before my current problem).

So it always starts first pull after stalling which makes it seem like it isn't flooding.

thats what I was commenting on...usually you get a fumbling gurgling sound when the engine is running to reach and very hard to attain if not impossible to attain full throttle

in BOLD that is often called a fuel screw, thats what I was saying...you must know what its set at...you will not idle well and it might be the big cause of trouble...

also your manual shold state how many turns for "normal" sea conditions...again as a starting point.

for your info fuel screws on 2 strokes carbs often richen up the mixture(more fuel per air particles) when turning the screw IN

on most 4 strokes the fuel screw or idle enrichment screw the opposite is true...OUT means more fuel.

so make sure by all means you count how many turns out you are

report back

I don't see any signs of head gasket leaks. No residue on the outside or anything. It looks fine.

thats what I was commenting on...usually you get a fumbling gurgling sound when the engine is running to rich and very hard to attain if not impossible to attain full throttle

thats why in gear its loaded more and when not in gear or neutral you can acheive full throttle

in BOLD that is often called a fuel screw, thats what I was saying...you must know what its set at...you will not idle well and it might be the big cause of trouble...

also your manual shold state how many turns for "normal" sea conditions...again as a starting point.

for your info fuel screws on 2 strokes carbs often richen up the mixture(more fuel per air particles) when turning the screw IN

on most 4 strokes the fuel screw or idle enrichment screw the opposite is true...OUT means more fuel.

so make sure by all means you count how many turns out you are

report back

I would put a new plug in after adjusting the idle speed adjustment and see if you see any improvement

if none of this improves(even leaning it out more on the needle) look at your plug cap, if it has a resistor and the condition of your coil

the shop manual should have the resistances the coil has

 

[asdf38]

thats what I was commenting on...usually you get a fumbling gurgling sound when the engine is running to rich and very hard to attain if not impossible to attain full throttle

thats why in gear its loaded more and when not in gear or neutral you can acheive full throttle

in BOLD that is often called a fuel screw, thats what I was saying...you must know what its set at...you will not idle well and it might be the big cause of trouble...

also your manual shold state how many turns for "normal" sea conditions...again as a starting point.

for your info fuel screws on 2 strokes carbs often richen up the mixture(more fuel per air particles) when turning the screw IN

on most 4 strokes the fuel screw or idle enrichment screw the opposite is true...OUT means more fuel.

so make sure by all means you count how many turns out you are

report back

I would put a new plug in after adjusting the idle speed adjustment and see if you see any improvement

if none of this improves(even leaning it out more on the needle) look at your plug cap, if it has a resistor and the condition of your coil

the shop manual should have the resistances the coil has

Christian, I'm pretty sure the screw on the side has nothing to do with rich or lean. It simply sets a lower limit on the throttle by preventing the carb from closing beyond a certain point. So screwing it in or out is identical in effect to moving the throttle lever up or down.

But, I solved my problem at least for the moment: I bought a new engine. A tohatsu version of this same engine.

The good thing here is that when I have time, I'll be able to swap parts between them (especially the carb) which will be great for isolating the problem.

I'll be sure to post back results when I get around to it. Eventually I'll get both engines working and sell one.

 

[christian.hess]

well thats good, so your carb has no fuel screw or lean rich adjustment anywhere?

I have an evinrude 3.3 and it has the exact same screw, probably same carb its spirng loaded its not a throttle arm stopper set screw but indeed a idle adjustment screw

parts #22 and #23 on your carb diagram

on many parts fiches they are simply called screws...I dont see a throttle arm stopper like you are talking about at least on my carb

from the looks if it these carbs are the exact same...

 

[Boredop]

Tank vent.

 

[capecodda]

I have one of these clockwork yoyos and the symptoms you give are something I have experienced.

Fixed it by ensuring that the whole fuel system was clean. Starting with fuel line from the tank through the fuel switch to the bowl and through the main jet.

There is a secondary jet controlled by the screw with the spring on the side of the carb. Critical if you want a good idle.

Mine has displayed the symptoms you list after getting bad fuel but cleaning the fuel system has always restored normal service. I would go through your fuel system again and make sure you are not feeding it fuel with water in it.

Tohatsu 3.3 with N/F built 2006.

Have you thrown away all the old gas, started with a clean gas tank and supply hose, then re-clean the carb with carb cleaner, leave the cap off the gas tank you know it's venting...and then does it still happen.

I've had similar experiences, not tossed the fuel, and it keeps reoccurring till you do.

 

[asdf38]

Well a year later I finally got back to this engine.

So I convinced myself running in the bucket that the engine was better after removing and reinstalling the carb more tightly (it attaches almost like a hose clamp, but also needs to be pressed in against a gasket).

Anyway I was wrong and the old behavior of dying in gear with any throttle was still there. It reved fine in neutral, but just a small increase in throttle while in gear killed it.

Finally I figured out the procedure:
Try multiple times to simultaneously add choke and throttle to get it from idle to 30% throttle without stalling. Somehwere around 50% choke is the right spot to do this (but no it won't run at this choke at idle). If you can get past the dreaded 20% throttle point it's better and usually won't stall as long as you keep the choke somewhere between 30% and 60%. As the throttle increases past 50% the choke needs to be carefully decreased. This is fairly easy to adjust because at least it doesn't stall. You increase throttle and then tweak the choke for maximal revs at that point.

By the end of this procedure I had the engine running better than ever and got my little 9ft inflatable on plane, barely, with me lying in the front for low air resistance and steering by shifting weight on my flat local lake (7.8 knots)


Anyway, does any of that shed light on the problem? It's obviously the carb given the sensitivity to the choke but I've taken out and cleaned/inspected the carb like 8 times. And the carb is literally brand new (I have the paperwork for the carb replacement from shortly before I bought the engine).

Edit: Ok I went back and read the thread again. Someone asked whether it would run with the choke. The answer is yes but the problem was the difficulty of getting it through 15-25% throttle without stalling. It seems particularly sensitive at this point.

Also lots of people were asking whether it was too rich or too lean. Ok now I know it was too lean (because it runs with choke) but it doesn't seem normal how sensitive it is to the choke. Tiny adjustments make all the difference and different amount of choke are needed at different throttle levels. And this engine doesn't even have an adjustment for rich/lean externally on the carb.

Seeing how I went and bought a second identical engine, I now have experience and that engine had none of these problems.

Anyway if people have more suggestions, great, but I'm reasonably pleased that at least I know how to get the engine to run.

 

[chrisbink]

Well a year later I finally got back to this engine.

So I convinced myself running in the bucket that the engine was better after removing and reinstalling the carb more tightly (it attaches almost like a hose clamp, but also needs to be pressed in against a gasket).

Anyway I was wrong and the old behavior of dying in gear with any throttle was still there. It reved fine in neutral, but just a small increase in throttle while in gear killed it.

Finally I figured out the procedure:
Try multiple times to simultaneously add choke and throttle to get it from idle to 30% throttle without stalling. Somehwere around 50% choke is the right spot to do this (but no it won't run at this choke at idle). If you can get past the dreaded 20% throttle point it's better and usually won't stall as long as you keep the choke somewhere between 30% and 60%. As the throttle increases past 50% the choke needs to be carefully decreased. This is fairly easy to adjust because at least it doesn't stall. You increase throttle and then tweak the choke for maximal revs at that point.

By the end of this procedure I had the engine running better than ever and got my little 9ft inflatable on plane, barely, with me lying in the front for low air resistance and steering by shifting weight on my flat local lake (7.8 knots)

Anyway, does any of that shed light on the problem? It's obviously the carb given the sensitivity to the choke but I've taken out and cleaned/inspected the carb like 8 times. And the carb is literally brand new (I have the paperwork for the carb replacement from shortly before I bought the engine).

Edit: Ok I went back and read the thread again. Someone asked whether it would run with the choke. The answer is yes but the problem was the difficulty of getting it through 15-25% throttle without stalling. It seems particularly sensitive at this point.

Also lots of people were asking whether it was too rich or too lean. Ok now I know it was too lean (because it runs with choke) but it doesn't seem normal how sensitive it is to the choke. Tiny adjustments make all the difference and different amount of choke are needed at different throttle levels. And this engine doesn't even have an adjustment for rich/lean externally on the carb.

Seeing how I went and bought a second identical engine, I now have experience and that engine had none of these problems.

Anyway if people have more suggestions, great, but I'm reasonably pleased that at least I know how to get the engine to run.

Did you ever find the problem? I have the same issue.

 

[SeanM26]

Just read this whole thread. It really does sound like the low speed air/fuel is out of sorts. I've seen the low speed needle get bent during a rebuild that caused it to lean out right off idle and die. The engine would run ok once it started pulling fuel from the main jet.

Another issue I have seen is people reroute the fuel supply to add a filter. They run the line too close to something that gets hot and ends up vaporizing the fuel in the line causing the engine to stall at anything above idle.

Just a couple thoughts.

 

[chrisbink]

Thanks.
I think there is only one jet on the Mariner 3.3 and I don't think it is damaged. I have exactly the same issue being able to 'nurse' the throttle to around 2/3 open without dieing by tweaking the choke as I go, but not ideal. Im quite confident it's lean mix issue I just need to work out what is causing it!

 

[capta]

As this is a ghost thread from June 2014, I rather imagine that he's either got it running or more likely, disposed of it some years ago. lol

 

[SeanM26]

As this is a ghost thread from June 2014, I rather imagine that he's either got it running or more likely, disposed of it some years ago. lol

Chrisbink posted this morning that he was having the same issue.

 

[asdf38]

Heh Nope! It's still in the same condition but I've gotten better at manipulating the choke.

I also still have no confidence in its cooling since it only just dribbles water out the hole. And gets super hot to the touch (though I've been meaning to research whether this is normal or not).

And actually its more relevant than ever because as of last year I downsized from the Contessa to a Precision 18 and it's my engine for the precision. Luckily I almost never motor and am in well protected waters....

 

[chrisbink]

Yes, maybe I have it now!!!

 

[Gs425]

So I've read this from here in uk and I have found a similar issue but eventually worked out what it was caused by. On my small tender the motor would die at higher power setting but would start again first pull.
What was causing this was the 2.4m tender would push the bow up, and with my weight in the back it meant fuel was trying to flow up hill because the tank is at the rear !!! This was therefore causing lean mixture symptoms up until the point of actually stopping fuel getting to the carb. A full tank helps. Balancing the dinghy helps. Stepping the tilt adjust up a notch or two helps.
Trust me....I was fooled too until it dawned on me, especially because these tohatsu based engines are otherwise bullet proof Cheers