4 stroke outboard chokes

[bamspm]

Is it normal for small 4 stroke outboards to race at virtually 1/2 throttle when the choke is pulled out? I have now had 3 small outboards 2.5 to 5hp Mariner, Mercury and Suzuki and they all do this, even straight from the manufacturer. I know that the revs need to increase a little when the choke is pulled out but mine does seem excessive. Is it reasonable and practical to adjust it?

 

[ShipsWoofy]

I am not overly pleased with my new suzuki 2.5 4st as even on a hot day I need to use the choke to start it (from cold) and it will stall if I let the choke off too quickly until it is up to temp.

I don't know if it is a fault or the idle is set too low or I am expecting too much from a single cyl 4st engine. Opening the throttle a tad during starting is all a motor should need, not a bit of throttle and full choke. I am thinking of taking it to a service centre to see what they think before I try adjusting it. I am not sure if Suzuki will look at it as a warranty complaint, will tell you if they do.

Your post though, makes me think these little engines are possibly just a bit quirky and we may be expecting too much from them?

 

[Lakesailor]

I think most 4 strokes are a bit tempremental about cold running. The amount of choke to start and the time you leave the choke on seem to be very important.
It could be because the mixture has to remain vapourised during the induction and compression stroke in a cold cylinder before firing, whereas a 2 stroke has a lot more charge movement prior to the spark and this helps to keep the charge a vapour.
Just a thought.

 

[misterg]

[ QUOTE ]
I am not overly pleased with my new suzuki 2.5 4st as even on a hot day I need to use the choke to start it (from cold) and it will stall if I let the choke off too quickly until it is up to temp.

[/ QUOTE ]

I don't know the engine in question, but on every Japanese motorbike I've had it's been the same: 3/4 choke, no matter what the weather. The only difference is how quickly you can knock it off. My Mariner 2.5 2 stroke is the same, too. Maybe the mixture is more tightly controlled on modern engines (due to emissions limits, etc.)??

FWIW, I wouldn't class this behaviour as a 'fault', but your opinion may differ /forums/images/graemlins/grin.gif

Andy

 

[billskip]

IMHO If the settings are adjusted you will proberbly find the engine performance will also alter when it is at running temp.

It is possible that there is an air filter that needs cleaning and the designed volume of air required on cold start is also being restricted. the butterfly choke plate has a small hole in it to allow the correct volume of air for cold start..if the air filter is also blocked it will give even less air on cold start and possibly increase the revs.

AS said all IMHO

 

[ShipsWoofy]

[ QUOTE ]
FWIW, I wouldn't class this behaviour as a 'fault', but your opinion may differ

[/ QUOTE ]

I wan not happy, but after this thread have satisfied myself that this is the norm. I have only ever had 2st in this size range previously and the starting was far simpler, you could knock the choke off almost immediately even in winter once running.

Thing is, I just did not want to go back to mixing oil, leaving a film of oil around the dinghy whenever stopped and having to drive home with the windows open to dissipate the petrol/oil smell. The 4st when running is so much quieter and the problems of storage etc are not so bad for us on a catamaran.

Sorry to hijack the thread a bit.

 

[philfin]

Coincidentally, though not sure entirely related, my 4st Johanson 4hp has started doing something strange. As mentioned previously, It always needs choke to start whatever the weather but start it does first pull. Can usually then knock the choke off quite quickly and away we go.

Now however, it still starts fine but wont run off the chioke at less than half revs and below this it just dies. All seems a bit odd. Motor is only 2 years old and has never been used much. I've had the carb apart and nothing seems wrong, no dirt or things not moving as they should. I guess the petrol is a bit old now, would that make any difference? The spark plug looks a bit sooty but I figure its because of the constant starting and stopping whilst trying to figure it out. Perhaps the plug has had it? I will put a new one next to see but could any of you point me in the right direction please

Thanks

 

[bamspm]

They are very interesting comments. I don't have any problem with the running and performance of the engine it is just that it needs full choke to start and as soon as it starts it runs at what sounds like full revs until the choke is pushed in. Fortunately the choke can be pushed in fairly quickly but by then the whole marina is probably awake!

 

[Lakesailor]

If your motor will only run on choke there is a blockage of some kind. If it has a slow running jet that is favourite or if the fuel level in the float chamber is low that would affect slow running. Sometimes some water in the fuel can have the effect of partially blocking a jet.
Clean the carb out.
The sootiness will be through using the choke control too much.
I'd try a clean plug after cleaning the carb as the sooty one may mask better running.

 

[Boathook]

I had this on a 2 stroke a few years back. The idle jet in the carb was blocked. Had to strip the carb down and spend ages trying to clean a very small hole - without damaging it. Even if the jet looks clear any muck alters it!

 

[Goldie]

My starting procedure for the Suzuki 2.5 is: Full Choke and throttle all the way closed. So far (2 weeks!) it has never failed to start first pull. The choke can almost immediately be pushed in half way and all the way in after a couple of minutes.

 

[ShipsWoofy]

[ QUOTE ]
My starting procedure for the Suzuki 2.5 is: Full Choke and throttle all the way closed. So far (2 weeks!) it has never failed to start first pull. The choke can almost immediately be pushed in half way and all the way in after a couple of minutes.

[/ QUOTE ]

I have found it easier to start if the throttle is on the start mark, I guess 1/8 open. No doubt it will start fully closed, this is always after much messing trying not to use the choke. I will now just add choke and start without throttle.

Have you noticed occasionally that you hit a compression stroke that will pull the engine up off the transom if it is on the wrong part of the pull? That is a little annoying too!

 

[m1taylor]

I have heard that in order to get through the EU emmissions regulations small engines are adjusted to the extreme - don't know if that's true or not. You'll all hate me for saying this - just got a seagull as a spare off ebay - fresh fuel, flooded carb, started second pull, choke straight in, ran like a dream. Does the new smoking ban apply to seagulls??

 

[Goldie]

I've been out to the boat again this evening and tried with no choke. With the throttle all the way closed, it started first pull and settled straight to idle. As for the compression, try pulling gently until you feel the compression go over (and no more), let the starter recoil and then give one sharp pull to the full extent. Touch wood, it's worked evry time so far (and I might regret saying that /forums/images/graemlins/tongue.gif Good luck.