Outboard hassles

[brucehawsker]

Have a newish 4 stroke suzuki 6hp. 25 hours. Set it up on the driveway with a hose in the water inlet as per the manual. Started her up as normal. Water flowed fine. No problems with starting or running 1/4 throttle or more.

BUT - close to idle she runs ragged and stops. Checked fuel line, plug, all that. Runs sweet as anything at higher throttle. Changed the engine oil anyway...

But am concerned.

Could it be something to do with the fact that I am running it with the hose, rather than in the sea? Or do I have an idle speed problem or what?

Any ideas?

Anyone know who I can take it to near Aylesbury so I can get it sorted before going to IOW at end of week?

Any diagnostics I can try?

Thanks

Bruce

[Richard B]

OK, now I'm not saying you're being daft, but because you're in a different environment to when you usually run the engine (ie on the boat)...

did you open the air vent on the tank?

[brucehawsker]

I think I checked everything. But, just possibly it was not as open as I usually have it. Would that be sufficient to upset it at idle? Last time I used it was with an external tank. I have not used the internal tank for about three months.....

[Tim M]

If you havn't used the internal tank for a few months is there a chance the petrol's past it's best?

[brucehawsker]

No, fresh petrol today from local petrol station.

How do you diagnose these problems, generally? It all seems a bit of a black art!

Bruce

[Richard B]

I doubt that the petrol's that far past it's best (but hey, famous last words!)...

Diagnose problems like this by getting over the simple stuff first! And remember an engine needs fuel, air, water, a spark and oil (sump oil for 4-s, mixing oil for 2-s). Fuel and spark are the usual suspects.

Also, have you definitely switched to the correct tank?

[brucehawsker]

Yes, corrrect tank

Fuel line looks clear

Fuel visible in the tank. Correct tank selected.

Runs fine at higher revs

Spark plug taken out and carefully had a cloth pulled through the gap - no signifcant deposits

Ran brilliantly on external tank 2nd June

Not touched it since then. Came down in the car on its correct side. Then stood it up in garage. Ran water through it very briefly after journey down, but confess did not run it at idle as is it was cold so would not have noticed if there was an idle problem then.

Could it be that the oil, which was very black when I changed it, was the problem?

I have not run it since it kept cutting out at idle for fear of harming it. Changed the oil and then put it back in the garage without starting it.

Air intake looks fine. Stated normally so electrics likely to be ok.

Am still mystified.

If I am getting inadequate water throgh the hose (the cornnector does leak), could that explain the problem.

Tempted to set it up tomrrow in a bucket of water and try it again, having checked everything.

Otherwise, where could I take it to near Aylesbury? Any ideas

Thanks

Bruce

[Tim M]

Surely a lack of cooling water wouldn't cause it to idle roughly.....

[Richard B]

Originally Posted by brucehawsker

Tempted to set it up tomrrow in a bucket of water and try it again, having checked everything.

Go for it!

My suggestions now become more amateur as I don't have specific knowledge of your engine, but your logic sounds good. Start from the beginning and make sure everything's set up OK. I use a bin with water in to run my aux. at home - this would eliminate any water supply problems (I don't think they should affect it in that manner but overheating can cause strange symptoms AFAIK!

I don't know about outboard repairers up country - you may be better to take it to iow with you and find a repairer down there.

HTH!

[brucehawsker]

How much of the leg needs covering to run the motor in a bin of water to be safe?

Thx

Bruce

[Tim M]

Check to see where the water intake is. Just above the caitation plate should be fine.

[Richard B]

Well, just cover the water intake(s) really. But the water will froth up quite a bit (due to the exhaust) so allow a bit more - probably above the cavitation plate plus a bit more... and make sure the bin's not too full!!

I use the lower part of an old "swing-bin" (watch it, Garf!) and clamp the motor to a piece of timber secured in a vice. I'm in severe danger of a) tipping the bench over, and b) asphixiating myself in the shed - don't follow my example too closely!

[jwalker]

It's not going to be fuel starvation due to a tank breather.

Most carbs have a slow run system and a main system. With a small engine, it's likely that the main system comes into action fairly low down in the rev range. If only tick-over and slightly beyond is dodgy, then it's a fair bet the slow run system is at fault. I'm not quite sure about you description. Is the tickover lumpy and the progression fine or it the tickover fine and the progression lumpy?

Either way, a couple of quick fixes for you. Open the mixture screw fully or even remove it completely and put your finger against the hole to seal it. Start the engine, if you can get it to go. Even a reasonable blurp might do it. What you've actually done here is open up the slow run system on the down side of the jet and any small blockage will likely be sucked through. However, if the tickover is fine and the progression lumpy, this is not likely to work. Alternatively, you can try this since you are able to rev it; take off the air box, rev the engine then snap the throttle shut and immediately cover the intake to the carb with your hand. This will put the full depression of the engine onto the jets and it is a good way of removing a partial blockage.

However, if the carb has an idle jet and it is blocked by a relatively large particle on the float chamber side, the above may not be able to suck the debris through the jet. In this case, it'll be a carb off clean out job.

Since I'm not familiar with your particular engine, there is a caveat. Some tickover mixture adjustment screws adjust the air rather than the fuel. If this is the case, the above it less likely to work...but it might.

For completeness, if the the tickover is fine and fairly high speed is also fine, then it is likely a blockage at a progression hole. A progression hole is a small drilling in the carb which feeds some fuel as the throttle is opened. There may be more than one of them. As the throttle opening progresses, the main system comes into play and the tickover/progression system ceases to function. The hand over the carb technique will attempt to clear a progression problem.

I hope you can follow all this. It's a bit late for complex explanations plus, the whiskey doesn't help.

Good luck.

[timboli]

My experience is that most outbords run rougher when the exhaust isnt immersed,a dealer once told me that this is due to lack of back pressure,try it using a bin or in the water to see if that cures it!

[Cookee]

First thing I'd do would be to try it on the fuel tank that worked before - also was the fuel tank clean and dry before you filled it? Lastly just try taking the cap off the tank to make sure the breather isn't blocked in some way. All IMHO of course!

[Jono]

...throw it away and buy a new'n.....

[Bilge Rat]

Top advice there from Jono i see...just how did you get those two credability points ?

[brucehawsker]

Well, I followed advice and went out and bought the largest grey waste bin and carried it back to the office through the lunchtime pedestrian traffic on the hottest day of the year, of course meeting many friends who wondered what on earth I was up to!!

To prove it, please see attached!!!

OK. Well I tried everything. Thanks for the advice. The waste bin did not help!

Narrowed it down to two adjustments, both woefully poorly described in the Suzuki manual.

A. One is a sprung screw which is described as the tickover speed adjustment which actually moves the physical 'stop' on the throttle.

B. The other is a brass screw inside a silver nozzle which I assume adjusts the air / fuel mixture - it is a four stroke.

Adjusting either of these a little did not seem to make much difference. I eventually by trial and error seemed to get the smoothest runnning by having the brass screw (B.) about half way in - which I think was where it started off!!

However, I 'cured' the problem of the engine stalling at idle only by screwing the tickover speed adjustment (A.) almost fully in. Then the engine contined to run at idle. It seemed to run smoothly across all the range in neutral.

So how do I know how to adjust these two correctly when I put the boat on the water next week?

Did I have to adjust the tickover speed adjustment only because the engine was in a bucket rather than the sea?

Have I incorrectly changed the brass screw B.? How do I tell?

Am I going to cause myself a problem because I have tightened up A. almost as far as it will go?

Confused of Aylesbury

Bruce

[jwalker]

Bruce, if you can follow it, re-read what I told you last night. It's probable that by screwing the tickover adjustment right in that you now have the throttle plate uncovering the first progression hole and this will allow enough fuel to flow to run the engine. It appears you have a blockage at the mixture adjustment screw. Take it out, cover the hole with your thumb if possible, or some other thing but do not introduce any debris, and crank the engine.

It is very difficult to diagnose remotely, but from what you are describing, that's the way I'd be looking. Unless there's something you've not told me.
----------------------------------------------------
Readjusting after it's cleared. You have to start somewhere so what follows is just a general way of initially getting you into the right ball court, after that we can get the adjustment correct.

Presuming the blockage is cleared, screw the mixture screw right in until it is LIGHTLY seated. Take care with this, you don't want to flatten the seating. Unscrew it about 2½ - 3 full turns. Start the engine. Remember, you still have the tickover speed screw right in and it might rev furiously. If it does, stop the engine, readjust the tickover screw to about half adjustment and try again. Once you have it running adjust the mixture until it is running at its fastest. (If this is with the screw nearly out, you still have a blockage.) Back off or open up the tickover screw as necessary and readjust the mixture for max engine speed. You should be able to continue this double adjustment until the engine is ticking over securely and smoothly. When finally adjusting the mixture, you will get rough running >> good running>>rough running as the screw is unscrewed. If there is a slight uncertainly in the response err on the screwed out end of the adjustment. This is the rich end and it will help prevent a flat spot if you snap the throttle open.

All this should be done with the engine at correct working temperature but, as I said, you have to start somewhere. It may be worth doing it again after the engine has been running on the boat and it is frying hot. The mixture will likely need to be weeker (screwed in a touch). By this time you'll be an expert.

If the engine is not responding the way you'd expect from these adjustments then you'll have to look elsewhere for the problem.

[brucehawsker]

Do you mean take out the brass screw all together?