Biocide

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lexi

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I have an intermittant fault on Honda 8hp outboard. After trying everything the only thing I can think of is something lurking away in a hidden area of fuel system. Any tips for Biocide for Petrol.
Alex
 
Have done all that. Doused everything in carb cleaner etc. Checked foat valve and needle for wear and height. Mixture spot on. Removed all fuel to start with new stuff. Checked all coils with multimeter to Honda values. No exhaust leaks. Tappets are set correct. Still the same every year for last six years. Starts no problem and will run perfect for say 2 days then will cut out suddenly at any throttle opening but will start immediately and tick over. Put it in gear and it stalls. It will do this for either two or three times or ten times and sometimes more until it goes into forward and proceeds sometimes for two minutes or two days until it starts it again. Never failed to get me home. Putting it in reverse makes no difference and I can`t simulate it on a bench.
Alex
 
What about the actual fuel supply... is the area/tank well vented?

I seem to remember other posts advising that if it stalls it could either be fuel starvation or a blockage in the exhaust.

Just a thought.
 
Has done the same party trick with three different tanks all of which vent properly. I won`t sell it as I have two other engines anyway..........No cause without reason.
Alex
 
The blocked exhaust is worth thinking about. No corrosion as freshwater use only.A problem I`ve heard of on this engine is exhaust rot causing gas to build up under hood choking engine.I don`t have that and with hood off it acts the same anyway.
Alex
 
Sounds electrical to me. Could be the LT or HT side. Have a good look around the safety cut-out switch. Try shorting it out and see if that cures it.
 
That`s something I`ve looked at Lemain. Do you think it would tick over if switch was faulty. It checks with meter.
Alex
 
I've cleaned petrol fuel systems in the past with paint thinners (Xylene or similar) I don't leave it in for more than a few minutes and put petrol through straight away afterwards.
Please execute your own judgement before you do this.
 
Yes, it sounds as though you have an intermittent electrical fault - note that the problem happens at all throttle settings and happens instantly. That is not a usual symptom of fuel starvation. If you have fuel starvation, the engine revs tend to rise as the mixture weakens, then a short period of very rough running followed by the engine stopping. The problem could be in the HT or LT side - e.g. plug, plug lead and plug cap, coil, or the dc wiring to the ignition circuitry, which comes via the stop/emergency switch. If you can reproduce the problem reliably, try putting a 12V bulb across the ignition circuit and let it hang out of the case while running. Check to see if the bulb goes out when the engine stops.

HT fault finding is very hard...it's best to replace the plug, plug cap and lead especially on an older engine. Don't spray WD40 over it, it can work as a 'get you home' fix but tends, longer term, to cause more trouble than you started with. What you need on HT components is a nice clean dry surface.
 
Bulbs are ok as the three tanks that I use work fine on my other two engines. The pump on the block is ok. Stripped it and checked membrane spring etc.
Alex
 
Without meaning to sound rude, if you have stripped virtually everything apart to check, are you sure you are putting it all back together again properly?
 
Yes Lemain. Electrical fault has been my leaning too. It was a dealer friend of mine who thought that a microbe may be lurking some where in the system and it is a thought. I have a little Yam 4stroke which had intermittent fault similar to this although it either started or it didn`t........turned out to be faulty main coil replaced under warranty. There are exciter coils and main coils and it`s as if the first stage of coil is working when it ticks over but not the second when it`s stalling after being knocked into gear. The bulb thing is a good idea.....If you see a little fairy light in the distance you`ll know it`s me /forums/images/graemlins/grin.gif
Alex
 
No offence taken on the putting it back together thing. I always try to put it back better than it was in the first place.............which is easy when you`ve been messing around with Landrovers for a few years /forums/images/graemlins/grin.gif
Alex
 
my money is on the spark plug insulation breaking down - if you haven't changed it then I would certainly do so. If you have then I guess that gets ruled out. Symptoms matched those on my Honda Lawnmower exactly - and I went the same way initially stripping carbs tank etc etc /forums/images/graemlins/crazy.gif
 
Unlikely to be microbe if you have cleaned all the fuel system. Tends to take more than a few days to grow to problematic numbers (unless your fuel is coming from a dodgy source). I am assuming that there is no water in the tank also? Does the fuel look and smell normal? If it was microbes you would soon find the fuel filter gunked up and it would be unlikely that the fault would go away again.
 
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