Honda outboard motor

[lexi]

Seeing as we have such a universally talented and diverse bunch in here now I thought I would run my problem engine over y`all.

Honda BF8A outboard. twin cylinder 198cc ohc. 15 years old and way ahead of it`s time. Freshwater use only, treated like a baby and mint condition.

It will always start 3rd pull and troll slow all day or motor at two third throttle. At some point........be it within ten mins or ten hours it will die instantly under load. Sometime it runs for two days before it does it. On stalling , it will start first pull and idle perfectly. The carb is full. It will idle all day. Put it in gear forward or reverse and it stalls. Repeat this scenario 5 or 10 times and she pulls away as normal............only to do it again 5mins or 5hrs or two days later. The most it ever goes faultlessly is two days roughly. Will let everyone know when I get it sorted and what it was. Meanwhile give me your thoughts.

Alex

 

[Rusty]

Breaking down under load is a symptom of the HT breaking down, spark plug, plug lead, or coil.

 

[lexi]

Thanks Rusty
Stripped of insulation on Ht leads as you cant renew them.........all good. Managed to thread insulation back on the doubled over leads with two layers of heat shrink.

That made no difference. Checked the resistance of coil which was ok but decided to swop coil and two attatched HT leads for a S/H replacement.....exact same result as before.

The other s/h coil/leads could have the same fault but it would be a bit of a coincidence.

Have started and run motor in pitch dark.......no tiny blue sparks.

Alex

 

[rusty69bus]

check the carb, and that theres a proper nice big spark it could be the power going t the coil?

 

[lexi]

Have cleaned carb once.........I am doing it again. Have not found anything suspect in carb. Have examined float needle and put a very fine copper wire through all jets and they seeem clear. It is soaking in carb cleaner now. spark could be weakening as it cuts out but it always has enough to start it.

Alex

 

[Drains]

Sounds like a piece of dirt with comic timing getting into a jet (not the idling jet). Or a hair or something strange like that. I hate petrol engines!

 

[lexi]

I`ve had the hair thing before Si. The little Yamaha two strokes with integral tank used to save them up in the main jet. They came off the wooly jumper as you filled up tank. The result was a more spluttery end than this... which is instant.

Alex

 

[rusty69bus]

pull the completely to bits to clean take out the jets if they come out and the emultion tubes if any






all i know is you'll proberly kick yourself when you find the problem.

 

[malcolm]

Been trying to decide if the carb would fill if there was a vacuum inside a tank. You've checked the breather in the tank?
Does sound like fuel if it starts but doesn't pull away, but works other times.

 

[lexi]

pull the completely to bits to clean take out the jets if they come out and the emultion tubes if any






all i know is you'll proberly kick yourself when you find the problem.

Yeah It`ll be ......." You`ll never guess what I found". Yeah Malcom have pressurised tank and primer bulb then sprayed with soapy water.....they all hold with no leaks. Air vent working. Have tried 3 different tanks and lines with same results. Checked every line inside engine with compressed air. The symptom is very much like if you take off with air vent closed. In fifteen mins you will come to a sudden halt as you realise you aint opened air vent.

This avenue may be Red Herring though as it will act up even with remote tank disconnected. Thought it may have been exhaust leak choking engine but it does the same when engine hood is removed.

Will blow out carb again today and put it back. Problem is I cannot replicate the fault. Have checked continuity of every wire and resistance values of all components. Also wiggled everything while under power (not a pretty sight!).

Alex

 

[lexi]

Have soaked metal carb parts in cleaner overnight. Blew everything out . Checked thermostat...perfect. Put all back together and started and ran in drum. Will try it out on the water this week. If it fails again I am now leaning towards CDI unit. Priced one today at 195 quid....ouch. What do guys think? A capacitor in the unit may be failing intermittently. There is no way to test this as it`s sealed. Pulser coil.. Exciter coil and ignition coil all feed in and out of this large matchbox. If a capicitor wasn`t triggering would engine always start and tick over yet fail on load? Next move is to try and borrow or pick up one up from a breaker.

Alex

 

[shenion]

Could be CDI unit. I'd suspect the pickup coil.

Does it have a low oil cutout? If so maybe the sensor is bad (or it is low on oil ).

 

[lexi]

Pick up coil resistance value checks out. No oil cut out. When engine cuts out under load I know that it is going to start again. It is only going to fail when I load it into gear. Wonder if all the values are normal when it is ticking over at that point. Just wonder if when it stalls anything can be measured.

Alex

 

[irondarren]

What fuel you running it on lexi unleaded? daft question is it four stroke or two stroke. Just had an off the wall thought which i have known to happen with older briggs and stratton four stroke engines. The valves ie inlet, exhaust can stick due to the fact it was ment to run on leaded petrol, therefore there is no lubricant on the valves and they stick and the engine dies, as i say its an off the wall thought. If the engine is four stroke next fuel fill add a little two stroke oil. Ive got an old brigs ride on lawn mover which i splash a dash of oil in with every fuel fill.

 

[lexi]

Thanks Darren
Unleaded fuel. Hondas are all four stroke and designed to run on it as compression ratios are low and they have hardened valve seats. Will keep it in mind mate as I aint ruling anything out.

Alex

 

[irondarren]

must admit lexi i hate problems like this, it breaks down when it feels like, restarts straitaway. Doesnt give you much to go on. best of luck with it

 

[Drains]

Here's one, probably not your problem but has similarities.

Years ago a mates Golf wouldn't accelerate without choke. Various garages said the carb was u.s., needed a new one etc.
I had a peek. It was the accelerating jet that was blocked. Couldn't clear it so I removed it . Never missed a beat after that!

Your carb probably has a butterfly valve for increased mixture on acceleration, but hey, just a thought.

 

[lexi]

Went over that carb today Si. It was so clean it was a pity to put it back in engine. Will take it out on water and test. If problem arises as usual I will discount carb for the moment.

Have run a Biocide through fuel system in case bacteria was lurking somewhere. Was wondering that if spark was weak enough at a certain time to stall under load...but start immediatley.could that not be detected somehow at that moment. What about connecting voltmeter or timing light to spark plugs while running. Take the reading when running hard , then when it stalls start it again and watch reading. I know when i put that lever into forward it is gonna stall. Does anyone think this may tell me anything.

The other thing I mentioned about starting engine in the dark and watching for the tiny blue sparks of HT breakdown. Well yes I did this..........but not under load. May try that.

Alex

 

[Drains]

I know when i put that lever into forward it is gonna stall. Does anyone think this may tell me anything.

You gotta stop them negative waves Moriarty - too much negative waves..

Si

 

[Drains]

Alex, I have had this exact same problem a couple of times - on cars, a long time ago, and I can't for the life of me remember what caused it. Though I'd plump for a crappy condenser, off the top of my head. Sorry pal. Can't help.