Another outboard problem!!!! grrr

O

ontheplane

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Hi all,

Was out on friends boat this weekend. The outboard was running ok, but seemed a bit down on power, struggling to get onto plane. Then it picked up and ran fine, on plane etc.

As we slowed down, and got near idle it cut out completely and wouldn't start.

Took the top off, and took out plugs, held them on a bit of unpainted metal and it looked like there wasn't a spark, fuel spots appeared in the water when pulling engine over so I don't think it's fuel.

Mate was accidentally holding the HT lead when I pulled it over once though and reported getting "a belt" from the lead, so there is some power there.

Changed plugs but still no spark.

Any ideas? Hope it's not something like the elec ignition module or something expensive.

Engine is a mid-80's Yamaha 15hp 2stroke

Thanks
 
Start by checking that you can get a good spark from each lead (without the plugs) do not know what to expect from a Yamaha but probably something like 7/16" good blue spark. (better still use a spark tester of course)

No spark from either then the ignition module is the most likely thing but really not something you can test other than by substitution.

Not cheap $123 in the US for a CDI Electronics one. Hope it turns out to be something cheaper. Your mate did get a belt so some hope.
 
How do I check the leads without the plugs in?

With new plugs I'm not getting a spark from EITHER plug.

Would a CDI unit go like that mid-run? And why was it fine on full throttle, but then no good as I slowed down?

Thanks
 
Could it be the ignition coil?? I didn't know it had one until I saw one on eBay!

Problem is I need to test these things before replacing them really, as it could get dammned expensive otherwise......

Anyone know how to test the coil & the CDI unit?

Thanks
 
As your mate got a belt, how about pulling it over IN THE DARK? Reason is you say it is a mid-80's motor so possibly HT lead insulation breakdown causing "tracking" in which case you should see little blue sparks wandering off in the dark. This will reduce sparking power available to the plugs. Do you have supressor caps - try changing those as well.

I'm with Vic on one thing, checking spark with a plug held against the head is notorious for not working, as you pull the motor over it moves, plug loses contact and you say to yourself "no spark" because it is human nature to always assume the worst. CLAMP the body of the plug to something metal on the engine when you test this way. Or as Vic suggests, a spark tester, dead cheap from here: http://www.trueshopping.co.uk/produ...n=Sealey_Sealey_In_Line_Ignition_Spark_Tester

Fuel spots in the water is not an indication you have fuel either. Were the plugs "wet" when you pulled them out? It is simple on the Yammies to whip off the carb, strip out jets, blow it out on an airline and put together and check that is not your problem. I have had exactly the same symptoms caused by carburettors with glop floating around in them and loss of power followed by a stop at idle and subsequent refusal to restart to me sounds more like carb problems than electrical and far, far more common.
 
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Plugs were very "wet" and I must admit, my "lack of spark" meant that was the area I was looking in.

I will take carb out and clean it through as I think that's a decent thing to do anyhow, however I will still persue the "spark" route first as I need to clarify that there is actually a spark - if there isn't I've found my fault for sure and if there is, then it's probably the carb.

I'll try the clamping it down thing, and will also try it in the dark (or at least under something to block out the bulk of the light. As you say, if there was nothing there my mate wouldn't have got a belt from it, he says it was bad, but then he's not used to being electrocuted so it may have only been a "half-belt" for all I know!
 
Dont know much about outboard engines, but if it has a faulty coil, this could lead to an intermittent fault. A break in the coil winding which opens when under load and hot, but is OK once it is not under load and cools. Experienced this a few times when I use to Rally.

One way to check integrity of HT leads with the motor running, is to ground one end of a jump lead to battery ground, then run the other end around and close to the HT lead, if there is a breakdown you should see the spark jump. Did this many times in the past to locate faulty HT leads, never did any damage to other components or batteries, I suppose the spark always goes to ground anyway!
 
ontheplane said:
With new plugs I'm not getting a spark from EITHER plug.
Click to expand...

How many ignition coils has the engine got? (I don't know the engine). If only one, then it sparks both plugs simultaneously, so both need to be grounded at the same time to see any sparks.

0.02p

Andy
 
Solved!

As many suggested, problem was crud in the carb.

Cleaned everything thru, all runs well now.

Thanks again to the clever peeps here on the forum.
 
Had a similar problem with a similar engine. turns out the fuel pump diaphragm was breaking up, as this is after the fuel filter all the crud went straight into the carb jets, on high revs the engine would run forever just sucking fuel out of the tank but as soon as you throttled down it died from fuel starvation then had to be re-primed via the bulb before it would go again. may be something to watch out for.
 
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