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Old 27 June 2013, 18:58   #11
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Country: UK - Scotland
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Thanks 9D280. No, I don't have spark tester. I checked for a spark a few months ago when I had an issue with the butterfly valve seizing? I held the spark (touching the block) and got my wife to turn over the ignition. Fired on all cylinders. I replaced the sparks at the start of the season, but may replace them again to rule out any further issues.

Plan of action this weekend (brakes to do on the car too) is to strip carbs again, adjust timing, and replace sparks. Keep you posted.
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Old 28 June 2013, 04:11   #12
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Thing with that is there's visiual spark & there's enough spark to do something useful.....
I've had various engines have improved in performance just by changing the plugs - when meggered the insulation resistance of the old vs new plugs (at 1000V - a multimieter at 1.5V or so won't notice the dfference!) was substantial.


Spark tester is about as simple a tool as it gets. They look something like this:

http://images.monstermarketplace.com...79-235x300.jpg

When cranking you then open the gap until it stops sparking and there is a scale at calibrated in "good - dodgy - gubbed" kind of accuracy. It won't test the plugs, but does at least tell you whether the rest of the ignition system is providing enough juice to create a decent spark.
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Old 28 June 2013, 21:12   #13
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The nice thing about spark testers is you can vary ignition outing to ground distance to check spark's punch. Grounding plugs to engine will produce a spark, but not know if with sufficient strenght to sing a good Happy Birthday plug.

Happy Boating
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Old 01 July 2013, 20:48   #14
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Spartacus,

Before stripping carb down again, why don't you buy a new ignition coil and swap the one which is producing cylinder issues. I'm not a big fan about excessively fingering carbs, carbs are delicate, the least to mess with them, the better. Sometimes need to troubleshoot electrical parts, rather than mechanical ones.

Happy Boating
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Old 02 July 2013, 15:58   #15
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Quote:
Originally Posted by Locozodiac View Post
Spartacus,

Before stripping carb down again, why don't you buy a new ignition coil and swap the one which is producing cylinder issues. I'm not a big fan about excessively fingering carbs, carbs are delicate, the least to mess with them, the better. Sometimes need to troubleshoot electrical parts, rather than mechanical ones.

Happy Boating
Hi Loco, appreciate the suggestion. I haven't looked at the engine since last week. I picked up a set of new spark plugs (NGK BR8 HS10) the other day though.

I'm not even going to ask Tohatsu for cost of a new coil, as second hand the part is still 45. It's all money just now!
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Old 02 July 2013, 16:50   #16
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I think its same as the my 50 as far as fault finding ie 3 coils 3 carbs etc .
swap the coil with another one and see if the plug oils on that cylinder .
They hate extra oil and that will cause plug fouling for quite a while after as it sits in the bottom crank seal and gets thrown out when you least expect it but its always the lower 2 plugs not the top one that fouls on mine .
Do certainly mess with the air screws mine are now well over 2 turns open and it runs so much cleaner . start at where they are set now maybe 1.5 turns then then try it with a quater turn more and re set the tickover each time until if feels crisp and clean at lower revs , you will probably hear the tickover rise as you reach the best position .
Spend the cash on some iridium plugs they very rarely oil up and run nicer
presume you have drained the carbs and pumped some fuel through them , this higher ethanol fuel seems form a snotty lump in the carb if it gets a drip of water in it
Are the reeds ok could one be sticking open or broken . not sure if you can see them looking in the carb worth a look though . of course that all presumes you have good compression on the offending cyl
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Old 07 July 2013, 18:05   #17
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Thanks for all input over the last week or so. I replaced the sparks, and cleaned all the contacts on the HT leads, then adjusted the carb (two full turns out from lightly seated). Also removed air box and cleaned the carb intakes. Everything looked fine and dandy.

Engine ran without fault today until we were heading in when it died completely. Pulled the sparks, all dry. Checked the fuel bulb (hard) so I knew it was getting fuel. Tried switching over tanks, no success. Would turn over but die even with choke. I then noticed the fuel connector on the engine (Tohatsu female coupling) wasn't seated properly. Possibly a little corrosion caused it to seize up. Freed it up and connected the fuel supply properly then primed the fuel bulb. Engine started on the button. These Tohatsu stainless steel connectors are a pain compared to plastic Yammie connectors which are practically maintenance free.

Getting too old for this milarcy! live and learn though.

On a positive note, we caught the first mackerel of the season, and sea was flat calm.
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Old 08 July 2013, 03:49   #18
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It's good when you get to the bottom of something.......like a bottle of Malt!


Well done on the fish, ours arrived here last week, still just the joeys though, we will need to wait another 3/4 weeks before the bigger ones appear.
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Old 08 July 2013, 16:23   #19
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It's good when you get to the bottom of something.......like a bottle of Malt!
When the engine died, I tried the usual things, but remember a marine mechanic telling me not to keep turning the engine over as there is a real danger of burning the starter motor out. It's all a process of elimination. If the fuel hose connector hadn't resolved itself, I'd have looked to my back up 4hp auxilliary. Failing that, drop anchor and get on the VHF to the coastguard. Everything seems easier when the sea is calm and its 20 something degrees in summer sunshine.

I'm pretty sure the sparks and the adjustment to the top carb resolved the issue I had a couple of weeks earlier. All the sparks were dry when I pulled them, so pleased about that.

I had a couple of glasses of wine when I got back, prior to 2 hours of washing the boat down and putting gear away!

Quote:
Well done on the fish, ours arrived here last week, still just the joeys though, we will need to wait another 3/4 weeks before the bigger ones appear.
I put a lot of the smaller ones back. They're very resilient fish, when taken out to de-hook and returned to fight another day. My kinda fish. Had them BBQ'd tonight with Jersey Royal potatoes.
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