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Old 23 June 2013, 15:23   #1
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Tohatsu running rough

Was out earlier today at Cruden Bay, and the engine (Tohatsu M60C) sounded like it was running on 2 cylinders. Carried on to our fishing spot a couple of miles out. I pulled the plugs. The top one was wet and oiled-up, the middle and bottom one were dry. There was also a tell-tale petrol film in the water - so I'm assuming its running rich and not igniting properly?

I cleaned the spark plugs. Still didn't sort it, so I renewed the top spark plug with a brand new one, and then fitted older sparks I had on board for the other two. Engine ran fine after that, but I get the feeling its still idling slow. On the tachometer it looks like 850rpm or so?

I service the engine myself, stripped the carbs a few weeks ago (no adjustment to idle screws), replaced impeller, gear oil, new thermostat and fuel pump gasket kit. Sparks were new at the start of the year. I also renewed the water/fuel separator filter in the console and fuel bowl on side of engine.

Heading back, after we idled a little near the Bullers of Buchan it felt bogged down again. Rather than pull the plugs we carried on, but full speed was down as before. The fuel primer seems okay, and goes hard when priming. Tank was vented too. Tried switching tanks - no difference.

Pulled the plugs at home, dried them off and it idled fine when on muffs. Fuel was new this weekend.

A few weeks ago the buzzer sounded. I assumed it was a possible low oil warning. It's an autolube, so rather than risking a seized engine, I added some 2-stroke oil to the fuel tank. Think it was possibly a overheat warning, as it was idling before the buzzer sounded (retrieving anchor). I replaced the thermostat with a genuine Tohatsu part and renewed the gasket. That fuel (with extra oil) will have already gone through the system, and there was no ill effects. Tell-tale is strong, and impeller was renewed earlier in year, so no concerns here.

I can strip the carbs, but think they need balanced? Any suggestions greatly appreciated.
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Old 24 June 2013, 14:00   #2
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Spartacus,

It's a waist of time and effort guessing by fingering parts to find the culprit. That symptom works mostly on engines which have been long time grounded without running fuel dry on carb bowl untill engine dies of fuel starvation, specially on 2 stroker engines. Fuel evaporates leaving 2 stroke oil residues that gums internal carb parts producing miss behaving performances when giving jnuice to engine.

You seem to be experimenting ignition coil internal issues on the one that's producing wet tip excess. Don't know how old is the engine, electric parts are not eternal, will fail with use and time. Buy a new small ignition coil and test...

If striping carbs, but don't play with fuel/air screws unless you have a multi wacuum tester to adjust all 3 carbs at same time, or a philarmonic ear to adjust carbs by ear..

Usually measure with a vernier tool the height of the upper screw tip with respect to base when engine is new & out of the box, That way will be adjusted as factory delivered in the event wanting to pull screw off to clean all carb related parts.

Happy Boating
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Old 26 June 2013, 01:28   #3
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Thanks Loco.

Engine is 2006 M60C 3 cylinder.

I agree about not messing with the fuel/air screws. It's been running fine, but the top cylinder plug is usually fouled. That one at least could be adjusted so it runs a little leaner - don't you think? I checked the engine before a couple of months ago (had sticking butterfly valve) and there is spark on all three plugs. Sure the HT leads could be possible culprit? The fuel air screw from lightly seated turned out by 1 + 1/2 turns? I'll establish its current position first.

In addition, I can up the rpm at little, as it feels slow at tick-over. I'll check the manual for idle speed (operating manual, not workshop manual) and adjust. As discussed - it controls all three carbs.
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Old 26 June 2013, 05:22   #4
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If you added oil to the fuel and there was still some dregs in the tank, it may be fitted with a rev limiter type arrnangement like my old Suz - when it hit "low" it rev limited, when it hit "empty it essentially pulled the deadman on you to prevent it siezing.


Other thought - (I had this at Easdale this year) - if you had the plufgs out are you absolutely sure al lthe HT leads are back on? I thought I had properly replaced mine, but the top wasn't quite pushed home and needed an extra heavy shove to get it to "click" into place.... I had had a concern they may be loose so had pulled them off to squeeze the terminal in a little on each cap. Bottom two had clicked back on - top (probably due to the angle / height etc as I stood behind the trailer) had gone on "solidly" but not quite clicked in properly electrically......
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Old 26 June 2013, 09:57   #5
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Spartacus,

It's normal to find one out of 3, 1 out of 2 more fouled plugs, think it's always the upper one which fouls more than lower ones. So all small Ignition Coils are working ok ? Sometime ago had a bit power loss on a 40C Tohatsu, the metal contact inside cap plug was found bit corroded, cleaned it, bettered performance just a bit, unscrewed the cap and found cable wire end being dark in color, cut 3 mm in lenght, wire color was completely shinny, screwed back cap, turn engine on, made all the difference.

Sometimes electrical hidden issues will give you trouble, specially the ones which are difficult to troubleshoot as in this case, same as when having issues with electrical components overheating when under load. Adjust main rpm screw, which controls all 3 carbs to at least 950/1000 rpm, 750 is bit low, could stall engine when engaging.

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Old 26 June 2013, 10:25   #6
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could it be the plug cap itself rather than the lead ,
on some of the rubber caps
ive had a couple where the metal spike inside hasent gone right through into the conductive wire part of the lead or its corroded/burned away or just come off inside even by just pulling plug cap off the plug thats caused a bad spark .
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Old 26 June 2013, 12:02   #7
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Quote:
Originally Posted by 9D280 View Post
If you added oil to the fuel and there was still some dregs in the tank, it may be fitted with a rev limiter type arrangement like my old Suz - when it hit "low" it rev limited, when it hit "empty it essentially pulled the deadman on you to prevent it siezing.
I confused what was probably a temperature sensor buzzer fault for low oil. It's an Autolube, so I added a glug of 2-stroke straight to the 25 litre tank. That was a couple of trips ago, so there has been fresh fuel through that fuel tank without oil. I topped up the Autolube tank on the engine - but never let it go anywhere near empty. I also replaced the water-pump impeller (start of the season) and thermostat (before the last trip out). I don't know if the M60C has a rev-limiter function or not?

Quote:
Other thought - (I had this at Easdale this year) - if you had the plugs out are you absolutely sure all the HT leads are back on? I thought I had properly replaced mine, but the top wasn't quite pushed home and needed an extra heavy shove to get it to "click" into place.... I had had a concern they may be loose so had pulled them off to squeeze the terminal in a little on each cap. Bottom two had clicked back on - top (probably due to the angle / height etc as I stood behind the trailer) had gone on "solidly" but not quite clicked in properly electrically......
Yes, definitely on, and tell-tale 'click' as the HT rubber insert connects with the spark-plug. However I will take a closer look at the coil/HT leads. They look fine, but I may need to replace that top one if problem persists.
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Old 26 June 2013, 12:08   #8
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Quote:
Originally Posted by Locozodiac View Post
Sometimes electrical hidden issues will give you trouble, specially the ones which are difficult to troubleshoot as in this case, same as when having issues with electrical components overheating when under load. Adjust main rpm screw, which controls all 3 carbs to at least 950/1000 rpm, 750 is bit low, could stall engine when engaging.
I will check out plugs. Haven't tested them yet.

I'll also up the rpm to 950 rpm (but leave fuel air mixture screw setting) and see how it feels. When I was running it on muffs after our last trip at the weekend, it was purring like a kitten at idle. Tell-tale was like a Clydesdale horse having a pee!
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Old 26 June 2013, 15:29   #9
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One thing is running engine on muffs, other on water. If adjusting rpm on muffs, surely engine will die once on water, need more rpm to compensate exhaust being near blocked under water rather than out of water when with muffs. It's better to adjust rpm once on water and well warmed engine.

When rpm is adjusted on water, propably will achieve slight more rpm readings when on testing/flushing on muffs, but that's ok. The times that have lowered rpm on muffs, engine has stalled once on water. 2 strokes horses are sometimes unpredictable running at low idle rpm.

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Old 27 June 2013, 03:39   #10
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+1 for loco's in water / on muffs.

As Mchappelow says, it doesn't take much wrong with an HT lead to kill a spark. Do you have a spark tester? Use it o mnthe lead and you might be surprised. Oprtion 2 is if you have or have friendly spark with as megger do an insulation test - your multimeter will say "insulated" but 1.5V DC might reckon it;s fine, but throw a couple of KV at high frequency at the leads and suddenly they donlt insulate so well.....

Same goes with the spark plugs - which is why they should be changed reasonably frequently.
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Old 27 June 2013, 17:58   #11
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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, 03:11   #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, 20:12   #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.

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Old 01 July 2013, 19:48   #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.

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Old 02 July 2013, 14:58   #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, 15:50   #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, 17:05   #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, 02:49   #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, 15:23   #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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