While out fishing the other day I took off from the ramp with my tinny and Yamaha 30CV outboard...
About 100 metres from the ramp I get this high pitch sort of ticking/pinging sound... then a few seconds later the motor starts missing and cutting out like its running on one cylinder... Anyway I quickly head for the closest shore and make it before it cuts out altogether... No paddling needed
After sinking 40cm into the mud on the shore I pull the cowl off and look around... Doesnt seem to be any external damage or anything loose etc...
So I pull the spark plugs just to check those.. Top one looks fine... Pull the bottom one off and WTF! The ground pin or whatever that bent bit on top is called has been bent right over and almost touching the central electrode thingy (excuse the technical terms). There was virtually a hair's gap between the two.. Aha! this has to be the problem (the symptons were logical for that problem), although I had never seen anything like it... I did perhaps have the plugs torqued up a little too much and perhaps they were extending into the clyinder too much, but even so they should have suitable clearance. I was using the correct plugs with gap set correctly as per specs... but this bottom plug gap was virtually closed.
So I crack open a set of two new plugs (NGK BR8HS-10) and put them in, carefully checking not to overtighten too much... Fire her up and she is back running at full power. Decided this was definately the problem and kept going and no trouble all day...
So, has anyone else had this happen before? I had never seen it and though it was quite odd!
Can't offer any suggestions as to what may have caused that to happen but they are the same plugs that the Merc/Mariner 30hp takes.I've had the plugs fail internally that make the motor fire intermittantly.Every thing looks fine on the outside and hard to trace until you replace the plugs and the motor runs as it should.Jim
Haines Signature "FinaLeigh" 580F 135 Optimax
CH 81 & 72 VHF
sorry mate she blew up, basic lean out or scored bore/coked ring lands trashed a ring on the exhaust port.Originally Posted by BaitThrower
While out fishing the other day I took off from the ramp with my tinny and Yamaha 30CV outboard...
About 100 metres from the ramp I get this high pitch sort of ticking/pinging sound... then a few seconds later the motor starts missing and cutting out like its running on one cylinder... Anyway I quickly head for the closest shore and make it before it cuts out altogether... No paddling needed
After sinking 40cm into the mud on the shore I pull the cowl off and look around... Doesnt seem to be any external damage or anything loose etc...
So I pull the spark plugs just to check those.. Top one looks fine... Pull the bottom one off and WTF! The ground pin or whatever that bent bit on top is called has been bent right over and almost touching the central electrode thingy (excuse the technical terms). There was virtually a hair's gap between the two.. Aha! this has to be the problem (the symptons were logical for that problem), although I had never seen anything like it... I did perhaps have the plugs torqued up a little too much and perhaps they were extending into the clyinder too much, but even so they should have suitable clearance. I was using the correct plugs with gap set correctly as per specs... but this bottom plug gap was virtually closed.
So I crack open a set of two new plugs (NGK BR8HS-10) and put them in, carefully checking not to overtighten too much... Fire her up and she is back running at full power. Decided this was definately the problem and kept going and no trouble all day...
So, has anyone else had this happen before? I had never seen it and though it was quite odd!
Oh, ok I just read the whole report, you may have spat a portion of a ring, otherwise i dunno strange things happen.
i would purchase a cheap compression tester from an auto store and see whats up, if nothing then forget about it unless simply interested and you pull the head you may find little dents...from that tinkle sound you heard...still the tinkle could have be pre combustion.
compression test.....
only a couple of things will cause that, if the motor is original and never been apart, then the things that can cause are not good things, first, a bearing has failed and the piston is able to come up a bit further and flatened the plug, or as mentioned, something has broken off a piston and when bouncing about (causing the funny noise in the process) and has hit the plug end and closed the gap, neither of these things is going to be fun or cheap, because the motor runs now, (without the noise) I would reckon that the piece of piston/ring is the culprit, and the offending bit has been burned to bits, or luckily shot out the exhaust, remove the bottom plug (the one that was closed up) and get a small torch and have a snoop inside to see if anything looks "bad" if you cannot see anything, then a head removal is in order, but do not continue to run the engine, you may turn an uncomfortable reapair bill into a new engine.
eeek ok thanks for the advice. I have a compression tester and will do a test and post results today. Will also peek into bottom cylinder and see if I can spot anything unusual.
If it was a bearing, wouldn't it have done the same to the new plug I installed after running it again all day?
yes, and also the noise would still be there, that's why I suggested the piece rattling around, mind you, it may have just been a small blockage causing it to run very lean, but you need to know, if the piston has a bit missing, or part of a ring has come off, it is only a matter of time before it just lets go altogether, a compression test MAY pick it up if the difference is big, but an inspection is a far better option if possible.
Ok I just took out the plugs (which were a new set with only an hour or so on them as per initial post) and they look ok... Normal tan colour on insulator and otherwise fine.
I shone a torch into each cylinder and I can't see anything abnormal... Each cylinder head does have a bit of carbon build-up on them however and are quite dark (its a 2002 model). But I couldn't see anything out of the ordinary and no bits cracked or loose etc (as far as I could see through the spark plug hole anyway).
I compression tested both cylinders are they both read pretty much identical at 120 PSI.
Thoughts?
There wa sno further noise that is for sure... I did notice the trip before when it was making that noise that I did have a bit of an air leak in the fuel hose fitting which may have caused it to not get as much fuel as it should have been... would that make any difference?
Otherwise see my post above with results of quick inspection and compression... Thanks for the ongoing advice too!
it might be your lucky day then, whether you remove the head to have a good look or not is your decision, it may have just been bad luck (or good luck) and you had a bit of crap block a jet and run it lean for a bit, but the choice is yours really, run it and hope, or remove the head and investigate, being a 2002 model, it might be time to remove the head anyway to check for salt build up and a proper inspection. Running lean may explain the noise, but not the plug being closed!!
Last edited by Noelm; 11-06-2010 at 10:44 AM. Reason: spelling
Yeah I will give it a bit of a run in the river next time where I am not far from any shore or the ramp and see how it goes. I rarely run the motor WOT so it doesn't get abused much
I might also run some Johnson/Evinrude Engine Tuner through it to clean up the pistons and hopefully the carby, or i'll investigate pulling th carby for a proper clean.
Will check for salt buildup too at some stage but no signs of engine overheating as yet or the like and the pump seems to work fine. I pulled and replaced the thermostat just as a standard sort of service item and when I did so, there was no sign of any salt build up or major corrosion in and around that part of the motor so I suspect the rest might be relatively clean too...
Anyway as mentioned, next trip I will take it easy and be on the lookout for problems and address as required.
It times like this is when a bore scope is handy.
Noel...do you reckon a big wod of carbon coming off the crown could have closed the spark plug gap??
Baitthower...was there an obvious mark on the leg of the spark plug where something hit it??
I intend on living for-ever....so far so good
The high pitched noise describes how a yammie I had once sounded when I didn't have the fuel line hooked up . the fuel pump really ticked loud .
I can't explain the plug though unless a piece of carbon came loose
Stuie
IF IT CAN'T EAT A WHOLE PILLY I DON'T WANT IT
Finga, No real obvious sign of a hit on the spark plug, just kind of bent down like the gap had been narrowed... same shape and same oritentation etc etc.
Stuie, Hmm ok, yes it is like a high pitch tick and it was consistent, i.e. like it would tick at fast but regular interval, but it would not stay ticking, just tick for a few seconds and then go away when I increased throttle, so maybe it is the fuel pump ticking?? And come to think of it, the speed of ticking seemed relative to the throttle too, so if I throttled up, it would tick faster, throttle down and the tick was slower...
Look closely at that plug again - could be a piece of the porcelian that cracked away and jammed for a minute in the bore. That would be a bad one and you may have got lucky and it got spat out the exhaust. After a can of engine tuner have a good look at the top of the piston with a decent penlight torch and if you see any indentations I'd keep a close eye on the compressions and a set of decent oars in the boat. Gaps can close and it usually hapens with rough installation of plgs where they get banged against the plughole on teh way in.
Silly but check it is the correct plug for the motor as different plugs have different reach.
Running lean with air being sucked in a fuel line can generate huge combustion chamber heat and teh edges of pistons can come off along with piston skirts.. A borescope may help see it it is the piston but there would be indentations in the rest of the piston where it did a little dance
You sure there was oil in the fuel and fuel was fresh?
Look at your butterflys in the carbies and see if there is any difference. Some brands still use a screw to hold on the butterfly and it wouldn't be the first to come undone and get sucked through the motor of jam in a crank bearing before getting spat out. Same for a peice of a reed valve - torch down carby to check if obvious and screws that hold reeds in place.
Check inside the cowl. Have had similar noises from cowl insulation rubbing on flywheel and also wiring loom etc not placed back where it should have been and rubing or blocking teh advance
The other cause which is common for the noise is the pull starter ( squeal) where it doesn't release properly , rubs etc. Have a good look at it as on other brands they can drop a circip and they then rest on teh flywheel . Not sure on a yami how they are connected. Warning that there is a spring in there that will take your finger off or a eye out so if looking be very carefull and gave a look at the parts diagrams first. Check tension on bolts that old down pull starter and if it has a electric start option check the gear is sliding up and down the input shaft cleanly and has all teeth while also springing back to where it should.
Unknown noises can bring tears to the eyes but go looking for the cheapest and easiest options before pulling stuff apart to narrow it down and going to a shop and have a engineer look at aborescope is a cheap option after that.
PS
With plugs out turn it over by hand and see if it is smooth , back and forward to see if there is any slap , chatter, flywheel side to side in case it is a crank bearing. It would have to be bad to discover it this way but easy quick check anyway.
Ps ya sure it was from the powerhead not the gearbox? Check the oil down there for smell ( burnt) and too many metal flakes or water in there.
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