wet plug and slight missfire at 3/4 throttle

Skeltonsc

Member
here is the suspect coil. the insulation crumbled off the wire so I smeared silicon onto it to try insulate it. the engine ran fine for a year like this, although it had a small miss and the bottom plug was wet.

this was the bottom coil which I have now put at the top.

I'm hoping the bottom plug will now be dry and the top one wet

Strangely though in the test tank it was missing quite badly and after swapping the coils the miss is still there but not as bad.
 

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Skeltonsc

Member
there is a small crack in the CDI around the mounting hole I dont think this could cause any issues?
 

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Skeltonsc

Member
here is the oil under the flywheel,

will try source the seals over winter yank the powerhead off again and repaint clean up etc.

I don't think this would cause the motor to bog down and run on one cylinder so its not critical at the moment
 

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MichaelK

Sealiner
I had 2x 40hp yamaha 3 cylinder 2 stroke outboard on my old boat. I also had a similar issue with my one motor. It would run fine for about 20 minutes then suddenly it would lose power completely and have a slight misfire, but still run.

It turned out to be the bottom carb. It was incorrectly set and kept flooding.The bottom carbs jets would also clog up everytime. After the mechanic made the necessary adjustments it ran like a dream.

I also found that when cleaning the carbs, water would be present in the carbs. So i placed an online water seperator which stopped that problem.
 

Skeltonsc

Member
Good day Guys,

Well I spend Friday fiddling with the motor and checking the coils etc with a multi meter and everything is in spec, I had the motor running in a test tank for 45 minutes and the electrical values didn't change at all.

funny thing is now with having the motor standing still I noticed what looks like a nipple sticking out of the block on the bottom of the intake this was dripping petrol probably about a teaspoon every 10 minutes or so. I would imagine that there should be a pipe connected to this nipple to drain out the bottom of the cowling???

Where can I get a carb kit for this motor I've called 3 different boat shops and dealers in the vaal triangle and not one gets back to me with a price.

The floats are both set level with the carb if I turn them upside down and don't seem to leak if I blow into the intake pipe.

The jetting is for the coast but this shouldn't be so much of an issue as the motor has been running fine for the last year +- 20 hours running

Oh yes the dam starter packed up while I was fiddling with it the brush carrier came apart in 3 pieces, had to build a new one out of fiberglass, glad it happened at home and not out in the middle of the dam, however the motor did start very easily with a rope around the flywheel.
 

MichaelK

Sealiner
If you have petrol leaking into your cowling, where is it leaking from? Fuel pump, carbs, fuel line, fuel filter????
You want to sort that out very quickly.
Also always rather replace damaged parts with new.
If dont have an auto lube and you mix your 2 stroke directly into your fuel and if its been standing a little to long, it clogs your jets irrespective of whether you are on the coast or not.
 

IWyk

Sealiner
MotorKing and Marine
012 335 2800
954 Steve Biko Street, Pretoria North

Waterworld
011 462 4390
234 Malibongwe Drive, Northriding, Randburg

Give them the Engine number and they can get the parts for you as they are the Johnson/Evinrude dealers.

As for compression test, it is always good to check that on older engines, good you have done that as it eliminates that issue.

A outboard needs 3 things to operate, Compression, fuel and spark!

Compression is sorted.

Wet plug is due to lack of spark or overfueling.

On some of the pictures, I see crimped connections, you may want to sort those out. Wires going to lugs and connected to bolts are earth wires and need to be clean and have a proper connection, some seem rusted.

Running fine when cold and then starting to act up after getting hot, indicates a overfueling problem rather than an electrical one. The motor can burn the excess fuel when cold(like a choke) but not once it heats up.

2 stroke carbs have to have fuel air mixing screw especially on a 1981 model.

You mention you have changed the coils around has the problem stayed on the bottom cylinder?
 

Skeltonsc

Member
Howzit guys,

Thank you for all the feedback,

I checked all the colis and electrics and according to the manual I'm well withen spec with regards to stator coils etc. only thing I couldnt check was spark gap with a plug tester.

So this leads me back to over fueling.

I will strip the carbs down again tomorrow and have a look

I will try set the float drop properly however there seems to be quite a large tolerance in the manual which states 1 1/8" to 1 5/8" which is a drop of 28,5 mm to 41mm which would mean the float can touch the bottom of the bowl.

as for the float level when the carb is inverted I've set mine level with the carb flange I cannot get an accurate measurement online but I have checked for pictures of the tool and will make my own assumption that its just under 3/4 of an inch if the image that I got is accurate I used the ruler in the picture to judge scale and superimposed it back onto the picture of the tool;)

I will double check everything this weekend and replace fuel lines clamps etc
 

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Skeltonsc

Member
here is the exploded view of my carb I really cannot find anywhere to set air fuel mixture
 

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honestly.... I think you are screwing around with the wrong stuff.

please see my earlier post.
swop carbs and plugs. see if the spark plug still changes to black!

that will give you a much better indication......if it is carbs or possible seal fault.

float levels don't change unless they have petrol inside of them.

screwing around with float level heights is cause of concern cause it will either over filling of chamber which causes over fuelling or causing your engine to run lean!!!
 

Skeltonsc

Member
Howzit Guys,

This weekend I fixed my started motor as when I repaired it last time I was unhappy with the insulation on the wires as I simply taped them up with insulation tape.

I bought some 6mm Fiberglass sleeving that the guys use on 3 phase motors and unsoldered the brushes and installed the sleeving this fiberglass sleeving won't melt and cause shorts like insulation tape will, if I had to crank the motor for an extended period of time.

I also replaced all the petrol hoses under the cowling as mine had gone rock hard esp the 6mm pipe from the pump to the carbs.

I also then double checked the carbs and moved the top one to the bottom and the bottom to the top. as well as cut new gaskets for the carb to intake manifold.

I polished the seats and needles and found the one float was slightly lower than the other one. now both are set at 19mm as per my vernier and exactly level with the carb flange.

Lastly I then cleaned and reseated all the electrical connections.

However the motor now idles perfectly and starts on the first turn of the starter. it also revs cleanly in the test tank.

Now I need to get out on the water to test

I really hope my gremlin has been put to bed.
 

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Skeltonsc

Member
Oh and before I forget, yes my carbs are still virgin carbs as the plug that covers the air screw is still in place.

I'm in two minds as to adjust these as the motor has been running fine for 36 years without adjustment so why should I fiddle with something that is probably not broken.

;)
 

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Skeltonsc

Member
During winter I think I'm going to redo the wiring harness on the outboard as its a bit of a patchquilt. the old wiring insulation is crumbling I cut this out a year ago but now other wires are crumbling thankfully not the CDI wires or the Stator wires :cool:

Will probably replace the whole connector and harness with molex plugs. as I don't think I will be able to reliably open the current connectors and replace the pins and install new wire.

wont be standard anymore but as long as its as good or better than the original 36year old plug I cannot go wrong.

What wire is recommended for longevity? with regards to heat oil etc. Normal automotive or the Silicone type?
 
Skeltonsc wrote:
Hi Guys I have an old Johnson 60hp 2 cylinder 2 stroke outboard motor, the motor runs and starts great however it has developed a small missfire at around 3/4 throttle and after long runs I find that the one plug is damp where the other is nice and dry.

what could possibly be the issue here? what do I need to check.

Thanx guys

your initial statement was above:
normally we tend to run away with treads and all sorts of explanations are given.

however it has developed a small missfire at around 3/4 throttle and after long runs I find that the one plug is damp where the other is nice and dry.


does the damp refer to water? or over fuelling?


again, just coming to one of your last posts.
running the engine in a tank full of water will most likely not show the problem as the motor is not under strain.

I do agree that the 2 x carbs floats needs to be the same height.

also notice...... running away here again but it is interesting.....

2 stroke engine needs to run a certain rpm at which the best scavenging occurs.
thus, allowing the most combusted solution out the exhaust ports and getting fresh mixture in to burn again.

it is noted that 2 stroke outboards do this at around 4000 rpm.

so, the miss fire you had, was it below this golden rpm number?

another aspect to keep notice of:
2 stroke carbs are normally jetted for sea level conditions.

thus down there the same motor will run much better then up here in the reef.
if a motor stays here then it should actually be jetted for 1600 meters above sea level.
it is to get the mixture at about 14:1.

1 last aspect, changing float level height will have 3 results.

1. float level too low, will cause a lean run on top end, wot. regardless of jets
2. float level too high, will result in a rich mixture on top end wot, regardless of jets.
3. float level right, will cause a 14:1 air to fuel ratio which will be the best combustion mixture which will create the best power.

cheers
 

Skeltonsc

Member
Hi Guy’s
 
All assistance is good wither it be  advise or criticism.
 
Let me try explain the boat and problem history that I’ve had.
 
I bought the boat last year March and after replacing the impeller,  crumbling wire harness then cleaning the carbs she ran well except for a slight misfire at around ¾ throttle, in the beginning I battled to get on the plane after fitting fins and a 15 pitch prop this problem was solved I get 37km/h top speed.
 
I used the boat illegally on the vaal dam up until November 2016 when I finally did my skippers and COF I estimate I did around 20 hours in this time with absolutely no reliability issues.
 
After doing the COF and Skippers etc I started using the boat on the Vaal river and also clocked up another good 15 hours in December.
 
Just after Christmas I went to Rus n bietjie on the vaal near Denysville and then my problems started.
 
I bent my skeg on a rock and after bending it straight launched again and could simply not get past the vaal dam wall before the motor would start missing and bog down so I would limp back to shore and clean the carbs check plugs and gap etc. I was convinced it’s a fuel issue because it felt like fuel starvation or a blocked jet.
 
This is when I realised the bottom plug was wet with fuel and much darker than the top one.
 
This got me to install new plugs and repair the thermostat as the motor was running very cold, she now runs around 78 degrees, I was hoping this would cure my wet plug problem as the fuel mixture was not warming up enough to atomise properly.
 
The thermostat didn’t cure the sudden loss of power though and also not the wet plug problem.
 
I have now done the following in order to the motor
 
1.       New lines and primer bulb
2.       Cleaned the fuel tank – it’s a plastic quicksilver tank which other than a few small black things floating around was never dirty.
3.       Checked and double checked the carburettor’s and cleaned with carb cleaner etc.
4.       New plugs and HT wires
5.       Replaced the gaskets under the powerhead as it was leaking dark oily marks down the outside of my outboard leg.
6.       I then took the boat out again and the problem was still there I simply could not do more than about 2km before having to turn around and limp to shore. That weekend I tried an electric fuel pump which didn’t make the problem any better or worse.
7.       I then repaired the leaky fuel pump
8.       Found a leaking crank seal
9.       This last weekend I cleaned the carbs again set them both exactly the same 19mm float (exactly level with the carb flange)
10.   I also swapped the coils and carbs top to bottom and bottom to top.
11.   Cleaned all electrical connections
12.   Repaired the starter motor
 
I’m hoping to go out on the water again in a week or two to test
 
Over winter I’m going to replace the crank seals and make up a completely new wiring harness and re-jet the motor for the altitude.
 
honestly.... I think. the impact damage to the skeg caused the lower crank seal to get damaged.

that impact caused a fault, clearly.

its only a opinion until it is cured it will only be opinions.
 

IWyk

Sealiner
A tip I can give you is, when storing the boat always run the carbs dry, this will prevent the twostroke in the carb from going tacky. When you hitch the boat up before traveling always pump the carbs full of petrol, this will prevent the needle and seat float from bouncing up and down in the carb bowl which can damage the seat or cause the float plate to bend which then makes the float level go out of setting.
 
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