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Yachtwin 3HP will not run

S

SKIDDERWOLF

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Hi all, I have a Yachtwin 3hp which I can not get running. Its new to me and Its a 1967 model all turns freely and has compression. Good spark from both plugs.
Carb has been cleaned and rebuilt using a new kit.
I can only get it to fire for very brief periods 2-3 seconds before dying. If i move the speed lever left to slow position I will either get a backfire or nothing and moving it away from the run position will sometimes cause a cough but then nothing more. I have tried turning the mixture screw out 1.5 turns as stated to a base start figure and have gone both riched and leaner than this but no good. If I pull the plugs they are wet so fuel is getting there but im stumped as to what could be wrong. I have not touched the engine yet. I am thinking there may be a bigger fault with this motor.
Any ideas folks?

Rich
 
I say you do not have spark !-----Laying the plugs on the block is a waste of time.----Good spark is considered to be able to jump a gap of 1/4" ( 6 mm ) or more.---So test and report what you find.
 
Use something that will force that wonderful magneto to jump a gap of 1/4" or more.----Glue some wires with 1/4" spacing on a piece of carboard is one simple way.-----All the coils cracked on 1967 models and should have been replaced by now.-----First thing I look for on motors of this vintage.-----
 
Thanks I will give this a try. The coils are cracked on mine too, there is a sort of wax coloured covering which has cracks all over it. Does this mean they need replacing?
 
Yes, you are totally wasting your time till you replace those coils. On the good side, it hasn't been used for many years, so hopefully it isn't worn out.
 
That wonderful magneto was first used in 1950 and was still installed in the late 1980's------So parts are every where.----In stock at any reputable boat shop !!----Coils are cheaper than they were 40 years ago too.
 
Edchris177 said:
Skidder..Google Leroys Ramblings, he shows a detailed way to make a proper spark tester, out of scrap wire & a piece of 1x4.
Here is a post here from a few days ago, shows these cracked coils.
http://www.marineengine.com/boat-fo...6-1957-18hp-Fastwin-What-happened-to-this-one
Leroys Ramblings is for 9.9-15HP, but the spark tester is valid for any engine.
https://www.hisse-et-oh.com/system/.../Maintaining_Johnson_1974-1992.pdf?1360876515
Click to expand...

Thankyou, I will take a look at the sites. When I get the coils off later today I'll stick a photo of them in here.
 
I have taken just one coil off so I have the other to reference when refitting. This is the worst one and the section where the HT lead connects snapped right off when I took it out. They both look pretty grim. I think new leads, points, condenser and plugs may be needed. Still has the original? Pink Lodge plugs in it.



coil 2.jpgCoil 1.jpg
 
Thanks for all the help. I have replacement parts on order which I should have before next weekend. Hopefully the current lockdown doesn't delay this.
 
Received the new coils yesterday, fitted this morning and it fired on the first pull. I've had it running well this morning its just a bit smoky at the minute, i think i will try some better quality 2 stroke oil and confirm the mixture strength.
Thanks to everyone who offer information to get this old motor running again. I just need a boat now
 
Well done !-----Run at 24:1 if you want your grandkids to use it.----Run at 50:1 as per the 1967 brochure for less smoke ( more internal wear) shorter lifespan.
 
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