Engine help please!!!

[lukewhiting]

Took my thundercat out a few weeks ago, started fine & ran perfectly.....until i took it up to full throttle. thats when it wouldnt gain revs & ran really lumpy! Its fine on idle upto 3/4 throttle then it goes lumpy!
i havent had the time to have a proper look at it yet but wondered if anybody on here had any ideas? Its a tohatsu 50 if that helps?

before i took it out i changed the kill switch unit & spark plugs. i checked the old set of plugs & still had the same problem so cant be them & dont think it could be caused by the kill switch unit at all?? but i dont know...im not amazing with engines, just know the basics!

[yam man]

Sounds like a carb issue be worth strip and clean carbs and sync

[longjohn]

Check that the throttle or gear levers & cables are not fowling the fuel line - you may have dislodged something when you removed/replaced the engine cowl.
Sound like fuel starvation of some type - is the priming bulb firm - fuel filter..?

[clydeoutboards]

Hi

it does sound fuel related so thats where I would start and why you are at it you might as well clean the carbs and change the gear box oil i.e. do a basic service as this is never a bad thing.

more things to do / check here Servicing | Glasgow and Clyde Outboard Services Outboard Engine Servicing

[lukewhiting]

Thanks for the help! Ill get it of the garage soon and take a look for any of these things.

Could it be anything to do with the coils? I touched them with dry hands & still got a shock of the rubber cap, which showed it was arcing. But then a few days later when i had another small look there was nothing???

[Turbodiesel]

Also check your getting full throttle advance on the stator (under the flywheel) this engine has a habit of this part seizing up and not giving you full throttle advance on the ignition.

[lukewhiting]

Originally Posted by Turbodiesel

Also check your getting full throttle advance on the stator (under the flywheel) this engine has a habit of this part seizing up and not giving you full throttle advance on the ignition.

Yeah ive had alot already with the engine but this is different

[lukewhiting]

So went upto the garage today. Theres no water up there so couldnt start it up but checked the whole pinched feul pipe thing but all the pipes are away from the throttle linkages & any moving parts so geuss that rules that out.

[PeterM]

An easy one to check , are all the HT leads in good condition /secure ? They can breakdown under load and give all sorts of buggering about ....

If the change of plugs was the start of the problem the leads could have cracked / split in being pulled etc ...put back on , off again to swap the plugs back and on again etc

[bingosucks]

you can buy ht testers,just place on plug and ht lead (about £10 from most halfords type places) could be coils not firing correctly or maybe your carb

[bingosucks]

4 PC HT SPARK PLUG SOCKET TESTER LEADS SEALEY VS5261 | eBay ramp the engine up one might only be failing at higher revs but will allow you to check....your looking for a nice dancing spark

[yam man]

As said before it sounding like carb fault

[paddlers]

Had similar on my Mariner, turned out to be the bottom plug lead shorting in the cowl support !! Swopped the leads & problem sorted although as already said could be fuel !! Are the plugs all similar colour as mine was obviously not firing properly & looked oily with the faulty lead?