problem with johnson 25 hp

stevemorley · 10 July 2010, 02:39

I recently bought a 25hp 2 stroke johnson 2002. I ran it twice really well then it seemed to drop a cylinder, it now starts and idles badly and i can sometimes get it to rev by hand but under any load it just splutters and sounds hollow. Some tiimes i can get it to rev high and i think i must have cracked it as it sounds ok then it goes back to idle and has trouble revving up again just like it is starved of fuel. The tank was very sludgy so i have flushed it out and changed filters etc. I have flushed through the carb and pump etc. There seems to be an oily fuel mix dripping out of the front of the carb, the botton plug is really oily and the top one normal/sooty so it does not seem to be firing on bottom plug. I have swapped over coils and its the same and changed plugs. They have had head off and also checked reed valves which they said are ok, they are now talking about stripping the powerhead and my wallet is becoming nervous. There is a pipe going from the carb into where the reed valve is and if i run it with that pipe off fuel seems to spit out of there and i dont know if thats normal or not. Any help or advice would be much apreciated. Thanks

outboardtech · 10 July 2010, 08:52

Hi , check your BASICS first and try dignose from there . there are ONLY three things that can make an outboard RUN and RUN well .these are COMPRESSION , FUEL and IGNITION ( SPARK ) Firstly what are the COMPRESSIONS on this ? have you got a spark tester to check spark ? Lets go from there , RESULTS CHEERS

stevemorley · 12 July 2010, 21:40

Many Thnks for the reply. The engine is currently in with a repairer and I went over this weekend to have a look, he had the cylinder head off and also the reed valves were exposed and he said tomorrow he is going to whip the flywheel off to see if the timing key had jumped so I guess I am pretty much in his hands ! It does not sound good as I thought it was just going to be a bit of s--- in the carb. I will keep you posted. Steve

9D280 · 13 July 2010, 14:07

Quote:

Originally Posted by stevemorley

There seems to be an oily fuel mix dripping out of the front of the carb,

Is your float valve floating / set correctly?

Not sure the details of this machine, but if it has separate spark plug leads, did you check (swap) them too?

stevemorley · 13 July 2010, 21:48

Thanks. I had the boat shop on the phone today who said that they can not fix it so I am picking it up tomorrow. I did not swap the leads so as you say will try that as soon as possible, they told me compressions were good at 115 each and I will also maybe buy a couple of new coils to see it that does the trick. If the bottom plug is oily and compressions good it surely can only lead to an ignition problem. Would the unburnt fuel be coming back through the carb a bit blue and oily looking, as I mentioned that there is an oily residue dripping slowly out of the front of the carb when engine is running ?

Thanks

9D280 · 14 July 2010, 10:35

It's the stuff out the front of the carb that makes me think there's too much fuel in there to start with, although the shop I would hope checked all that out. If it doesnlt look like the carb(s) have been off, check your float (compare the bottom one to the other(s)- also check the needle valve. If that isn't closing properly, what happens is the bowl essentially sees fuel pump pressure, and so there's a higher pressure difference across the jet, and so more fuel flows into the engine thru' that carb.

As you say, oily plug would hint fuel is getting in there, but just not burning (or too much fuel to burn). If you have a spark friend, it's a good idea to do a "megger" insulation test both on the leads and across the plugs (connection to threaded bit) A normal multimeter will say that insulation is good but when you chuck a couple of thousand volts at it, you get a whole differnet story. Having said that, swapping them and "chasing" the problem works just as well, but does need some water to play on!

outboardtech · 14 July 2010, 13:27

Check all tha BASICs first . NOT sure WHY boat shop said they cant fix i ??? any reason WHY ?? a good tech will do the basics first . have you got GOOD SPARK ?