I have a Mercury 50HP outboard that doesnt like starting. Once it's going then it runs fine and never misfires or cuts out or any of the usual problem things. The engine is 20 years old. Anyone out there with any ideas?
Maybe I'm mentioning stuff you already checked but try:
1. be sure the fuel bulb is pumped up tight. Also be sure it's working, the original mercury ones from that era were made of rubber that goes hard, like the fuel pipe itself. Maybe change it for a new one, they're cheap.
2. Choke operation? If it's a remote model the choke is operated by a solenoid
3. Spark plug. I think should be a perma gap type, with annular gap. Massive gap, like 50 or 60 thou
4. Crap fuel. This is common. After 4-5 months in storage fuel octane falls off. Your engine should actually go ok on about 90 octane I think, but to be on the safe side dump the petrol and buy new. Towards end of season if you're gonna have petrol left over the winter use super unleaded (97-98 octane) as it lasts longer (for the same reason, always use super unleaded in your mower). On that engine unleaded is fine, you don't need lead in a 2 stroke
5. Carburetter - full service and clean out?
6. Use quicksilver lube oil, the other stuff is sometimes dodgy. Or use synthetic but mix at 70:1 not 50:1.
Frankly there's no much else that can go wrong with them, hardly any moving parts.
Is yours the original Merc style with the curved-wrap-around-band cowl, or is it the one with square-fibreglass-box cowl? Can't remeber what year they changed, early 80s I think. Let us know how it goes.
I replaced the fuel bulb purely because the original one had rotted and was actually leaking. Likewise I had to replace all the electrics to the engine because the hot wire has just disintegrated plus the engine wouldn't stop when you switched it off. The previous owner was using the choke to stop it.
The choke is solenoid operated and works OK but I find that putting the choke on actually hampers starting the engine. Is this because it's running too rich?
I have just replaced the spark plugs this very week in fact and have yet to see if this has made a difference. They are very strange looking plugs I have never seen any like this before!
I am using new fuel with quicksilver oil as like you I have found other stuff smokey.
I have not cleaned the carbs yet but I took off the float chamber to one and it looks clean. Can do this though.
Maybe I am worying too much as the engine does start it just seems lazy and takes a goodly few turns before it starts.
Engine has wrap around cover and is stamped XXX79 which I assume is 1979. But once it's going its fine and we have clocked the boat at 24MPH with a GPS so I don't think there are any majour problems.
Hmmm I was just guessing really. It could praps be running a bit rich, esp if closing the choke hampers starting. I mean you would normally need the chke for a cold start, but only for 5 seconds or so then you need to open the choke again. Where are you based? I know a few dealers who could do a good carb service.
If the decal is blue background, kind of dotty pattern that fades from blue to black along the length of the decal, with the letters mercury in silver all lower case including the m and vertical not italic, then it's a 1979. If the backcround is two-tone blue stripe, not fading from blue to black, with mercury letters in light grey (except the "50", they're in red), all upper case, it's a 1980.
I'm not sure about the number wiv "79" in it. Is that the serial#? Serial# for that era didn't contain the year so the 79 might be a coincidence. If you reply with the serial# I can tell you the year.
The choke buisness is right. I have to use it only for a few seconds then not at all. As far as the decals go I thought I knew the engine but now that you ask difficult questions I can't say for sure. I am going back to it over the weekend (hopefully) so I will memorise it.
With any good engine you should just keep the engine in good condition no matter what year, ie. clean the spark plugs,( a bit of sand paper does the trick), clean the carbuators as often as you can, (make sure ALL the jets are free!), check are compresion by removing the spark plug and stick your figure in the hole, SLOWLY turn the engine and you will feel the compresion,the stronger the better.If theres little compresion you might need new gaskets, a rebore and/or new pistons (only at extreme cases will you need new pistons).
Once all those are in good condition and in proper working order the engine will run for another 20 years.
I believe I have located problem. This came to a head when engine cut out while at sea and would not restart. I found that the cut-off cable which appears to short the points to the --ve of the battery was shorted permanently. This was caused by a loose wire within the remote control housing which was shorting to the case. This I fixed Sat and today (Sun) the engine stared on the third turn of the starter. However, I have also found that I need to replace a few jubilee clips on the fuel pipes as well. On a positive it runs a lot smoother with the new sparkplugs.
Thanks for your help.