Trouble Re-starting

[old merc]

I have a 66' 50hp Mercury 500 that starts great, I run it for a while, go fishing and when I need to get to the next spot it really hesitates to start. I will finally get it going after 10min or so. Whatcha think???

 

[Don S]

Re: Trouble Re-starting

Could be lots of things. What sort of maintenance items and/or work has been done on the motor over the last couple of years. Tuneups, comperssion checks, carb repairs, that sort of stuff?

 

[old merc]

Re: Trouble Re-starting

Most recently replaced the water baffle on the exhaust side due to a pinhole. While it was off I checked the pistons and rings. All rings moved freely and looked really clean. Compression was good at the time. I've taken the carbs partially apart and looked surprisingly clean.

 

[OldMercsRule]

Re: Trouble Re-starting

Hey old merc, (I like your name), welcome to iboats. My mom had a 1967 Merc 500, and it was that year that size motor had the first generation "Thundrbolt Ignition". You can tell by the emblems and the surface gap spark plugs. There were points which had to be reset every 100 hours or so, (which triggered the electronic ignition), and if not: it was very unreliable. If yours is a 1966, (check the serial number to verify), you may have the older style ignition, (pre Thunderbolt). If so you need to do a complete tune up to find the problem(s). Make sure you have good grounds, (you may need to clean the grounding wires on the engine as well), due to the vintage. Good luck! JR

 

[old merc]

Re: Trouble Re-starting

The serial # is 1999693 which I believe to be a 66'. I'm fairly sure there isn't any points on my motor but have yet to really get too deep. I have never had any electrical probs with this motor, other than the starter, so I'm not too familiar with the electrical side. I have taken apart the carbs again and am going to double check my float levels. Will check all grounds though...good advise.

 

[OldMercsRule]

Re: Trouble Re-starting

Yep it looks like a 1966. Your going to have to do a complete trouble shoot. Me: I suspect those points! But you have to inspect everything starting with the easiest: plugs, (and while your at it: check the compression) then work from there, (check points, cap), then fuel issues pump, filters (carbs leak?) etc.. The points on that vintage need adjustment and inspection every 100 Hours. JR

 

[old merc]

Re: Trouble Re-starting

Thanks OMR. As I mentioned before, electrical is my weakness. Why does the motor start cold but not warm. Would a points adjustment fix this?? The points would be located in the distributor..right? My manual is a little sketchy on these. Looks like I forgot to mention that it doesn't idle all that well either, it will die if it gets below 1000rpm. Would the points be causing this as well?

 

[OldMercsRule]

Re: Trouble Re-starting

Hmmmmmm, That could be reeds the way you state the idle issues. Dunno how to isolate reed issues, (from a trouble shooting perspective), but the big guns on this site do! Check the points first, (yes:in the distributer). Do not pull wires out of the distributor cap as they are screwed in. Follow the procedure in the manual, as all my old Mercs have the newer style trigger so the specifics are above my pay grade. Good luck. JR

 

[old merc]

Re: Trouble Re-starting

Thanks for the insight. I will check those points. Would bad reeds cause the starting trouble as well? What exactly do the reeds do?

 

[OldMercsRule]

Re: Trouble Re-starting

They could. The idle issue is what tipped me there, (n' points could cause that too). I had a 1967 650 with the non point triggered thunderbolt ignition that had leaky reeds. It would not idle very well, but started fine. Reeds help the fuel mix to flow one way from the crank case to the top o' the piston, n' out the exhaust after the bang. You could have more then one problem, since the motor is over 40 years old. The non point Thunderbolt ignition Mercs do start better IMHO, and are far more reliable. When I'm collectin' old Mercs, (which I do more then I should), I specifically look for the non point triggered thunderbolt ignitions, as it eliminates what used to bug me about my Mom's 1967 500. JR

 

[old merc]

Re: Trouble Re-starting

If the reeds were bad, wouldn't I see fuel leaking from the front of the carb? A reed job looks like a last resort. Going to check the compression, points, carb, idle screw, float level, timing and do a de-carb just in case. Any thing else obvious I should check? Which order would you check it in? Thanks for all your help!!

 

[OldMercsRule]

Re: Trouble Re-starting

I don't think the reeds would cause fuel to leak, that would likely be the floats. The reeds are inside the crank case next to the mains. I don't know how to specificly isolate the reeds in a troubleshoot so one of the big guns will have to chime in here. As far as order compression should be first when the plugs are inspected and changed. The points should be inspected and adjusted next. The fuel system, pump, filters next. I don't think you will need to time it or tear the carbs down since it starts and runs and you did not mention the carbs leaking. On second thought, now that I re-read your posts: you did a partial carb tear down, why? If there is a problem with the carbs, they should be completely gone through, (as you may have blocked passages etc. or varnish). I hope some one else can tell you how to isolate the reeds in a troubleshoot as I dunno. Try a search for an old post addressing that subject. Good luck. JR

 

[Laddies]

Re: Trouble Re-starting

The mags on those older engine had a couple of problems with the caps, the early red and green caps were junk, yours should have a tan cap and rotor those were OK. As the engine warm up the hard starting can usally be traced to a bad condensor, once in awhile you will run into a bad coil but seldom, if you install points dwell them at 48 degrees if you have a dwell meter available if not gap at .011. The points cost about $40 but they last for everer sounds like your 66 ones ae bad already. Good luck - Bob

 

[Laddies]

Re: Trouble Re-starting

Sorry but I forgot to meantion that reeds don't come and go and neither do fuel problems with heat so if you are running and starting OK when cold the problem is ign.

 

[OldMercsRule]

Re: Trouble Re-starting

Thanks Bob, my guess was points. How do you tell if the reeds are bad on an engine? JR

 

[Laddies]

Re: Trouble Re-starting

OMR reeds act as the intake valve does on a 4 cycle engine the differance is, at about 1200 RPM the flow of fuel air holds them open and the are not functional above that speed
A bad reed will effect the 2 cyls on the mutual reed block and you will see fuel being slobbered from the mutual carb at idle but the engine runs strong at higher RPM thats why we run reed stops as open as possable on racing engines
If there is a crankcase fitting tou can ck for pressuse at idle. but I think it's just something that you have to experince a couple of time to get to reconize - Bob

 

[old merc]

Re: Trouble Re-starting

Thanks for your help guys. I've pulled apart the dist. and had a look in there. Cap and rotor contacts were a little corroded. I cleaned all contacts and reset the gap on the points, both you (Laddies) and my manual refer to a gap setting of 0.01. However, stamped on the inside of magneto it says to gap the points at 0.008. Which should I use? While I've got it apart is there anyway to check the condenser and coil?

 

[Laddies]

Re: Trouble Re-starting

New pts are gapped at .011 and to regap pts .008, the only way to get them set perfect is with a dwellmeter
Both the coil and cond can be cked with a merc-otronic or stevens tested the cond should be replaced while you have it apart this time

 

[old merc]

Re: Trouble Re-starting

OK took all advise and installed new points, new condenser and new rotor. I inadvertently moved the flywheel while the magneto was off. I should now re-do the timing as well? Do I have to check the spark advance as well or should it still work in the previous setting?

 

[old merc]

Re: Trouble Re-starting

BTW. What should compression be on this motor?