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1965 merc 50 hp no spark

Wet as in wet with fuel? If water, that's a problem!

Perhaps the bottom 2 cylinders are being "washed" with too much fuel.

Does either carb leak fuel out the throat when you pump up the primer bulb? Or any fuel run out of the carb while the motor is running? If so, that carb's float needle is leaking and needs to be adjusted/replaced/float checked.

Black plugs usually are from carbon buildup, are they firing (could be fouled)?

Are all the plugs hot after running the motor, or are some noticeably colder or hotter than the others?

It sure sounds like some cyl's aren't hitting, just trying to isolate it to the bottom or top carb (or something in-between).

To post a vid you'd need to do so at YouTube or other vid hosting site then post the link here.
 
I'll have to check the spark plug temp on Friday. It seems to be running on all cylinders (runs smoothly through all rpm ) but I'll check with a spark tester. When I prime the motor with the bulb it becomes firm and the carbs don't leak while priming or while running, only when timing the motor while trailering. One thing that I didn't mention is that when starting it pops occasionally I guess igniting the fuel in the exhaust. I'll take a complete video if startup warmup and full throttle on Friday or Saturday. I'll order a diaphragm pump kit and install before I run it. CaNT hurt. It sat for 15 years. Thanks for the help
 
Sounds like it is running pretty good. Get one of those tach timing lights and see what the WOT rpms are. Do you have a gps looks like it is scootin along pretty good
 
Is that motor all white with a black wrap around? What is the serial number on the motor? Maybe is was the sun but the last year for the white motor was 1963. The best looking motor made in my opinion.
 
Serial # is 1620898. With 2 people it goes under 4mph by my self it dose16mph. It dose run smoothly just seems to dog with 2 people. I also was told it was a 1965, it could be a 63. Other boats with 50s on them (18footers) on the lake seem to have no problem with 4 people. A few are 1970s mercs but 2 stoke as well.
 
That puts it at 1964 probably built in 1963 having the white paint. You can likely get a timing light tach it may be over propped for your boat. Finding a different prop could be a real challenge. I had a 40hp johnson on a 16ft fiberglass that would reach 20mph on a smooth lake with no wind normally 16-18mph.
 
Did you check to see if the carbs are opening fully at full throttle? The as the distributor on those goes to full advance and hits the stop, the part above it keeps turning until the carbs are fully opened.

A common problem is that the grease inside gets hard over the decades and that part won't move. I've had to heat the top of the distributor tower with a torch to melt the grease, then pump some new stuff in, to get it moving.

Jeff
 
Rotates freely very clean and smooth. Having trouble locating diaphragm and other parts, any suggestions on suppliers for parts on old motors?
 
So finally got it through my thick scull that it is the lower 2 cylinders not firing. There is definitely spark. The fuel bowl is filling up but nothing out of the nozzle. Pulled the carb and cleaned dismantled then reinstalled but still no visible fuel from nossl. Needle valve seems to be set properly and clean.
 
Do not run this motor untill you sort out the carburetor / fuel pump issue.---------Remember no fuel going in means no oil also.-----------Bad things will happen !
 
..."Could a bad fuel pump be causing lack of power at speed?"

Sure. So can a plugged fuel filter and other things.

Jeff
 
Sorry, had a couple of drinks last night. Pulled the carb again and c
Cleaned and blew through all the nozzles and all seem clear. There was fuel in the bowl at the hight it should be. So I have spark, I have fuel and fuel on the plugs but no ignition on those bottom 2 cylinders. Fuel pump seems to be good but that's the next thing I'm going to check due to its age
 
Well just realized that I'm a bone head. When I installed reinstalled the distributor /magneto I reversed the 3 and 4 spark plug lines. Needless to say it's firing on all cylinders now. Next back in the water. Thanks for the help
 
Took out on the lake and started slow let it warm up and now with 2 kids my wife and I hits 20mph without evendors working. Actually think I need a more aggressive prop. Took it back out with me only and 28 mph. I'll post a video tomorrow
 
It's a 4 cylinder 2 stroke with 2 carbs. I was having trouble with the magnito distributor getting a spark. I replaced the condencer and cleaned all the points. I reinstalled it in the motor and eventually after many mistakes I got it running. Once on the water though the power wasn't near what I expected. I've been back and forth with members trying to figure it out until finally this morning I noticed that the lower 2 spark plug cables were numbered and that I had the # 3&4 cables reversed from when i installed the magneto over a month ago_Once I changed them the motor came to life. Lesson learned. Check the basics first
 
Can you make out the pitch number on the prop? Usually it's stamped into the body.

You only have 50hp to work with and unless it's achieving the proper rpm at full-throttle with light load (i.e. only the driver), it'll be "overpropped".

Good indication of that is the speed difference with just you and with passengers. If the motor were running in its powerband you'd never lose that much speed with pssgrs.
 
I guess it's the proper prop. Think Maby I'll just leave it alone, running beautifully. I'm not sure if you read the last few posts but I had to really swallow my pride. Forgot to check the basics. Thanks for the help
 
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