Silver Century 75 stopping during run

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Janzip
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Joined: Thu Sep 21, 2017 9:25 pm
Location: Finland

Silver Century 75 stopping during run

Post by Janzip »

Hello everybody,
I'm new on this forum and would like to know if anyone has an idea on what might be the problem with my ESC 2231 AAO Silver Century 75. I bought it two months ago, cleaned the carb, fresh fuel in the tank and off we went. It was performing well except that very little cooling water was coming out of the cylinder. It would, though, run well for long periods. Lastly there would come no water anymore but a sort of steam so I decided to give the Seagull a thorough service. Stripped it down totally except the crankcase, crankshaft and con-rod, as there was no evident play anywhere in these parts. The waterways in the cylinder were all full of rust etc, cleaned them out as good as I could. The cylinder bore, piston and rings were almost as new, honing marks could still be seen in the bore. As I had no new head gasket I heated the old one cherry red and dipped it into water to get it soft again. Done this countless times on other copper and aluminium gaskets, has worked well. Checked the straightness of head and cylinder top. Used instant gasket sealer on both sides of head gasket, but only for the waterways, not on top surface of the cylinder liner itself. I have bad experiences on using it there, from other engines. Assembled the whole thing, started first pull as it always does. After running it warm for a couple of times i re-tightened the head bolts, done this twice. Everything seems to be fine. Cooling water flow is good even at tick-over.
Now the problem: after running it om my boat for 30 to 40 minutes it stops. It doesn't stop in a way that the spark would die out, suddenly, like in half a second, it stops in a way that takes from one to two seconds, if you understand what I mean. Difficult to describe.
If I immediately after the stop turn myself to the engine, pull the rope (has a recoil starter) it starts first pull and works for 10 minutes. Good compression felt on the rope. Then stop, start, runs in 10 min periods as long as I want to. I have the opinion that if the fault would be an electric one, it would start only after cooling down. (the ESC has pointless ignition)
I have tried with another tank, from a moped,hanging from a lenght of tubing with petrol cap removed. Same symptoms, no help. Have cleaned the carb several times and tried an in-line filter on the petrol hose.
Have tried other plugs with different heat ranges.
Head gasket? As mentioned I softened it and have re-tightened the head bolts. Tried spraying a soapy solution all over the engine to find out if there was a leak. No bubbles visible. Leaking into the water jacket? I attached a piece of hose to the water outlet, other end to a clean 10 liters water can, covered the mouth of the can with a rag so that just a little air could get out. Run it long enough to half-fill the can, stopped and sniffed but no smell of exhaust fumes could be felt. Kept the water in the can for a week, no oily deposits would float, as there would be if exhaust fumes from a leaking head gasket would go into the cooling water.
The symptoms are the same if running at half throttle.
Could it be the pointless ignition module? Why does it re-start, then, without cooling? If there would be a leak in the crankcase that would appear after 30 minutes running why does it re-start? I mean, after stopping and re-start there's only five seconds.
Also remember that it was working well with the waterways all clogged. What have I done wrong with the re-build?
In my opinion a two-stroke needs fuel, air, top-end and crankcase compression plus a good spark for running. These are all there.

Regards,
Janne Petersen
Helsinki, Finland
Liam2k3
Posts: 87
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Location: Lancashire

Re: Silver Century 75 stopping during run

Post by Liam2k3 »

Hi , im new to seagulls but i had a honda outboard 7.5 that used to just cut out for no apparant reason and restart straight away. It turned out to be the cdi unit. But there are people on here with much more seagull experience than me who may have seen this before and it may be something you can fix rather than replace.
Keith.P
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Re: Silver Century 75 stopping during run

Post by Keith.P »

It sounds like a fuel problem rather that the CDI, it may just be a float problem.
what I would do is, plug a timing light or spark indicator on the HT lead and run it, if it still shows a spark when it starts dying, then its not the CDI, then you will know if that's the problem.
Have you cleaned the fuel filter out, on the side of the carb?
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seagull101
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Location: Scottish islands

Re: Silver Century 75 stopping during run

Post by seagull101 »

I would try cleaning the fuel tap filter. it may be that when running dirt is being sucked up against the filter then when it stalls the dirt instantly drops down the the bottom of the tank.
I had the exact same problem on my grey fergie tractor!

Another thing to note is that these cdi ignitions are usually dead or alive, not half dead.
Is it MK3 or MK4?
also is it a 416 carb or twin jet?

Jacob
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Charles uk
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Re: Silver Century 75 stopping during run

Post by Charles uk »

Jacob it's a 1990 so it's Mk4 & a 416.

Janne have you looked at the CDI? does it have a stop button wire hanging loose or tied in a knot?

The stop button wire on a CDI should be removed on motors not fitted with a stop button.
Make it idiot proof and someone will make a better idiot.
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Nudge
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Re: Silver Century 75 stopping during run

Post by Nudge »

I posted this in the other double thread (so I have copied it to here. the other thread needs to be deleted.)

What fuel mix are you running it on? 10:1 or 20:1 or....?
Take the plug out and look at the colour, is it black? It almost sounds like a fuel problem.
If it was the spark module I would have thought it would sound like it was missing?
"THE KING OF BLING"!
Is it better to over think, than not think at all?
Janzip
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Location: Finland

Re: Silver Century 75 stopping during run

Post by Janzip »

Hello everybody and thanks for the answers.
Haven't been out with the boat as we just had a snowstorm, 20 cm of the white stuff and temperatures well below zero. Must wait for a couple of days until it gets warmer. Meanwhile I found out that the HT cable was not properly attatched to the plug cap, I have the type that covers half of the plug, inside there`s a sort of long cable shoe with a hole. You aim the cap centrally on top of the plug and then tighten it by a nut twisted by your fingers ( this is not an easy job when it's dark, freezing cold, windy and snowing). Anyhow, I cleaned the end of the copper core and the inside of the cable shoe and soldered them togeteher. Let's see if that helps with the original problen, I doubt it.

-Lam 2k3: Thanks for the tip, that might be the reason. If the problem still is present and nothing else helps I must order an ignition unit and try it out. (Here's one more reason why I try to avoid electronics on engines. If it's got points, condenser and a traditional ignition coil you can measure them, heat in the oven and see if any values change etc. They are repairable! With electronic ignition you just change the whole thing and hope for the best.)

-Keith.P: Thanks Keith, did'nt think of that. I have a stroboscope pistol and will try that, povered with a motorcycle battery, as soon as the weather gets better. Will inform you about the results.
?float problem? In that case the float needle gets stuck in the valve and doesn't let petrol through. I could hang my loose moped tank higher, like one meter, that would give a pressure of 0,1 kg/cm2 in the fuel line at the carb. Or then try an electric fuel pump adjusted to 0,2-0,3 kg/cm2. This pressure should be enough to open a sticky valve.
Now when i'm thinking of it, sometimes when the engine has stood for a couple of days and I try to tickle the float prior to starting, nothing happens, no fuel flow visible in the transparent fuel hose, even if i tap onto the carb with a small spanner. When I squeeze the hose between my fingers the fuel will slowly start to run. When cleaning the carb i have examined the float needle with a watchmaker's magnifying eye. Seems to be OK. Maybe order a new one? Has anyone put a plastic hose beside the carb for to see how high the fuel level is in the bowl? What would be best place to attatch the hose, would'nt like to drill any extra holes in the carb?

-seagull 101: Hi Jacob, the whole fuel system including tank and all filters has been thoroughly cleaned, many times. Please also remember that I have the same symptoms even if I run it with another tank taken from a moped. I also have tried a longer fuel hose wound in a couple of spirals so that any dirt or water collects to the lover loops. This I did as I thought that maybe the extra filter that I use in the hose would not let enough fuel through.
You are right, normally electronic ignitions die totally when they die. But anything is possible, refer to Liam2k3:s answer.
The ignition is probably a Mk III (I'm no expert on that!) and the carb is a 416.

-Charles uk: Hello Charles, according to identifications my ESC 2231 AAO Silver Century 75 is from 1980, not 1990 as you mention. I might be wrong, though, has anyone some ideas?
I have not found a stop switch cable on the engine, I wish though it had one, a stop switch can sometimes be handy in emergencies, lihe if your throttle cable is stuck.

-Nudge: hello Nudge, I'm running on 1:25 using a well-known brand of Super Outboard (mineral) oil. The plug is always clean after a run and has a brownish-tan colour. I have experience in tuning two-strokes and in my opinion the fuel/air mixture is as it should. If I restrict the air flow at the carb intake a little with a finger the Gull starts to four-stroke and loses revs, so it's set a bit on the rich side but that's better than running lean. Also if I look at the plug when it has stopped by itself the plug is clean.
Sorry for my bad understanding in English but does "I would have thought it would sound like it was missing?" in your answer mean that the engine would not run smoothly, misfiring? If so, the answer is that it runs very good until it suddenly stops.

Now I'll go to the boat and shovel the snow out
Regards
Janne
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Charles uk
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Re: Silver Century 75 stopping during run

Post by Charles uk »

Janne your right sorry!

Only CDI's for the 170 series & the QUB's had provision for stop buttons.
Make it idiot proof and someone will make a better idiot.
Arbian
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Location: Perth

Re: Silver Century 75 stopping during run

Post by Arbian »

Charles, Did all the mk4 ignitions not have this ability? From my small collection of motors switch from mk3 to mk4 seems to be around 1986??? I keep meaning to try and fit a stop button to one but have not got round to it.
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seagull101
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Re: Silver Century 75 stopping during run

Post by seagull101 »

I have a stop button for my model 75, i'm probably going to make a bracket for it on a crankcase bolt.
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Charles uk
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Re: Silver Century 75 stopping during run

Post by Charles uk »

Only Mk 3 & 4 CDI's that were fitted to motors with a stop button had a CDI with the wire when they left the factory, earth the wire & the motor stops or won't start. (125, 175, SD110, SD160, Curlew, Osprey, Kingfisher & 5R)

Nowadays if your buy a new CDI from John Williams it will have the wire, which should be removed if fitted to a motor with no stop button.

If your stop button gets wet, the motor will stop!
Make it idiot proof and someone will make a better idiot.
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