A seagull afraid of the water

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Mantulaman
Posts: 6
Joined: Thu Jul 04, 2019 12:02 pm
Location: Perthshire

A seagull afraid of the water

Post by Mantulaman » Thu Jul 04, 2019 3:56 pm

Hi folks,

First post so be gentle!

I recently acquired two silver centuries and a big box of bits and have set about on their restoration. After a complete strip down, clean and polish I have the first motor back together again with new gaskets, plug etc. Initially it had a leaky float needle seat, a leaky fuel tap, a bent crankshaft and an impotent ignition coil. All of these issues ha e been sorted but she still won't run when she's in the bin.

If I pull the rope with her on the bench she whirrs to life and sings away. If I do the same with the prop in the water she will fire 3 or 4 times and stall. The prop isn't too deep and I have even tried raising her up until the exhaust is only just under the water but still no joy.

I've checked the points gap, timing position dimple, plug gap, and cleaned the fuel system properly but still no joy.

It feels like fuel starvation but unless there is a vacuum leak I can't see why it wouldn't be getting enough fuel. The throttle cable screw on the top of the carb is a little wobbly so I wondered if it could be a problem?

Any and all advice very much appreciated.

tambikeboy
Posts: 820
Joined: Sat Oct 29, 2016 2:01 pm
Location: Scotland

Re: A seagull afraid of the water

Post by tambikeboy » Thu Jul 04, 2019 5:10 pm

Have you tried it without the prop fitted wee all like pictures .
(Another Scottish seagull the number's are growing) :evil: :twisted:
Roll me up and smoke me when I die
Regret is just a memory written on my brow

Mantulaman
Posts: 6
Joined: Thu Jul 04, 2019 12:02 pm
Location: Perthshire

Re: A seagull afraid of the water

Post by Mantulaman » Fri Jul 05, 2019 12:50 pm

Yes it does but like a bag of spanners. Seems to have no power and is lazy to pick up revs when I open the throttle. I read on the SOS website that adjusting the points will adjust the timing as the points will close sooner/later as they pass over the lobe on the flywheel. After some mucking about with the gap I can't make it run much better so wondering if the replacement coil and points from my box of bits are also gubbed. The other century is waiting for its turn so I may rob the coil and points off it to see if it improves the situation. I also tried spaying some carb cleaner into her before starting but it made no difference. I had the base plate off last night to check the dimple and that it was in the right place and all seems fine with that too...

That strap line on the starting pulley really does mock you when the thing won't go!

Mantulaman
Posts: 6
Joined: Thu Jul 04, 2019 12:02 pm
Location: Perthshire

Re: A seagull afraid of the water

Post by Mantulaman » Fri Jul 05, 2019 5:46 pm

Ok, so a little more mucking about and I found a problem. There was a washer under the locking screw on the points so as it was tightened it would lift the dowel under the pivot pin and allow the points to move out of adjustment as the flywheel spun. I removed the washer, adjusted the points and tightened them down and she will now run with the prop in the water but only just above idle. It won't rev high enough to allow the water pump to work so I can't run it for long like this. I have a lightweight seagull in the workshop that belongs to a friend and it's full of life and makes this thing look like a dead duck.... After not long running I can see oil seeping out between the two halves of the crankcase so wondering if my piston rings are shot. Thinking about it the bent crankshaft would have put all sorts of torque on the connecting rod, piston and rings so it's likely and all my puff is just blowing past into the case.

andrew
Site Admin
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Location: Greenwich, USA

Re: A seagull afraid of the water

Post by andrew » Sat Jul 06, 2019 3:30 am

Could be poor seals on the crankshaft housing causing performance problems. This was addressed recently on another thread:

viewtopic.php?f=2&t=6782

Journeyman
Posts: 106
Joined: Thu Aug 16, 2018 6:26 pm
Location: Pembrokeshire

Re: A seagull afraid of the water

Post by Journeyman » Sat Jul 06, 2019 9:21 am

As Andrew suggested it could be a problem with the crankcase seal.
The 40 plus I bought this year had a badly damaged case, the previous owner had slathered fillers over the outside and used it like that. I scraped and chiselled the fillers off to see what the problem was.
The engine still started and ran even with such a big gap that the escaping air was enough to dimple the skin on my finger. But it was down on power!
Fitted a good crankcase and it now runs well. If you split the crankcase and use some engineers blue it will tell you how the fit is and you can adjust the fit with scraping.
Outboard 071.jpg
Dave.
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Mantulaman
Posts: 6
Joined: Thu Jul 04, 2019 12:02 pm
Location: Perthshire

Re: A seagull afraid of the water

Post by Mantulaman » Tue Jul 09, 2019 10:48 am

Thanks guys, I was surprised that the motor didn't have a gasket between the two halves of the crankcase.

I bought a cheap compression guage and it only shows 25psi when I spin it over with a drill so I'm guessing the rings are shot as the head gasket is new and I don't see any sign of leaks from there. The base gasket on the other end of the cylinder is also new and it appears to be sealing.

Mantulaman
Posts: 6
Joined: Thu Jul 04, 2019 12:02 pm
Location: Perthshire

Re: A seagull afraid of the water

Post by Mantulaman » Tue Jul 09, 2019 10:51 am

I will check the crankcase fit when it's apart. I don't have any engineers blue so I'll have a go with a sooty flame to blacken the surface. Not tried it before but it's how seals on shotguns are checked so should work fine and will save me from buying the blue.

Horsley-Anarak
Posts: 2748
Joined: Thu Aug 07, 2008 8:42 pm
Location: Surrey

Re: A seagull afraid of the water

Post by Horsley-Anarak » Tue Jul 09, 2019 9:51 pm

You don't need engineers blue.
Just clean the surfaces and use a permanent marker pen.
Then find a flat surface and some wet and dry (400 to test 240-180 to flatten).
Flat surface can be nice granite worktop, piece of glass or shiny porcelain tile, couple of rubs will let you know if the crankcase is damaged, they normally distort at the tiller mount when the engine has fallen over.

Mantulaman
Posts: 6
Joined: Thu Jul 04, 2019 12:02 pm
Location: Perthshire

Re: A seagull afraid of the water

Post by Mantulaman » Tue Jul 23, 2019 8:19 pm

Ok, so pulled the whole top end to bits again, connecting rod was bent but luckily had another one in my box of spares. Checked the fit on the crack case while it was apart and it was like a sieve. Got a tile and taped some 320 grit to it and flattened both halfs with a figure 8 motion. Put it together without the crankshaft and used a torch inside to check the fit. There was still one spot that I could see light through so I peined it over with a drift and it looked fine. Filled the crankcase with water to see if there were any drips and it was solid. Decided to refresh the studs that hold the crankcase to the block as the threads are chewed so it wont go back together until they arrive. Making progress so thanks for your help folks! :)

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