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Author Topic: SC .61  (Read 6815 times)

peewee

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SC .61
« on: October 17, 2006, 11:07:44 PM »

Having just installed an SC .61 bought from e-bay in a 4 ft SeaQueen (some pics of this on my website) I am trying to get the thing started.

It did work on the bench - but was quite a monster.

I managed to start it in the boat this evening - using a rope - as the starter motor wasn't man enough while the engine was cold. Although it revved very high and wouldn't keep going with the glow plug disconnected.

The carb seems to have about 5 adjustments and I only know what the first two do:

1. Needle setting - 1 and half full turns seems to be about right for most engines - I'm OK with that.

2. Throttle - I'm OK with that

3. A (std) screw on the left side at the back - when I unscrewed this a bit it seemed to help. On another SC engine I have - but haven't used yet - this is held in position with a small nut. This engine did not come with the nut.

4. On the right at the back a (cross head) screw with a spring on it.

5. Inside the throttle arm a brass screw with a hole in it - I did fiddle with this - and wish I hadn't.

Can anyone tell what the various things do & where they should be set.

On the plus side, the mounting seems to be working really well and the various rubber mounts (all courtesy of Prestwich Models) keeping the vibration away from the wood.

If I can get the carb right I think that I will have a pleasantly fast boat.

advice would be very much appreciated




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w3bby

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Re: SC .61
« Reply #1 on: October 18, 2006, 07:22:51 AM »

Even though you didn't buy the motor from Prestwich, try Dave for advice as he sells the SC motors as well.

RC John

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Re: SC .61
« Reply #2 on: October 27, 2006, 05:01:18 PM »

To achieve Basic setting position for SC carbs.
Remove the carb and invert to see an elliptical slot in the needle tube.
Screw the "mixture" jet in to be central in the elliptical slot.
Close the main needle then open out two to two and half turns.
This should be your start position.
Loosen the glow plug half a turn if using a 12 volt starter.
Alternatively, use a 24 volt Sullivan with a SpeedMaster handle conversion for ease of handling.
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peewee

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Re: SC .61
« Reply #3 on: October 28, 2006, 10:17:58 PM »

John

many thanks - having looked at pdf files for similar carbs I have worked out which bits do what. When I return to my SC engines I will take your advice (in the meantime I have installed a Merco .61 in the Sea Queen & she goes really well).

regards

Pete
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glennb2006

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Re: SC .61
« Reply #4 on: November 07, 2006, 01:37:04 AM »

If it's working OK with the Merco leave well alone. SC is not too bad but they are hard to start when new (as you know) and they vibrate loads, which is most likely where your lock nut fell off the carb I would imagine.

In saying that I have got one with a tuned pipe on for playing around with and it does go quite well when running.

Good luck,

Glenn
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OneBladeMissing

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Re: SC .61
« Reply #5 on: November 13, 2006, 05:41:31 PM »

I have no experience of running SC engines, but (from what I hear) the tightness of all the bolts and screws on them should be checked before running.
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cbr900

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Re: SC .61
« Reply #6 on: November 14, 2006, 06:41:52 AM »

Even in aircraft they were prone to have bits drop off, so I put mine together with loctite 601, nothing ever came loose again...


Roy
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thedevil

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Re: SC .61
« Reply #7 on: October 12, 2007, 06:52:08 PM »

id say try a new plug
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glennb2006

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Re: SC .61
« Reply #8 on: October 24, 2007, 11:41:17 PM »

id say try a new plug

? What on earth.

Anyway, to business, finally got sick and tired of the SC 61 behaving like a spoilt kid, starting sometimes, not others, constant carb adjustments and idel all over the shop.

Splashed out on a TN2 carb from just engines.

Slightly smaller venturi, 1/2mm, so some perfomance will be lost.

Got it out the box, mounted the engine on the test stand and checked base settings, ie that fuel would flow.

Hooked it all up, applied starter and away it went. First time!!

The best bit is: It idles forever contiuously at really low revs if you want it to, has smooth mid range and a fairly linear opeing / throttle effect - ie, half throttle is somewhere around half revs - a novelty.

In short, I recommend this mod to anyone with problems witht he stock SC 61 carb.

20 well spent. It will be gettign wet on Saturday so if anyone is interested I will let you know how it goes on the water.

Glenn
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thedevil

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Re: SC .61
« Reply #9 on: October 25, 2007, 09:14:53 PM »

hi u may think a new plug is a stupid idea but when my sc 61 was giving me the same symptoms as you had i changed the plug and its run fine ever since.
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omra85

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Re: SC .61
« Reply #10 on: October 26, 2007, 08:36:43 PM »

Must agree with you on this Ben, many times a change of plug has cured throttling problems.
Always try to use the 'hottest' plug that will last in your engine.  The 'colder' the plug, the thicker the element, so if your engine is slightly too rich or too cold (especially on startup) the element does not keep hot enough to fire the incoming charge - hence poor tickover.
Next time you're in the model shop, look at the 'Firepower' plugs (evil things, but will do for this example).  If you look at an F6 and compare it with an F3 you will see that the F3 has a MUCH thicker body.  This carries the heat away from the element faster so is suitable for high nitro use.  If you use it for low (under 25%) nitro, you lose most of your throttling.
Other plugs use a different thickness of element to the same effect - compare a Rossi R6 with an R8 - the R8 has the thicker element for high nitro.
Compression ratios also play a part as the higher compression you have, the 'hotter' the plug needs to be.  So the big 90 on 25% with 25 thou head clearance will need the R8 but the 21 on 5% with 15 thou clearance will only keep the throttling with an R6.
That's assuming everything else is set up OK ........

Danny
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glennb2006

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Re: SC .61
« Reply #11 on: October 28, 2007, 03:01:48 AM »

Hello Danny / all.

Well it got to the lake today, zipped up on the starter with ease, idling nicely, put into water, throttling well, so let it go and all tickety boo, bt rich, which was fine, ran round, brought it in and leaned it off, away again, running nicely, boat handling like on rails and engine just perfect, did not miss a beat.

Drive shaft problem stopped the days play with this one in the end, but that was minor and now fixed. So, all in all, good run out with this carb. I'm a very happy camper amd I really do recommend this carb to anyone having trouble with their SC carb.

I appreciate your comments reference glow plugs earlier.

Cheers,

Glenn
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omra85

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Re: SC .61
« Reply #12 on: October 28, 2007, 12:40:22 PM »

Hi Glenn
Glad it all worked out.
Are you coming to Kingsbury (with it) on the 11 Nov?

I know the clocks have just gone back but posting at 4 am  :o :o 
(I assume you work nights - if not you really should get some sleep)  {-) {-)

Danny
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DickyD

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Re: SC .61
« Reply #13 on: October 28, 2007, 02:27:03 PM »

Hi Glenn
Glad it all worked out.
Are you coming to Kingsbury (with it) on the 11 Nov?

I know the clocks have just gone back but posting at 4 am  :o :o 
(I assume you work nights - if not you really should get some sleep)  {-) {-)

Danny

Never mind he posted at 4am Danny, he had already been to the lake.  ::)
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glennb2006

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Re: SC .61
« Reply #14 on: October 29, 2007, 12:34:16 AM »

Yeah but it took me an hour to get back from the lake, it was dark after all. I need beeter headlights on the boat, seperate topic.


In all seriousness, I posted at that time with number 2 boy on my knee screaming, 7 months old and finding teeth.

It would not comply with the rules for Kingsbury Danny, it's an old Prestwich Lightning FSRV with an SC 61 I am using for fun and as an intro boat for boy 1. It is not the fastest boat in the world, but it does turn well. It has got serious potential though.

I did, and still do, plan to race my Miami in OMRA, it has stock motor etc in and a few innovations on board, again, never going to be the worlds fastest, but I do hope next season to be able to attend with a model that is reliable and robust enough to make the complete course non stop. Think that should get some results. I know it is easier said than done. But that is my goal.
And it is going to be "D" class so on petrol.

Glad you posted Danny, I need to chase Martin for my membership.

Best regards,

Glenn



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martno1fan

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Re: SC .61
« Reply #15 on: October 31, 2007, 12:17:18 PM »

glad to hear the boat went well Glenn i have one of those sc.61 motors its a plane engine i installed a flywheel to and cooled via brass tubing coiled round the head.it runs great and the boat was pretty quick for a submerged drive too.no tuned pipe either,was a "xxxxx" to start with the electric starter though till i learnt the trick of loosening the plug hehe.you really do need to get some pics or video of your boats ,oh and cheers for the water piccup ill maybe install it over the winter.might get another video of my boat soon so ill keep you guys posted  ;D.
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glennb2006

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Re: SC .61
« Reply #16 on: November 11, 2007, 08:34:42 PM »

And the latest SC 61 update: after some pipe alterations yesterdat managed toget the engine working hard, revving well and really driving the boat hard. Best it has run so far.

Then is stopped. Very very suddenly. When it drifted in, a trun of the flywheel confirmed that all was not well....


Home to coffee and the allen keys out on the kitchen bench. (No idea why not the workshop!!)

Stripped the motor to reveal a snapped con rod.

Hey ho.

Anyone else had this happen on the SC61? I suspect i over revved it as it was very choppy, but took me by suprise. everything else looks fine and hope to be runnign next weekend to try to do it again!!


Glenn
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martno1fan

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Re: SC .61
« Reply #17 on: November 11, 2007, 10:53:10 PM »

sorry to hear that mate, these motors arent speed demons thats why i ran mine submerged just a thought.they seem to have plenty of power torque wise just maybe not good at higher revs.maybe try a bigger prop on it?.
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glennb2006

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Re: SC .61
« Reply #18 on: November 12, 2007, 12:56:19 AM »

sorry to hear that mate, these motors arent speed demons thats why i ran mine submerged just a thought.they seem to have plenty of power torque wise just maybe not good at higher revs.maybe try a bigger prop on it?.

It is submerged Martin, no big deal, stuff happens, couple of blurred pics.







Crank looks OK, but I ordered a new one too just in case.


More speed!!! :D



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GARY C

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Re: SC .61
« Reply #19 on: November 12, 2007, 09:27:51 AM »

Hi, been there many times  :'(

what fuel and total oil content did you use?

 may of started a hot potato here, lets see how the thread goes  O0

Gary.
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glennb2006

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Re: SC .61
« Reply #20 on: November 12, 2007, 09:55:08 AM »

Hi, been there many times  :'(

what fuel and total oil content did you use?

 may of started a hot potato here, lets see how the thread goes  O0

Gary.


Hi Gary,

at the time of the failure it was running on Duraglo straight, normally run Duraglo 5%. Engine had about 4 hours on this rod. (Well, on the whole engine)

When you say you have been there many times, do you mean with the SC motor?

Cheers,


Glenn.
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GARY C

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Re: SC .61
« Reply #21 on: November 12, 2007, 11:39:08 AM »

Hi Glenn,

Duraglo is fine for your SC, total oil is 15%   - 9% E.D.L. and 6% castor. Please dont run any engine too lean, on your SC better to run it slightly on the rich side. When the boat is runnig full throttle it is nice to see a light smoke form the exhaust, indicating that the oil is comming through.  O0

Some people will say that this is like running on chip oil but as you are sailing for fun it is fine.

Using the frase " been there many times " has no connection to the SC. The weekest link on any two stroke model engine is the conrod.If you wish you can put a time scale on conrods and bearings and replace them as preventive maintenance.
I have broken many conrods through the years.

Make sure you flush out yor engine as there could be small debris of alloy gone into the bearings. When finished running your engine always flush through with after- run oil, pour through the carb and the plug hole, then spin engine over with your starter motor. Or when engine is running on low idle, pour after-run oil down the carb untill the engine stops.
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glennb2006

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Re: SC .61
« Reply #22 on: November 12, 2007, 12:09:09 PM »

Hi Glenn,

Duraglo is fine for your SC, total oil is 15%   - 9% E.D.L. and 6% castor. Please dont run any engine too lean, on your SC better to run it slightly on the rich side. When the boat is runnig full throttle it is nice to see a light smoke form the exhaust, indicating that the oil is comming through.  O0

Some people will say that this is like running on chip oil but as you are sailing for fun it is fine.

Using the frase " been there many times " has no connection to the SC. The weekest link on any two stroke model engine is the conrod.If you wish you can put a time scale on conrods and bearings and replace them as preventive maintenance.
I have broken many conrods through the years.

I do run slightly to the rich side. I think that what has gone wrong is that as it was choppy and I had shortened the pipe quite a bit, the motor was revving well but the prop was leaving the water a lot and unloading the motor, which was then revving probably a bit more than it is designed to do.

Yeah, going to give it a good wash out, got the crank out and just waiting for the spare con rod. I do use after run when I put it away.

Make sure you flush out yor engine as there could be small debris of alloy gone into the bearings. When finished running your engine always flush through with after- run oil, pour through the carb and the plug hole, then spin engine over with your starter motor. Or when engine is running on low idle, pour after-run oil down the carb untill the engine stops.
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ids987

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Re: SC .61
« Reply #23 on: November 12, 2007, 01:27:13 PM »

Glenn,

If I were you - unless you've done it already, I'd replace the bearings for decent ones (rather than originals) - while you've got the engine apart. The SC bearings (in my opinion) are one of the main weak points of the engine anyway, and you've already changed the carb. I'm guessing you've checked the bearings for "feel" already, but excessive bearing play in itself can cause rod breakage. Obviously if the bearing breaks up, it's worse. I have known a relatively new SC bearing to break up, and trash the piston and liner. Plus the likelihood of shrapnel from the rod in the bearings (as Gary said).
In my time, I've broken about four rods in various engines. One of these was caused by a knackered bearing. All of the others, as far as I could ascertain, were caused by getting water in the engine whilst it was running - one way or another. It might be worth considering if yours could have "had a drink" ?
I have seen a SC rod break through overreving, but that was "on the deck", and in a brand new engine (hence very tight piston / liner fit). Notwithstanding that, any rod will break if you rev it enough, and SCs are not really designed to scream (although I reckon I've seen a SC .61 survive short runs of 20,000 RPM - or close to it, on the water), so your "out of water experience" - on the chop, may have done it.

Good Luck:
Ian
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glennb2006

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Re: SC .61
« Reply #24 on: November 12, 2007, 05:03:26 PM »

Hi Ian,

yes, the bearings feel OK and are now clean, as is the rest of the crankcase. Not a bad idea changing the bearings, my only reservation being that the old bearings will be destoyed during the removal process, so I hope that I can get the new bearings from stock.

Glenn
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