Merco 61 tips

I've got one of the "light case" Merco 61's I hope to be running for the first time in the near future. Does anyone have any tips for running one of these brutes.

Get Dave Royer to comment. His Merco 61 is one of the sweetest running 4-2-4 engines I've ever seen.

I've had a couple of these things run well with a .290 ......312 venturi on 10% fuel with a 12x6 or 13x6 Zinger,APC prop.

I am hoping an APC will work well since they are readily available locally.

You can take an APC 12x6 or a 13x6 & cut it down to 12x6 (which I prefer) or of course use a full 13x6.

There is an APC 12.5 x 6. It works real well on my 2Star .60bb. It's easier to order online from APC than drive 10 miles to buy one. They have sizes you'll never see at the LHS, prices seem to be the same or awful close, and (so far) they've never been out of stock. Still, if you can get what you want from the LHS, it's good to at least try. Steve

They run just fine when stock. I prefer the light case, but I canabalize one of the heavy case/steelfin ones for the dykes ring piston. It's also a good candidate for boring out to about 0.965. It can take up to .315 venturi on a 13-6. For a 0.300 or below, I would stay with a 12-6.

LAST EDITED ON Feb-12-04 AT 04:04 PM (CDT)
 
Just wondering what vintage Merco 61 the "light crankcase" is? Is it a new engine or one of the 60's early 70's production?

I acquired mine in a package deal which included a Cox RR-1, some Golden Bees, Veco 19's, Veco 50 etc., all older stuff, so it must be one of the older Merco's.

Thanks Elwyn. Was wondering how new it was. I have a couple of that vintage of the mid 60's. One is a 61 (well used) and a 49 which is near new. They were great engines and I used them from around 1964 to 1971. After Tom Dixon was here in OZ at our nats in 1994 (about) I got hold of a BLACK CASE 61. The worst example of an engine I have ever purchased. Works great as a paper weight! IT WAS NOT ONE OF TOM'S!! It was purchased locally here in OZ. I have a similar vintage natural aluminium case 61 R/C which my old UK mate Pete Tindall sent me as well. That engine is still unrun and sure looks a better build than the black case type.

>I've got one of the "light case" Merco 61's I hope to be
>running for the first time in the near future. Does anyone
>have any tips for running one of these brutes.

They sound really nice with a tongue muffler. The Merco is very similar to the old Super Tigre but just a bit more user friendly. They like a little more pitch in the prop and may make a tiny bit less power stock but John Wright knows some tricks to up the ponies if necessary. The one I'm currently flying has a .310 venturi with an air filter with the black screen insert and a Rev-Up 12-7 prop. I use the Thunderbolt R/C long plug and fuel with 10% nitro, 20% castor, 4% Klotz synthetic, a dash or two of white gas, and the rest methanol. Like many older engines they like lots of oil. You can run all castor but the ring will get goopy and may stick. Try my "special blend" if you want awesome motor runs. If you're wondering about the white gas, it says to add it right in the operating instructions that came from Merco. I tried it and liked it! I don't know why more people don't use the big Mercos. I guess it's just too easy.

Dave,
If your coming to VSC, please bring me a xerox copy of the Merco operating instructions. I wasn't aware of the white gas trick and I'd like to read about it. Or maybe you can post a copy here?
Happy Landings

>Dave,
>If your coming to VSC, please bring me a xerox copy of the
>Merco operating instructions. I wasn't aware of the white
>gas trick and I'd like to read about it. Or maybe you can
>post a copy here?
>Happy Landings

John,

I won't be making Tucson because I can only get away for one "biggie" this year and it's going to be Muncie. I'll see if I can dig up the instructions that mention adding "petrol" to the fuel mix.

>
I'll see if I can dig up the instructions that mention adding "petrol" to the fuel mix.
>
>Dave

I have two Merco 61's and would love to see the instructions for the Mercos. My engines have a single glo plug, black painted head, silver looking fins and a gray crankcase. Can anyone tell me what model Merco this is and how old? I don't think it would be referred to as a "light case" model. The weight with RC carbureator is 14 oz.

Thanks for any help and/or information.

MNel Peeples

I found the Operating Instructions and just need to arrange a scan so I can post. These particular instructions I think are for the Black Streak from Forest.

LAST EDITED ON Feb-12-04 AT 10:41 PM (CDT)
 
I have to say that all other factors aside, Dave have the absolute coolest sounding stunt run on the planet. When he flies the Merco on the big Super Chief, it just sounds right. Great growl and the plane is very cool. He keeps promising me plans, but as yet has not delivered.

OK, I'm kidding, Dave hasn't promised anything. But he should.

>>I've got one of the "light case" Merco 61's I hope to be
>>running for the first time in the near future. Does anyone
>>have any tips for running one of these brutes.
>
>They sound really nice with a tongue muffler. The Merco is
>very similar to the old Super Tigre but just a bit more user
>friendly. They like a little more pitch in the prop and may
>make a tiny bit less power stock but John Wright knows some
>tricks to up the ponies if necessary. The one I'm currently
>flying has a .310 venturi with an air filter with the black
>screen insert and a Rev-Up 12-7 prop. I use the Thunderbolt
>R/C long plug and fuel with 10% nitro, 20% castor, 4% Klotz
>synthetic, a dash or two of white gas, and the rest
>methanol. Like many older engines they like lots of oil. You
>can run all castor but the ring will get goopy and may
>stick. Try my "special blend" if you want awesome motor
>runs. If you're wondering about the white gas, it says to
>add it right in the operating instructions that came from
>Merco. I tried it and liked it! I don't know why more people
>don't use the big Mercos. I guess it's just too easy.
>
>Dave Royer

I have a super chief kit to build up and would like to use a Merco 61.
I have a light case twin plug variant, have you tried using twin plugs? I know that the 61SS utilised this head with only the rear plug position machined. Can you tell me which tongue muffler you use and how you fit it to the lugless case (Merco type wire hoop or adaptor to the central exhaust pillar?) and is it better than the standard merco silencer.
Thanks

>I have a super chief kit to build up and would like to use a
>Merco 61.
>I have a light case twin plug variant, have you tried using
>twin plugs? I know that the 61SS utilised this head with
>only the rear plug position machined.

I have not tried a twin plug version but I have talked to others who have and they say there is essentially no difference in the run.

>Can you tell me which tongue muffler you use and how you fit it to the lugless case (Merco type wire hoop or adaptor to the central exhaust pillar?) and is it better than the standard merco silencer.

I'm using an old SST tongue muffler for a Super Tigre .60 on my Super Chief because it was a bit nose heavy with the stock muffler. The stock muffler ran fine however and works well on both the Merco .61 and the ST.60. You can grind on the baffle some if there's too much back pressure for your setup. Also, Eric Rule (RSM) has tongue mufflers for the big Mercos I think. Most of my engines have threaded holes on the inside edges of the exhaust stack and both the stock and tongue mufflers mount using those. If your engine lacks this provision, perhaps one of Windy's strap-on tongue mufflers for the old Super Tigres would work. I've got one somewhere and if I can dig it up I'll see if it would work on one of my older Mercos that have just the center web mount in the exhaust. I don't know if Leonard carrys any strap-on mufflers for anything as large as the .61 but perhaps if he sees this he will confirm one way or another. John Wright may be a resource as well.

Elwyn et al - for a run down on Merco history, see Dave Day's web site <www.iroquois.free-online.co.uk> under Merco. It's as well to remember that Mercos have been made by various owners at various times, and quality has varied accordingly over the years.

Done that, its very useful. One thing not mentioned is the retaining screws for the cylinder assembly, I have a heavy case 49 which has 1/8 Whitworth screws but a later one of the same type has a different screw thread of the same daimeter (5BA,M3?). Do you know when they changed over an where you can get replacement screws.
Thanks.

All my Merco's ,both early (light case) and late (heavy case)have 5-40 screws. I got mine from Brown Nut& Bolt in Paramount CA. But most major cities probably have a nut & bolt vendor. Had to cut the 1 1/2" to 1 3/8 for the 61's. The 49 uses 1 1/4 but I didn't want to buy a box of 100 so I cut some more 1 1/2's. I also bought a box of 1/2 or 9/16 for the other 3 head screws and also use them in ST 60 & ST 46.

Dont forget that this is a Brit engine and I am pretty sure that the original thread was indead 1/8 Whitworth. That said if we look at the relative dimensions of these threads, - the 1/8 Whit is of course 1/8 inch diameter and has 40 threads per inch. The 5-40 UNC is also 1/8 diameter and guess what, it too has 40 threads per inch. The difference lies in the included angle of the thread, Whit is 55 degrees, UNC is 60 degrees. This means that (depending on the class of fit of the screws used) the UNC will give a slightly tighter fit in the relatively soft aluminum case - could be a different story into steel.

However these screws still will not fit the later 49 that I have which is definately fitted with screws of a finer pitch. I have not fully checked this out yet but 5BA(British Association)is .126 diameter but still only 43TPI and M3 is .118 diameter but close to 50TPI.

>All my Merco's ,both early (light case) and late (heavy
>case)have 5-40 screws. I got mine from Brown Nut& Bolt in
>Paramount CA. But most major cities probably have a nut &
>bolt vendor. Had to cut the 1 1/2" to 1 3/8 for the 61's.
>The 49 uses 1 1/4 but I didn't want to buy a box of 100 so I
>cut some more 1 1/2's. I also bought a box of 1/2 or 9/16
>for the other 3 head screws and also use them in ST 60 & ST
>46.

I've been going ga-ga trying to find a source of 5-40 screws (socket heads prefered) but I would be more likely to find rocking horse poo here in UK. I tried the UK division of Unbrako but was told that this is a 'non prefered size' and not available in UK! The very similar 1/8 inch Whitworth is listed as available here but vendors say it is not. Does anyone know a good mail order source on your side of the pond?
Thanks,

LAST EDITED ON Mar-23-04 AT 11:31 PM (CDT)
 
Mike,
Go to: http://www.microfasteners.com/catalog/products/SSCSCA.cfm
I just checked there and they are about $5.50 Americam dollars for a quanity of 100 of the 5-40 X 3/4 lg. socket head screw. They also come in 1/4, 3/8, 1/2, 5/8, 3/4, & 1.00 long and larger up to 2 in..

I've been going ga-ga trying to find a source of 5-40 screws (socket heads prefered) but I would be more likely to find rocking horse poo here in UK. I tried the UK division of Unbrako but was told that this is a 'non prefered size' and not available in UK! The very similar 1/8 inch Whitworth is listed as available here but vendors say it is not. Does anyone know a good mail order source on your side of the pond?
Thanks,

Mike Bennett

Mike,

It's a bit of a long shot, but try an RC car dealer who stocks parts for U.S.-produced cars, probably off-road numbers. I know for a fact 5-40s are used in some of the Losi cars, for example.

>Mike,
>Go to:
>http://www.microfasteners.com/catalog/products/SSCSCA.cfm
>I just checked there and they are about $5.50 Americam
>dollars for a quanity of 100 of the 5-40 X 3/4 lg. socket
>head screw. They also come in 1/4, 3/8, 1/2, 5/8, 3/4, &
>1.00 long and larger up to 2 in..

Thanks Greg, yes they are listed and they ship international, I'll give it a whirl.