I have one given to me free, can anyone tell about them, venturi size etc.
thanks
Dwayne

The Merco 61 is an excellent old style ringed engine. Think ST V 60 stunt engine and you are there. It has been claimed that the ST 60 was a knock off of the Merco 61, with some justification. Ignore the dual plug head, it was really an RC gimmick. I believe that only one plug lights up and that is the one you power up, or so I am informed by more knowledgeable people.
 In my experience just about any way you would run an ST 60 will equally apply to the Merco. They are a very underrated engine and will give excellent performance. they don't shake as much as the ST 60 and apart from the inevitable ring problems on occasion (Just like the ST 60 and 46!). It will give you sterling stunt service.

Andrew.

Echo ,



flogged pictures to illustrate std C/L intake  . Flower Pot - ish , Trumpet - ish Bore . 49s shown . Mine was .275



one for the 61 is .295 , but I'd have to check figures . Run In / loosened off , the 49 hauled two kilo / 72 Oz.
Four Strokeing , on 15% & 20 % Nitro Fox Fuel ( 27% Oil ) on a 12 x 6 wood . Didnt like a tight ( tounge ) muffler
as the needle got to touchy . The big S T silent muffler gave no power loss compared to a open exhaust .

But the SOUND on the open exhaust was ' way cool ' . Vicious Maserati / tuned Bonneville / big block open headers at idle , ish .  
Depite factory advice that its not a ' nitro ' engine  . Mine was 1972ish , Got a 61 same series to get over the lost the Merco Blues .  

Right , the book fell out today ; the 49 stock C/L intakes 7.75 mm bore , so the other , in the 61 , is 7.95 mm . spraybars 4.05 mm dia.

The Merco 61 is an excellent old style ringed engine. Think ST V 60 stunt engine and you are there. It has been claimed that the ST 60 was a knock off of the Merco 61, with some justification. Ignore the dual plug head, it was really an RC gimmick. I believe that only one plug lights up and that is the one you power up, or so I am informed by more knowledgeable people.
 In my experience just about any way you would run an ST 60 will equally apply to the Merco. They are a very underrated engine and will give excellent performance. they don't shake as much as the ST 60 and apart from the inevitable ring problems on occasion (Just like the ST 60 and 46!). It will give you sterling stunt service.

     Agreed that the Merco 61 in general was an excellent stunt motor, a "poor mans ST60" back in the day. I though it might run better than an ST60 in the cases I saw.  One thing that it was noted for was using FAR less fuel for the same prop/speed than the ST. One advantage it had for me was that if I used it, I wouldn't get inundated with advice from "ST60 Experts".

   I never flew my Merco 61, but I have at least one somewhere in my massive stack of stuff. I really ought to go through that stuff and start giving away or selling it.

     Brett

   I picked up an older 2 plug head Merco .61   well used .. so I had it reringed ,etc ,  it never had the power of the "newer" single plug .61SS  I have 3 of the newer models from 1990 or so. They are quite powerful. Now if only someone can help me with a rear bearing...............  Funny my Olympus is going to have a Merco .61 in it also  .     
                        John

G'day. Andrew and Bill have more or less said it all. The purpose of the twin plugs was to aid idling in the R/C mode. The test report shown is for the original light case version, which many prefer for stunt.
Enjoy.

  I think the very last ones were made for target drones, so I wouldn't expect them to be designed for a long life! If anyone knows anything more about the target drone engines, I would be interested if they can share their knowledge. Andrew.

Hi Andrew. The Drone Mercos ceased to be made after the "Cold War" ended and the military ceased ordering them. Other Mercos continued for a time after this. The Drone 61's would have any or all of the following features :-

No sandblasting of the castings.
No bushings in the conrod.
No bushings in the gudgeon pin piston bosses.
Exhaust bosses for attaching silencer undrilled.
Plain head, no fins.
Possibly a simplified carb, - not sure about this.

Quite a few of these appeared in "our" market after the military stopped ordering.