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Engine basics => Engine set up tips => Topic started by: Glen Wearden on April 29, 2009, 03:11:35 PM
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I have a Merco 61, dual plug that I'm setting up initially for RC, but it might morph into a CL application later on. My question has to do with whether, or not, both plugs need to be lit for starting, or will one suffice? Seems like I read somewhere that it is only necessary to light one, and the other starts to glow from the effects of combustion. Any dual-plug experts out there? Thanks in advance.
Glen Wearden
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Glen, That's whet I've always heard also..
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Hi guys,
I'm using several of the Merco's with the twin plugs. I've been told that just to light one plug and the other will help. I don't believe it does, I have installed a dead plug in one hole and run the engine. The engine ran great, didn't change a thing but in a good plug and guess what the same. I've been told bye some of the best that the second plug will help, I just don't believe it does, just me, Gary (Its a good place to store a spare plug?)
I really love my Merco's, ( 49's and 61) I believe they're some of the best engines you can use. They don't seem to be as strong as some but everyone of mine has a great run. I use mostly the lite case merco's, I have some of the square bottom ones and they don't seem to run as nice and smooth as the lite case engine. Some will tell you the 49 is to heavy but man they really have a great run. There quite a few different merco engines in the 49 and 61 models. It seem like the ones with the single plug and dual rings have more power than the dual plug single ring engines.
For the money you pay for them, can beat them. I bought mine off of e-bay and was lucky that Mr. Frank Bowman rebuild them for me. Frank did a great job on each engine and everytime I start one I just say Thank You Frank, Gary
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I appreciate your answers, guys. My 61 is vintage late 60's. It has a black head and bright silver fins, with a 4 bolt backplate, and a single ring. I had to get a Kavan carb for it because the needle valve on the old one was damaged and I couldn't find a replacement. I'm looking forward to using the engine. Thanks again. Glen
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Glen;
It is only necessary to put the igniter to one plug. Once started the other will light by itself. I run a Saito 1.82 Twin on the SDR and it has 4 plugs. I need only to light one on each cylinder.
"Billy G" D>K
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The only twin plug engine I've actually run is my son's OS H-80 and putting power to the second plug once it's running makes no difference to the revs. It's always been held that the second plug automatically begins to glow once the engine is running and the only way I can think of to find out if it really does is to check the resistance of the coil between not running and running. If it glows then presumably the resistance would increase (if my very limited knowledge of things electrical is correct :)).
As for Mercos, I have 3 of the larger ones (and 2 of the .35's). One is a Merco 49 Black Streak (two plugs), one is a Mk2 .61 (light case, two plugs and brand new) and the latest is a Mk1 .49 which was given to me by a wonderful old guy near Nashville. His spare brand new 49 crankcase arrived yesterday. The story behind this engine is that many years ago (and it must have been 1962) he was in a London hobby shop having a cup of tea with the owner when a Merco rep came in to say that the new Merco 49 was now available. My friend immediately said he'd have one and went back the next day to pick up his engine. So it's one of the first (possibly even the first) Merco .49's ever sold commercially, still has an extraordinary compression seal and starts first flick every time :).
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Glen - Also thanks from me for asking that question. I've had a .49 sitting for several years that I just kind of work around as I didn't really know how to start it properly. Now I don't have a reason not to use it !!!!!!!
Dalton H
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To further bore everyone with the story behind my Merco, In 1971 ( I think), I bought the engne to run in a DeBolt Jenny trainer that I built. I also built a Heathkit 4 channel RC rig to put in it. Amazingly, everything worked, except the pilot. After several take-offs, but no successful landings, the plane was trash, so I put the radio and engine away. I subsequently used the radio in a couple of other planes, but as an effect of several moves (Army), the engine went missing and I gave it up for lost for over 30 years. Then, a while back while I was looking through some boxes for a slide projector, I found the Merco and a Torp 35 ( still haven't found the projector, but maybe St. Anthony will help me with that, too). Ramblings...........................Glen
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dMerco .49 was my first Carrier engine and most succesful. Loaned to a guy for a scale plane. He passed away several years ago and don't know what happened to the Merco. Also I have a Fox .50 control in my engine stash somewhere. While moving to the new shop I thought I would find it. It has hid itself somewhere in my stash. DOC Holliday
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Ran her on the stand, today. Third flip start; good, rich 4 cycle for about a minute, then leaned out to a rich 2 cycle at the top end; back down to slow idle for a few seconds; transition back to top end was smooth for a rich high-speed needle setting. I ran Powermaster 10/22 (11/11), and the engine seems to like it. The engine had a butterfly baffle on the exhaust, but I was able to fit it with a header and muffler from a ST G51 (bulky and heavy), which seemed seemed to be compatible with the engine, as it didn't seem to overheat. I'm happier than a pig in a big bucket of clabber!!!
Glen
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The intended purpose for twin plugs in the Mercos was better idling for the radio boys, not a power booster. Having siad that, in due course they reverted to single plug. Better plugs? Lower production costs? Who knows. This seems to indicate the twin plug Merco could be good for a classic 2-4 run.