Merco 61

I know the Rustlers are back in a new config at RSM, but I was just given an old R/C version, with the square bottom case, twin plug head (It's a deep hemi, but has TONS of compression).

Does anyone here know if these are the same as the C/L version, timing wise? Also, how does the front crank thrust washer come off? Is it threaded like some of the K&B or is it pressed in?

This one has a rather large gap (almost 1/8th") between the thrust washer and the front bearing. I think someone had it apart, and didn't get it back together quite right. The backplate was also loose, but when I tighten it, the conrod-crank pin rubs terribly on the backplate. It has what looks like a factory gasket, although it's thin as wax paper.

Also, reccomendations on a starting size for a venturi would be helpful. Going to play with it in my test bed ship, an overweight Magnum. If it can pull that, it can pull anything!!!!

I don't have any misgivings about this being up to snuff with modern engines, I already have those in my serious stunters. I'm just looking to see if this is worth ressurecting and having a little fun with.

Your engine does sound like it has been taken apart. I would be concerned about the rear bearing. Either it isn't seated properly, or it is the wrong bearing and slightly too thick. This would cause the crank shaft to be set back a little and be the cause of its hitting the back plate.

As to the venturi size, you would go roughly the same as on an ST 60. If this engine uses a true venturi (with the needle off to the side) then somewhere in the .187 to .199 range would be the place to start. If it uses a restrictor type venturi with the needle passing through the venturi, then with an ST (.155) size needle, use about a .310 to .320 opening.

Yeah Len, me too.

If I could get it apart it would help, but I don't want to cram a gear puller on the front washer and find out it's threaded or something. Still no bites from anyone who's worked on these?

The oxymoron of the situation is that gap at the front behind the thrust washer, and yet I can't tighten the backplate either. I just looked at the RSM add for the new RM 61, and it's hard to tell from the picture, but it looks like the thrust washer is away from the case too. I would think it's a dirt collector or place for junk to enter the front ball bearing if thats true.

In a more likely scenario, I wonder if the front washer is keyed, and they've jammed it on crooked, thus it doesn't pull the crankshaft far enough forward when I put on a prop.

Any one out there got a clue on this?
EricV

Eric, Tom Dixon sold Merco stunt engines for quite some time. His Merco 61's always seemed to run well, and I'm sure he can help with info and service advice on these engines.

I have 3 - 2 never been run, Merco 61's.

They all have quite a considerable space between the motor housing and the spinner/prop back plate. I measured the gap and it is 3/64" of an inch ( average between the three ). There is a thrust washer there as well but it seems to serve no purpose. Looking at the motors it appears the back plate is held in place with a split tapered collet. Never had any occassion to take on apart.

Big old bruts of motors. Nice 2-4.

Ken Clapson

Hi Evicv,
John Wright here. I'm the only one I know of who runs Merco's. I have one in my Magnum. It was shown on the cover of Stunt News on the warbirds cover. I'm the Messerschmidt 109 with the yellow nase and tail. I have the earlier lighter crankcase on mine but the innards are identical. I also use the two plug head although I have the single which I intend to try someday.
The thrust washer is a press fit cone, so heat it up and the gear puller should take it off easy. I have never had a problem with the crank rubbing the backplate.
On mine, I square off the intake port on the crankcase and that picks up the power a bit. It gives a good stunt run either way.
I have never seen a difference in the timeing of the R/C and U/C version. But I have done two other mods to mine. First I had it bored out to approx .64. That helps the power. Second, notice that the Merco has a conventional sleeve, but the cooling fins are separate from the crankcase. I took .008 off the fins to lower the timeing from 137 exhaust to 134 exhaust. It doesn't give more power but I run lower rpm now, about 8200 rpm and it turns a 12.5-5.5 3B Mejulik prop nicely. Before I had to run a 12" 3B and it didn't have the raw power.
Hope yours works out OK.
John

John, I'm crushed - I've been running Mercos for about 5 years now. My Super Chief started out with a .49 and after a couple seasons went to the .61. Both basically stock engines are flip and fly, use the same amount and type fuel, and prop which make major trim changes unnecessary. They both do a beautiful classic 4-2-4 stunt run. I love them both and settled on the .61 'cause I like the little extra grunt and it's about a quarter of an ounce lighter. I highly recommend the big Merco to anyone who is looking for simplicity and user friendliness. John gets more performance with his mods but I think they work pretty well stock too.

Dave,
Don't be crushed, I love my stock Merco's as much as my modified's. For the uninitiated, YES, they have a wonderful 2-4 break right out of the box and are easy to set up and run. Real good quality for the most part, with bushed rod and even bushed piston.
I just recently picked up a nice Light case Merco 49. I am anxious to fly it but I'm tied up with the Enya 60 right now.
John

Well... It all sounds pretty up beat. Guess I'll tear it down, make sure nothing obvious is out of whack from the last person who touched it, put new gaskets in and go for it.

A buddy of mine pointed out that the ring looked new, and I'm now wondering if a bearing was also replaced. If so, it may be a little thicker, hence the back plate rubs. If that's the case, a simple fix is to get rid of the paper-thin gasket that they had on the backplate, and use one of my sheets of that thick perfect brand gasket material that I still have left. (I know, I'll be carefull with the asbestos) or I could mill the backplate a touch. It really doesn't rub by much, the perfect stuff may even be too thick. We'll see.

Thanks,
EricV