Merco 61 Twin Plug Strip Down

[Andy J]

Engine problem No 3!

 

Whilst looking for some parts that the borrowers  had taken and hidden away, came across my old Merco 61 which dates back to the early 60's. Engine was second hand when I purchased it as a youth and I certainly have not dismantled or changed the bearings over the last 60 years.  Engine has seen a lot of running in the 60's and 70's mainly in a super 60 but little since then. Last time I ran the engine I recall it leaked more fuel from the front bearing then it used.

 

Anyway given I now have a hub puller decided to strip the engine down.  All the screws came out without an issue so was able to remove out the piston and crank.  Front bearing came out easily as it had a step slightly larger then the crank bore so was able to push it out from the inside.  Problem I now have is how to get the rear bearing out as the crank casing is flush with the internal bore of the bearing so unable to get anything behind the bearing to force it out.  Tried several cycles of heating and using a tight fitting aluminium tube inside the bearing packed out with masking tape but can shift the bearing at all. Anybody got any ideas how to proceed.

[Martin Harris - Moderator]

I've yet to fail to remove a rear bearing after heating the crankcase in an oven and slapping it onto a block of wood.  Try 150 degrees C at first and if unsuccessful raise the temperature 10 degrees at a time until it lets go. The mass of the bearing in its suddenly stopping housing makes a very effective slide hammer!

[Martin McIntosh]

I recently did a bearing change on one of those for a friend. A heat gun was not enough but a blow torch freed it up. New bearings came from Model Fixings.

If it was leaking oil/drawing in air through the front housing then there may well be excess wear on it but not to worry if it runs OK. My mate`s is now as sweet as a nut and more powerful than I remember them to be.

[Rich Griff]

Yes, but make sure the gum and crud is cleaned out which may cause the momentum method not to work.

 

Cellulose thinners very good but petrol cheaper for cleaning, cheapo car plan aerosol carb cleaner good as well but a bit expensive......aerosol and soaking failed to get all the gooo/crud from the "void" involved with the rear bearing.

 

I heated mine in hot oil for about 25 seconds, when hot, removed, covered hand hold with rag and struck down squarely onto wood. The rear bearing came out first strike.

 

Be aware that although the rear cover area is flat and square ( and square too ), the exhaust area sticks out a bit, so strike down on the wood squarely, if you see what i mean.

 

Midel fixings have emailed, need to check finally then I will order from them Tuesday.

 

Need to check the front bearing outer has a seal/shield, should control c/case compression/depression/loss better.....so engine runs better.

 

Your front bearing an skf  with a brass/ bronze cage, 7 balls ?

 

Over.....

[Rich Griff]

Ps, I have a merco marine exploded view with part numbers, will try and post, dated 7/78....1978 ?

[Andy J]

Exploded view could prove useful Rich as unsure if there is a casket between the finned piston machining and the engine crank housing.

 

Manish your trick of a blow torch did the trick as gave up with the oven method when I got to 180C so the bearing is now out.  Just waiting for it to cool down before I confirm its size against what the Model fixings site declares for the single plug Merco 61.

 

As for gaskets has anyone had any success in using a low power laser cutter to produce these.  Will need to order some more gasket paper anyway as once again the borrowers have taken and hidden the odd pieces I had.  If anybody knows what thickness to use that would help.

 

As for cleaning the old gunk off the engine, cellulose thinners seems to be ineffective so have tried meths this morning but that does not seem to be doing much.

[Andy J]

Little confused as to the rear bearing size. Model fixings declares it as 12.7 28.57 6.35 for the single plug but does warn you that the twin plug version could be different.  Unfortunately my cheap micrometer gives slightly different readings 12.6 28.52 6.37. Has anyone any experience on Merco's as to the correct size bearings?

 

Just measured the crank shaft diam and that is 12.7 +- 0.01 so suspect what MF declare is correct and that my internal measurements using the micrometer inside gauge is prone to error.

 

One other point I noted is that the rear bearing has a shield on the front face was this correct? Front bearings had no shields fitted.

Edited May 24, 2021 by Andy Joyce

[Andy J]

12 hours ago, Rich Griff said:

Your front bearing an skf  with a brass/ bronze cage, 7 balls ?

 

No, my front bearing was made by Hoffmans but yes it does have 7 balls and a metal cage.  As mentioned there was no shield on the outer, so unclear if this is an original bearing or not.

Edited May 24, 2021 by Andy Joyce

[Martin Harris - Moderator]

I suspect model fixings are approximating imperial sizes.  Try measuring in inches and searching on Simply Bearings. 
 

1/2” x 1 1/8” x 1/4”

[Andy Stephenson]

I've seen a Mercos spitting out fuel from the front bearing so it would probably be best to replace it with a sealed one but remove the rear facing seal so it gets lubricated.

Edited May 24, 2021 by Andy Stephenson

[Andy J]

Well you could well be correct Martin as metric was not common in the UK in the 60's. Still measure my wood in imperial, but old habits will eventually die out just hope I have a few years left of using imperial.  Just to be certain on getting the correct size have ordered the rear bearing from MF and all the others including the OS FS-52 bearings from Simply Bearings.

 

Yes I have ordered a sealed bearing for the front Andy but suspect it could well spit out fuel due to wear on the casting. 

 

Not even sure the Merco will ever go in a model or be used. It was more along the lines of an experiment on taking engines apart given my recent experience with the RCV 58CD.

 

Still interested in any thoughts on cutting gaskets using a laser cutter and cleaning burnt on residue.  Do have some oven cleaner or is that way too harsh.

[Martin Harris - Moderator]

Loctite bearing fit will seal a loose front bearing.  I had one that had spun and dropped out even when stone cold that was cured this way.
 

Irvines, for example, often leaked in this area from new causing the engine to continue idling long after closing the throttle and a few drops on the periphery on reassembly would cure this. 

[Martin Harris - Moderator]

Cleaning casings?  People often recommend boiling them with a dishwasher tablet. 
 

Depends how bad/far you want to go. Vapour or bead blasting is the ultimate...

[Martin Harris - Moderator]

Never had any dealings with a laser cutter - but I have used the old cornflake packet, oily thumb, ball bearing method on more than one occasion. 

[Rich Griff]

Any numbers on the bearings, I needed a magnifying glass ?

 

Both cellulose and meths work well for me, as does petrol.

 

Suspect my engines have been busy running castor.

 

The magnum gp40 tiawanies engine was a bit more difficult to clean, the brown staining seemed to be really burnt on, a synthetic fuel maybe ?

 

Since the bearings are now out, maybe the "wonder" kitchen cleaners will shift it ?

 

Going to loft to get the info sheet now, will try and post picture after lunch.

 

Are your engine screws slotted or X head ?

[Rich Griff]

Rear  Cover gasket, a brown envelope perhaps ?

[Andy J]

Rich

Back bearing looks like its marked with three letters possibly BFH or EFH. Also LT? D.

[Denis Watkins]

1 hour ago, Martin Harris - Moderator said:

Cleaning casings?  People often recommend boiling them with a dishwasher tablet. 
 

Depends how bad/far you want to go. Vapour or bead blasting is the ultimate...

Also, to add to this list

Simmer the parts in antifreeze

 

[Martin Harris - Moderator]

Does this still work with modern antifreeze or do you need glycol?

[Rich Griff]

I have heard about the antifreeze trick but not tried that yet, may try on one of the Cox 049's when stripped down.

 

Pictures coming over now hopefully.....sheet dated 7/78...1978 or slightly later ....

 

Sheet says do not distribute the crank, use 3 in 1 to lightly lube.....

 

3 in 1 seems to gum up after a year or so, initial start up not good as 3 in 1 does not mix with glow fuel....model technics engine after run oil on its way with fresh fuel order, £93 4 gallons 2 after runs, straight castor, gn5, gn16 for the coxes

 

Will be enguiring about asp 45 new in box that will be going in a gangster when the time comes....hope this helps....

 

 

Edited May 24, 2021 by Rich Griff

[Denis Watkins]

22 minutes ago, Martin Harris - Moderator said:

Does this still work with modern antifreeze or do you need glycol?

Yes, this still works as modern antifreeze is just right for us

Namely, it is designed to operate in Aluminium engines

It does work a treat

As always, do not leave unattended as this potion will readily boil dry

Edited May 24, 2021 by Denis Watkins

[Rich Griff]

I will give that a try....on a Cox 049.

 

Neat, 50 percent with tap water ?

Edited May 24, 2021 by Rich Griff

[Andy J]

Well the engineers broth did semi work but dishwasher tablets did oxidize the castings so would not recommend it.

 

Whilst waiting for things to boil then noticed the front cone cylinder had hair line fractures so could explain why it leaked fuel from the front.

 

Then cleaning the piston I caught the ring with my paper rag and it snapped so would now say I have a bag of spares for anybody thinking of working on a Merco 61!

 

 

[Caveman]

Andy, if you look at the exploded view posted by Rich Griff you'll see that the tapered collet is meant to be split.

GDB

[Andy J]

All is not lost as see you can still buy replacement rings for £12 of ebay for the Merco. Guy selling them is over at Pitstone so not a great distance from me.

 

Yes was just going to mention that about the front collet but believe I can see other fractures on the item.