Removing Lower Cowl On 1955 Mark 6

[Bill Matuscak]

I just got a Mark 6 (serial# 892918) for cheap and am attempting to remove the cowling. I've got it loose, but it looks like the whole power head has to be removed to get off the lower cowl. Any help would be appreciated. I'd like to do some cleaning and inspecting to see if the thing is worth saving.<br /> I want to get a service manual for this motor. Does anyone know of good rescources? Grubbs wants $50.00 which is about 3 times what the motor cost. Does Clymer or Seloc have them for the older motors?<br /> Thanks in advance.

 

[Chinewalker]

Re: Removing Lower Cowl On 1955 Mark 6

Yes, the powerhead has to come off to get the cowling off.<br /><br />What are you hoping to inspect with the cowling off? Check the compression, magneto components and fuel system first. If a problem turns up, then go ahead and pull stuff apart, but if it checks out healthy, there's no need to pull it apart. Listen for excess bearing noise that might indicate a problem internally.<br /><br />Those Mark 6s are ballsy little motors for their size and will easily plane off a small tin boat. The weakness is in the lower units, as they are prone to cracking due to water freezing inside. Keep an eye on your gearcase lube and make sure the tiny pinhole drain on the undeside of the gearcase bullet is free of debris.<br /><br />Try eBay for a manual. Older versions of the one Grubb's sells turn up from time to time...<br /><br />- Scott

 

[Chinewalker]

Re: Removing Lower Cowl On 1955 Mark 6

One other note - if you're like most of us with the Old Mercs bug, your Mark 6 won't be your last old Merc, so the $50 investment in the factory manual Grubb's has won't go to waste...<br />- Scott

 

[Bill Matuscak]

Re: Removing Lower Cowl On 1955 Mark 6

Thanks for the advice, but not really what I wanted to hear! I wanted to clean the accumulated sludge and gunk while I looked for a manual for the serious stuff. It could use a paint job too. Found an old mouse nest down by the carb. I want to pull the carb and clean it.<br /><br />The motor has good compression but no spark. The shifter works. There is a crack in the lower unit as you mentioned. Are used ones available, or is it possible to repair the crack with either welding or JB Weld?<br /><br />Bill

 

[Chinewalker]

Re: Removing Lower Cowl On 1955 Mark 6

Hi Bill,<br /> The lower units USUALLY crack around the trailing edge of the gearcase bullet. USUALLY they crack fairly cleanly right where the rear spanner nut lies. If yours has, then it is sometimes possible to clean off that cracked portion and reuse the housing as is. However, this involves a modification where you thin the rear carrier to allow the rear spanner nut to bite in new threads. How much you thin it depends on how much of the rear threads remain. If memory serves you should have about 1/4" to play with. It's not always possible, but it can be done on many of these. Make sure you leave enough of an air gap in there so that the water will have a place to go. That gap is in line with the intake holes in the housing and needs to be there so the motor will pump water.. If you do go this route, it's a good idea to tear the whole unit down and replace all the seals while you're at it. <br /><br />Looks like you're in for pulling the powerhead. Not really difficult, though. Be careful not to kink the neutral clutch cable, otherwise it becomes a real pain in the behind to feed back down. Pull it out and tape it up in a neat small coil.<br /><br />Having fun yet?<br /><br />- Scott

 

[Bill Matuscak]

Re: Removing Lower Cowl On 1955 Mark 6

The crack on mine is on the side of the lower unit above the gearcase bullet and below the cavitation plate. That's the only one I've seen so far but I will look closer when disassembly time comes.

 

[Chinewalker]

Re: Removing Lower Cowl On 1955 Mark 6

Hi Bill,<br /> Hmmm. That crack usually means bigger issues. They crack there when there is actually water inside the gearcase. Water in the gearcase can mean noisy bearings, pitted shafts, pitted gears, etc. Definitely worth an inspection. <br />- Scott