Old Merc questions....Chinewalker???

[tmcalavy]

Just acquired an Merc Mark 7 Rocket, in passable shape. Some questions...what's the best way to clean/chase the threads on the crankshaft? Got the flywheel off and will have to redo the magneto, coils/etc, but the last owner buggered the top two or three threads. Time for a tap/die kit?
2nd question...the prop seems frozen on the prop shaft. Any tips for getting it off? Don't want to beat on it. Is the water pump/impeller behind the prop?
3rd questions...is an impact wrench the remedy for frozen nuts/bolts? Have two frozen on the recoil mech cover...now soaking with Kroil. Thanks in advance.

 

[Scaaty]

Re: Old Merc questions....Chinewalker???

Well, ya gotta be real careful when you go down with a Die so ya don't cross thread. Best bet is an adjustable Die holder with inserts, that crank in tight on the good threads, then chase them up.

Also, if the 2-3 are above the nut when on, just get a Dremel and grind them down

And you just need a thread chasing Die, not a cutting Die. Quality tool supply houses have them.

Also you can take a similar nut, hacksaw in half, then C-Clamp it on the shaft threads, then work its way up with some oil to lube...little ballpeen tap to resurrect the threads..clean up with a Thread File..
I probably have what you need in a Die (they aint cheap), if you can get the the OD, and TPI. (Threads per inch).

I can stuff it in a bubble mailer if you really need it..figure a couple bucks shipping, but I want them back of course!

Rest is Scotts territory...

 

[tmcalavy]

Re: Old Merc questions....Chinewalker???

Thanks Scaaty...I'll check here in town first and see if I can find it, after trying the nut/c-clamp process. It may come down to removing those damaged threads but we'll see. I think I know where the Chinewalker is this weekend...hope to make that aomci meet someday myself but it's 1,300+ miles one way.

 

[Scaaty]

Re: Old Merc questions....Chinewalker???

So thats where everybody went!!
If ya have a friendly local small machine shop in town, they might just be able to help out with lending ya something too..good luck

 

[tmcalavy]

Re: Old Merc questions....Chinewalker???

Chased the threads with a nut...but wound up just eliminating the top two threads. Now I can get the flywheel secured again. Also discovered how to drop the lower unit, but looks like the impeller is behind the accursed stuck prop. Guess I'll do the coils and fire it up in the barrel to see if there is any pump/impeller behind the stuck prop. If it runs I'll have to tackle the prop gently.

 

[Yepblaze]

Re: Old Merc questions....Chinewalker???

I might have suggested a big angle grinder and fugettabout the mushroomed end.

 

[Scaaty]

Re: Old Merc questions....Chinewalker???

I might have suggested a big angle grinder and fugettabout the mushroomed end.

Big not needed....4-4/12 would do...

 

[Chinewalker]

Re: Old Merc questions....Chinewalker???

Hi Tim,
The prop has, I think, a rubber clutch system inside it. I don't think the Mark 7s had the metal and fiber disc system used on the KG7s, etc. That said, I think you're up against some corrosion that only heat, lube and patience will resolve, unless you go ahead and cut it off. Hate to do that if it's a really nice prop.
An impact wrench is your best friend! I use mine all the time to pop bolts & screws loose, and I break fewer that way. Good, clean bits for it are key - old ones with rounded tips are useless.
And yes, as you discovered, the impeller is under a threaded cover in front of the prop...
- Scott

 

[CharlieB]

Re: Old Merc questions....Chinewalker???

Be very careful with the air impact guns.
Too strong a gun often breaks bolts/studs off.
I've had years of success using my 3/8 gun turned down just a bit and a torch.

I use a cutting torch tip as I can get LOTS of heat right where I want it in a with a quickness, then rattle it off with the air gun.

Lots of old salted drives have needed the torch to slightly 'blister' the alum to get it to let go of the bolt enough to turn it out.

Sand, paint, looks fine, and sure beats replacing casings.

 

[tmcalavy]

Re: Old Merc questions....Chinewalker???

Thanks for more info guys. Looks like I'm going to have to heat the prop as a first attempt...then cut it off if that doesn't work. Don't want to bugger the prop shaft trying to pull/beat the prop off. That said, is the Mark 7 prop unique...will another prop from a similar era Merc fit the Mark 7? I plan to pick up an impact wrench today...hope that does the trick loosening a couple of recoil cover bolts that have been soaking in penetrating oil.

 

[tmcalavy]

Re: Old Merc questions....Chinewalker???

Bump.

 

[tmcalavy]

Re: Old Merc questions....Chinewalker???

Cool beans! Had a good short afternoon in the shop today. I put an impact driver on the stubborn recoil fasteners and got them free, pulled the recoil out and lubed it, unsnarled a loose coil of rope and reinstalled the tank/recoil on the Mark 7. Did a proper compression test and I have 80 lbs. on both cylinders. Now I'll have to find a couple of coils, rebuild the mag plate, fix two drill holes in the tank and see if it will run in the barrel. Then consider the stuck prop.