Need info on a 1971 Merc 800 driveshaft

[Moody Blue]

Planning on doing a rebuild on a lower unit (metal fragments in gear oil when drained) and starting to look for parts.

Existing driveshaft has quite a bit of corrosion around the waterpump and seal areas and want to replace it. Anyone know what years (p/n would be awesome ) are compatible with the early 70's 4 cyls long shaft?

I think this is a mild steel shaft and later years used stainless.

 

[achris]

Re: Need info on a 1971 Merc 800 driveshaft

Hi Moody,

As I don't have the serial number for your engine I can only have an estimate at the parts groups.
The original part number for your shaft is either 45-47434 or 45-59116A1, and unfortunately both of those numbers are No Longer Available, and neither supersede to any later part. That would mean later shafts will not fit...

Best I can suggest is you take the shaft to a machine shop specializing in shaft reclaim.

Chris.....

 

[crem1]

Re: Need info on a 1971 Merc 800 driveshaft

Check out websites for driveshafts, i.e e-bay or get some more info from

http://store.eastcoastmarineservice.com/Default.asp

Americans are breathing down our necks

 

[Moody Blue]

Re: Need info on a 1971 Merc 800 driveshaft

S/N of the motor is 3146583 but no way of knowing if the LU is original or not. I have two other complete L/U of the same vintage (early 70's) but all of them have badly corroded driveshafts.

I'm interested in this driveshaft reclaim process. Is this a common procedure, and where would I look to have it done? General machine shop or small engine repair shop ?

Have also read somewhere about a sleeve that can be installed over the damaged area. What is involved in that approach?

 

[achris]

Re: Need info on a 1971 Merc 800 driveshaft

S/N of the motor is 3146583 but no way of knowing if the LU is original or not. I have two other complete L/U of the same vintage (early 70's) but all of them have badly corroded driveshafts.

I'm interested in this driveshaft reclaim process. Is this a common procedure, and where would I look to have it done? General machine shop or small engine repair shop ?

I found the shop I use by asking around. What they do is to 'spray' molten metal at the shaft while spinning it, then machine it back down to the original size. Lots of surface pep beforehand of course.

Have also read somewhere about a sleeve that can be installed over the damaged area. What is involved in that approach?

They're called a speedie-sleeve, made by Chicago-Rawhide. Read about them on SKF's website HERE. Depends on where you need to fit the sleeve as to the success...

Chris........

 

[Laddies]

Re: Need info on a 1971 Merc 800 driveshaft

We use a local hydraulic shop it's the same process that they use to hard face pitted cyl shafts

 

[Moody Blue]

Re: Need info on a 1971 Merc 800 driveshaft

Great info, thanks much.

Roughly what is the cost of repairing the shaft? I can buy new old stock for about $300 but getting the existing one repaired for less would be a great alternative. There is a good hydraulics house nearby.

Guess there is no possibility of using the newer S/S shafts in the older lower units?

Has anyone used the speedi sleeve to repair the shaft in the areas of the waterpump seals?

 

[Moody Blue]

Re: Need info on a 1971 Merc 800 driveshaft

Anyone have experience with the speedi sleeves on driveshafts?

Laddies or Achris (or anyone else), what should I expect to pay to have the shaft repaired?

 

[Laddies]

Re: Need info on a 1971 Merc 800 driveshaft

Speedi sleeves work great if you can find one long enough to cover both seal marks. We pay about $70 to $90 for hard facing depending on the job.

 

[emckelvy]

Re: Need info on a 1971 Merc 800 driveshaft

Depending on the extent of the damage you find when you disassemble the gearcase, you may be better off just picking up a good used lower unit. An excellent time to upgrade to a later-style with stainless in the pump area.

Check on eBay or your local Craigslist, you'll likely find something useable.

It'd be a good idea to stick to the 2.3:1 gear ratio found in these 66 C.I. Fours, the "underdrive" gears are better matched to these motors' HP/Torque curve than would be the 2:1 gearbox found on most Inline Sixes.

The only fitment issue you're likely to find with a later-style unit is lack of a groove for the driveshaft O-ring (where the driveshaft engages the crankshaft splines). This is because the later models use a metal O-ring carrier assy pressed into the end of the crank. This takes the place of an O-ring on the driveshaft.

An easy enough fix, just grind a groove in the driveshaft, using the location of the old lower unit's O-ring groove as a guide. I've done this before using a cutoff wheel chucked-up in an electric drill motor, it doesn't take long at all to grind a proper groove.

Any 66 C.I. motor of 85, 80, and 75 HP flavor will have the correct 2.3:1 gears.

The fitment is identical between all of the above. Stainless or stainless-clad driveshafts appeared somewhere around '76 or so. In '79 the gearcase was redesigned with swept-back skeg and other nice features, these are an excellent upgrade for an older motor.

Here's one currently listed on eBay that fits the bill quite nicely and is relatively inexpensive at $199 plus shipping:

http://cgi.ebay.com/ebaymotors/Mercury-75-HP-Lower-Unit-1980s-20-Shaft_W0QQitemZ320500475224

A lot easier to bolt up a good lower than tearing the old one apart, replacing very expensive innards & having to re-shim the whole mess. Something about the Law of Diminishing Returns I reckon!

HTH.........ed