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OEM engine bolts.. special coating???

C

centerline

Regular Contributor
on my 1975 mercury motor, the OEM bolts holding the engine together are NOT stainless steel, but they arent corroded or rusty either.... so what is the special coating that Mercury uses on their bolts to stave off the rust that seems to affect every other steel piece of hardware that is exposed to the marine environment?....
I know they WILL rust and corrode eventually, but they withstand for much longer than standard hardware bolts.

I would like to get some with the same type of coating for another project, without spending a fortune on OEM merc bolts.. Thanks
 
If coated then they are/At least the nuts are typically made of an copper alloy / brass with a chrome plating to the outside...Some bolts may be the same too.....But just know that aftermarket such as Sierra will say their part number replaces a Merc oem part number but in all actuality the nut is Stainless Steel.

For instance the nuts that hold on a Merc stern drive is OEM part number 11-859116 which the Material is Plastic polyamide locking insert with copper alloy nut while Sierra is SS as seen here, http://www.marineengine.com/newparts/part_details.php?pnum=SIE18-3721 vs oem description here, http://www.marineengine.com/newparts/part_details.php?pnum=MER11-859116

Nut and bolt info tip: Sometimes if you know the OEM part number, you can run the number within the following link / in the search area at the top and get some additional info regarding the nut or bolt in question, http://www.parttarget.com/5310-01-5...16.html/-7F98557F-EB5E-4F4E-BA8F-B4168296E67F
 
Just don't use stainless nuts on stainless bolts. Even with an anti-seize coating, they can seize on you. Nasty!

Jeff
 
Thanks centerline, A high alloy content stainless hardware is not magnetic,but does not have the tensile strength of a pure steel
 
fastjeff said:
Just don't use stainless nuts on stainless bolts. Even with an anti-seize coating, they can seize on you. Nasty!

Jeff
Click to expand...
correct... but if you use nickle antisieze, stainless on stainless will NEVER gall and seize.. until the nickle antiseize goes away..

seizing is cause by the heat stainless creates when it rubs together, and the nickle antiseize has a high molybdenum content (which is used as very slick, high temp lubricant) and has a heat rating of 1200 degrees, so it lubricates as well as protecting the stainless from heat damage.. No galling.
 
..."if you use nickle antisieze, stainless on stainless will NEVER gall and seize.. until the nickle antiseize goes away.."

And then they seize! I worked for a company that made cryogenic hardware, which means they had to use stainless exclusively (since carbon steel cracks at ultra low temperatures). We had to live with seized fasteners on a regular basis--and we KNEW how the best ways of preventing that.

Stainless on stainless is a time bomb.

Jeff
 
When you lubricate any threads the torque value is less than a dry thread is the only thing I can add. Without knowing your application we can only make educated guesses. Is it more cost effective to use OEM or chance using aftermarket is always a personal choice.
 
kimcrwbr1 said:
When you lubricate any threads the torque value is less than a dry thread.

Without knowing your application we can only make educated guesses.
Click to expand...

yes... this is important information that some dont realize.
there are two published standards for torque specs, one for clean "dry" nuts/bolts, and one for clean "lubricated with 30wt oil" nuts/bolts.... neverseize does NOT qualify as oil, as depending on its formulation it can be much slicker than 30wt oil...
 
No doubt Carl used cadmium plated steel bolts.----------------Did not believe in stainless even for driveshafts.-----------No problem in using harware store stailess bolts in your older fine Mercury motors.
 
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