Other Galvanic corrosion Stainless steel fastners in cast aluminum

[96superjet]

I know that stainless steel bolts are used exclusively in Yamaha motors and bolt directly into aluminum castings such as cylinders, cases, etc... and apparently there is no concern about galvanic corrosion. So when it comes to the pump section (I'm working with a 155 at the moment), why are the 7" long pump bolts made of aluminum? I suspect it has to do with the pump being exposed to water and potentially salt with higher levels of frequency.

So my real question is... if I wanted to tap the front wear ring holes where the bolt typically goes through and then threads into that big pump tunnel (I'm speaking of how 155s bolt up on coaches) and thread a large 7" long 3/8" diameter stainless steal bolt into the freshly tapped holes, would I experience galvanic corrosion problems (BTW, I'm almost 100% fresh water). Or for that matter, are there any other unforeseen problems I might experience?

 

[Proformance1]

My 155 mag bolts a galvanized steel not aluminum. I have never seen the OEM aluminum bolts.

 

[96superjet]

As I look close at this bolt it does appear to have some type of galvanized finish. I ran the threads through a die to clean the redish/orange thread locker off them and noticed the metal appeared REALLY soft. Therefore I assumed they were aluminum.

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[naticen]

I don't think Yamaha engines use stainless fasteners. Kawis do. I think pump stuff is stainless on both though.

I'm all salt and lube everything with grease and never have stuck fasteners. I know a lot of freshwater guys like loctite though. Galvanic corrosion is a necessary evil you just gotta deal with.

 

[augustaf]

Galvanic corrosion occurs between dissimilar metals in the presence of moisture, unless....... you block it by using grease, anti- seize or threadlocker on the threads. Using threadlocker would certainly be indicated if the op uses the described ss fasteners. They will certainly stretch/elongate more compared to that fancy alloy Yam uses.

 

[kevbo]

Use a lot of teflon pipe thread sealant everywhere steel touches aluminum.

 

[air blair]

Those long bolts are just galvanized steel. Prevents rust. I have weighed the options of tapping into hull(shoe) not worth the time or work involved for what it is. Imo fill and tap the where ring or epoxy in a nut, heli coil, timecert, rivnut, something along those lines.

 

[Retarded Timing]

They are zinc plated and if you ran them through a die you might want to replace them if it stripped the zinc off. The zinc acts as the sacrificial anode. If you stripped it off, the bolt will corrode rapidly. Yamaha engine bolts are just chrome plated steel.

 

[air blair]

They are zinc plated and if you ran them through a die you might want to replace them if it stripped the zinc off. The zinc acts as the sacrificial anode. If you stripped it off, the bolt will corrode rapidly. Yamaha engine bolts are just chrome plated steel.

Yep, thats the reason as soon as you thread it into something or put a wrench on that chrome bolt it starts its cancer in the salt and/or condensation. Anti-sieze is a beautiful thing for oem pump bolts

 

[tor*p*do]

They are zinc plated and if you ran them through a die you might want to replace them if it stripped the zinc off. The zinc acts as the sacrificial anode. If you stripped it off, the bolt will corrode rapidly. Yamaha engine bolts are just chrome plated steel.

or just spray them with this stuff
works great, used it on my trailer and it is really holding up well