Aluminum bolts?

[reelfishin]

I just got done salvaging a complete Merc 120 drive and motor, it's about the fourth one I've removed for future use and I was wondering why they use aluminum bolts on the two lowest positions on the gimble housing through the hull? one has a rounded anode attached and the other is plain, but so far, every one has had aluminum bolts.

Any reason for this? I would think that anything would be a better choice than aluminum for this location, even bronze or stainless. The other 4 through bolts are steel or SS.

 

[Bondo]

Re: Aluminum bolts?

Ayuh,....

I believe they're there for the Continuity,+ Corrosion protection.....

 

[reelfishin]

Re: Aluminum bolts?

Ayuh,....

I believe they're there for the Continuity,+ Corrosion protection.....

Everyone that I've removed has been badly corroded and nearly broken.
They were heavily pitted where in the middle where they contacted the transom wood. I've also seen aluminum bolts used as the upper two bolts on outboards, I've never trusted them, I've seen too many too badly pitted with salt corrosion to ever put a new set back in.

 

[rob85546]

Re: Aluminum bolts?

When I bought my boat and took it to the lake the first time, it was taking on more water than I thought it should.. Got the boat the home and had the wife spray the outside around the outdrive with a hose, while I looked around inside with a flashlight.. Found water coming in from where them 2 bottom bolts are. took them out and they were all corroded..found some on ebay for like 12 bucks.. no more problems...

Funny thing is in the paperwork I got from the guy who I bought the boat from, he had taken it to a marine dealer because it was taking on water, and they re-plugged some holes where the old swim plateform was..... I found it , but a marine dealer couldnt>>??

 

[Bondo]

Re: Aluminum bolts?

I've never trusted them, I've seen too many too badly pitted with salt corrosion to ever put a new set back in.

Ayuh,....

I guess that means,..
You'd rather see your outdrive Rot off the back of your boat instead,..??

Corrosion Is going to happen, especially in Saltwater,.....

I'd, personally rather see it somewhere Other than the actual Outdrive......

 

[Fishermark]

Re: Aluminum bolts?

In the words of the great Bondo - Ayuh...

That's why they put the little zinc caps on the ends .... they corrode instead of the bolt and outdrive. Just replace the end cap zincs occasionally and you should be fine.

 

[reelfishin]

Re: Aluminum bolts?

Ayuh,....

I guess that means,..
You'd rather see your outdrive Rot off the back of your boat instead,..??

Corrosion Is going to happen, especially in Saltwater,.....

I'd, personally rather see it somewhere Other than the actual Outdrive......

What's wrong with stainless bolts and zincs on the end of those just the same. The outdrive also has several anodes as well. I see the aluminum bolts as a leak potential. I pulled one set out that were only installed for a few years, in fresh water 90% of the time. They were corroded to about 1/8" in the center. The zinc caps were like new. I would think the loss of clamping pressure there, combined with a large leak would be far worse than controlling corrosion.