Mercury 650 - missing piece?

[ShoestringMariner]

Hey guys, I just discovered that my “new to me” motor seems to be missing a plate or something. The bolt is hanging there loose.

Can any of you Merc guys help me out here? I’m hoping I’m not missing something serious or hard to find...

forgive my newbisms. I’ve only had experience using small 50’s outboards.

EDIT, photo coming - too large to upload

 

[ShoestringMariner]

[No message]

 

[racerone]

Sacrificial anode / trim tab.----Most shops would have it in stock.----Do not paint this part !

 

[GA_Boater]

What Racer said. The part looks like item #75;

 

[hardwater fisherman]

It looks something like this. And GA_Boater beat me to it.

 

[ShoestringMariner]

Great, thanks guys.
What does this do, is it some sort of grounding device?

EDIT, I looked it up

could this missing piece have contributed to heavy pitting on the lower outer part of my transom? Pitted at or below the waterline

 

[racerone]

It is a sacrificial anode, and a trim tab to help with steering " feel "

 

[GA_Boater]

The anode helps save aluminum parts of the motor from disintegrating due to stray electrical current. The sacrificial part means it erodes instead of the AL motor parts. So yes, it can help with the pitting.

Depending on where you boat, it is very important for long life of the motor. Also the fin helps offset prop torque so the boat tracks straight.

 

[racerone]

Galvanic corrosion is involved----Look into " nobility table of metals.---Google ----noble metals----To see what it is about.

 

[GA_Boater]

I just remembered your SS thread. The missing anode didn't cause the transom and chine pitting, but it didn't help.

 

[ShoestringMariner]

Great, thanks guys