Merc Engine Anodes

[Fireman431]

I have two 2001 Merc 7.4L (454) MPI engines. Backed up by B/W Velvet Drives. They have roughly 375 hours on each. No issues, run flawlessly, yadda, yadda, yadda. The boat is kept in central Florida in brackish water all of the time. Trim tab, rudder, and shaft zincs usually last about 16-18 months.

My problem is that I cannot find any anodes on the engines to replace. I have followed all of the incoming raw water lines and all I find are brass plugs and stainless bolts. I looked in the exploded view of the repair manuals for the closed water cooling, raw water cooling, intake, engine block, etc and nothing even mentions zincs or anodes. I also can't find any on the transmissions!

Is it possible that these drive trains are bonded to the bar zinc on the aft hull or am I just blantently missing something?

Any help (esp. diagrams or pics) would be greatly appreciated.

Larry

P.S. No obvious signs of corrosion. So far...

 

[Don S]

Re: Merc Engine Anodes

I know you don't have any anodes in the engine block or the transmission. If the heat exchanger and oil coolers are OEM, then no anodes there either.
Should be all bonded to the outdrive anodes and/or Merchathode.

 

[Fireman431]

Re: Merc Engine Anodes

Thanks, Don.

That makes me feel better.

 

[TilliamWe]

Re: Merc Engine Anodes

Where is there brackish water in Central Florida?

 

[Fireman431]

Re: Merc Engine Anodes

St. Johns River.

Head water are fresh south of Melbourne. The river flows North, heads East at Jacksonville and meets the Atlantic at the port of Jacksonville. It also meets up with Intercoastal Waterway there.

The water is salt in Jax but becomes more fresh as you head South on the St. Johns. It never truly is fresh water, though.

 

[TilliamWe]

Re: Merc Engine Anodes

St. Johns River.

It never truly is fresh water, though.

Sure it is. It might be a little brown, (tannic acid, I believe) but it's fresh along the way before Jacksonville. I've been in it several times.
Good luck with your anode hunt.

 

[Fireman431]

Re: Merc Engine Anodes

A little brown? It's a lotta brown. It looks like a lake full of Iced Tea!

We dipped a salinity strip in it a few years ago, just north of Lake Monroe, and it came back at just under 2%. Mostly fresh, a little salty, and always brown....ugh.

 

[TilliamWe]

Re: Merc Engine Anodes

A little brown? It's a lotta brown. It looks like a lake full of Iced Tea!

Yep, I got used to that real fast on the Winter Haven Chain of Lakes!

 

[dubs283]

Re: Merc Engine Anodes

most inboard setups have bonding wires for corrosion protection

you will see green 10 ga wire that will be connected to various components and attached to a bonding buss