Fresh water? Go with Magnesium. Aluminum in a pinch.

 

For Inboards... There is a big on on the stern and one on each trim tab... Contact www.boatzincs.com for the best prices... BTW they are sponsor on this site...

 

The 340 Sundancer was offered with a variety of drives over the years it was produced.

You do not list your drive nor year.

Even if we knew your drive, say Bravo III, the answer would vary by year.

We need to know the year, drive and use (fresh or salt). A photo would be best.

Let’s say you have a 2003 340 with Bravo III drives and you boat in fresh water.

You would need two (one for each drive) of these kits
http://www.boatzincs.com/bravo2-3-mag-kit.html

You may or may not need anodes for the trim tabs. They tend to last longer.

I would also recommend you add an additional prop anode, again two, one for each drive.
http://www.boatzincs.com/MERProp-Nut-D-mag.html

Now let’s say you have a 2004 340 Sundancer with Bravo III drives. The kits area different, the now standard prop anode is different.

Its all different again if you have inboards.

So, in summary, we need more information to help you.

 

Mine has the obvious anodes on the tabs and the big transom anode. THen there are two hull anodes udner water close to the underwater exhaust outlets. They are right where the bonding system wires are connected in the bilge seemingly to the hull where the underwater exhaust ducts go through the hull.
there are also two shaft anodes on the prop shafts.

The zincs completely glazed over in the clean fresh water were in and no longer working I believe. I changed the tabs and transom anodes to magnesium last fall and won't worry about the others. You can again see the magnesiums working (eroding) and I probably need a set a year or so.