Let's discuss this sacrficial anode design issue, will save you DIY guys a few bucks if you want to, otherwise key out of this thread now.
Each anode weights a certain amount, let's say as an example - 1/2 lb. When the engine manufacturer designs the protection, he decides how much weight to use and where to locate them. Since engines are placed on boats with a wide range of usage, season length, trailered or not, shore power or not, salinity level of water, docks with poor or good grounding systems, the amount of anode used up per season will vary widely.
So, in your particular boat, in the exact slip you moor, the anodes can fret away faster than the same exact boat/engine on the other side of the marina.
All that matters, is that at the end of the season, you have not used up the weight and should have some remaining say 25% minimum of the original weight. If you have 75% of the original weight intact, then you can go another season on the same anode. My figures are conservative.
And it's not unusual for some of the anodes to fret away faster than others.
When I first bought my Sailfish, the Drive anode was used up per season, I added trim tab anodes, and now the drive anode goes two seasons easily.
Marinas and mechanics can't be bothered with evaluating anodes so they just replace them - heck, you are paying the bill - right? Why would they care what the added cost means to you ? (ie. "If you can't pay, you shouldn't be playing" nonsense)
The weight is what matters so it's hard to tell w/o removing it until you have some experience like I do, to be able to eyeball them. Yamaha did a good job with the huge anode on the brackets - and is very easy for me to eyeball, just have to lay on my back and look up. Poke it with a screwdriver to see if it is solid, so ahead.
Under no circumstance, should you ever allow any particular anode to be totally used up during the season because there is no metal left to sacrifice itself, and if anodes fret away faster than usual, investigate - something is wrong. Don't ignore this, you will pay big time later.
On the Yamaha trim tab anode if lost during the season don't sweat it, unless you keep your lower unit in the water down while moored vs. tilted up. However, on say an I/O, the anodes on the rams, if lost or totally fret away during the season, better get it replaced as soon as practical because the I/O is always underwater.
If the DIY guys have any specific anode questions - ask, and if you feel more comfortable PMing me, please do.
