Prop Zinc Question

[Rick & Karen]

Good Evening Everyone,

Karen and I took Kolo Iki out to 12 feet of crystal clear water this afternoon to replace the prop zinc. Although we only launched her seven months ago, the zinc was almost totally destroyed. For most of that time she was slipped at the Waikiki Yacht Club and from what I have read here and on other sites, some marinas tend to disolve zincs at a fairly rapid rate. Now that the boat is docked in a residential area without any shore power hookups, I am hoping that we will get a year or more of corrosion protection between replacements.

Today was the first time I have ever tried to replace any kind of sacrificial zinc and I found that the T-handle 1/4" hex wrench I was using made it more difficult because of the length of the wrench and the location of the rudder. Karen was doing a fine job functioning like the operating tech she used to be and helping by handing things to me and moving the rudder at my request in an attempt to get a better angle to work from. Although I could not take a full turn with the wrench, I was able to make small movements and eventually the holding screw was loose enough that I could back it out by hand. The zinc came right off when I pulled on it and then I took a wire brush to the prop nut and cleaned it up a bit (although it was in great shape) in preparation for the replacement (size C) zinc.

Karen assembled the parts of the new zinc and handed it down to me and I applied it over the nut and tightened the screw by hand as far as I could. That was the easy part, now I was back to making very small tightening movements of the screw with the hex wrench. Eventually the screw was as tight as I could make it and the prop was starting to turn with the screw when I tried to tighten it further. There was still a small bit of back and forth movement after I was done and when we drove the boat back to the dock I detected a funny noise coming from the rear of the boat and what I sensed might have been a previously unnoticed vibration. My guess is that the loose zinc was interferring with the prop balance.

I think what I need is a 90 degree bend Allen wrench that will allow me to apply more torque to the screw while I am holding the prop with my other hand. I checked with a very knowledgable salesmen at West Marine when I got back and he said that it was not unusual to have to hold onto the prop tightly while adding more leverage to the screw. I wanted to ask the assembled brain trust at this sight for their experience and wisdom when it comes to replacing the prop zinc on the R-21 tug or any other boat with an inboard engine. I realize that many of you keep your tugs on a trailer, but in this case, that shouldn't make much of a difference to the procedure. Any help you can give me would be appreciated.

On a different, but related topic, I noticed that Andrew's PDF file for zinc sizes lists a shoe zinc for the R-21EC tugs. My tug did not have a shoe zinc when I purchased it and I was wondering if this was something that was added to 2008 and later tugs. Looking forward to your responses.

Mahalo,

Rick

 

[Andrew Custis]

I am not sure when the shoe zinc was added but I thought we have been putting it on much longer than that. I typically see about 6 months on the prop zinc and a year might be wishful thinking because when they deteriorate they tend to slip off the end of the brass coupling. I would be sure to check it every 6 months at least.

To make removing the zinc easier turn the rudder all the way in one direction and use a 90 degree allen wrench. Seems to be the easiest.

 

[Rick & Karen]

Hi Andrew,

Thanks for the response, I attended a Diesel in a Day class today taught by the local Yanmar Dealer and I stopped at Home Depot on the way home and bought a set of long handled 90 degree hex wrenches. When I got to the house Karen and I and her visiting cousin fired up the boat and went just offshore. I donned my fins and mask and jumped in and it took me all of about thirty seconds to cinch down the holding screw. Amazing how the right tool always makes the job easier 🙂

As to the shoe zinc, I will look for the mounting hole for it the next time I am in the water. I had a build up of barnacles on the prop and the rudder and it kind of hid the condition of the zincs. After having the prop cleaned I am much more aware of the need to stay on top that area of the boat. I am in the water almost every week so I will keep a much closer eye on things in the future. The rest of the boat bottom is very clean and I want to see how long I can keep it in the water before having it hauled.

One thing that was commented on today in the class I attended and by another marine electrician working on our boat is the fact that the engine cannot be isolated from the electrical system. The engine will start with the battery switch in the OFF position. Something tells me this is not how Ranger designed the boat. The number one battery has a cable connected directly to the battery and the position of the Battery Selector Switch does not make any difference when cranking the engine. Any light you could shed on that would be appreciated.

Aloha,

Rick

 

[rt11002003]

Rick,

Our 2009 R-21 EC doesn't even have a selector switch (isolation switch?) for the engine, unless one considers the key operated switch on the engine panel a selector/isolation switch.

I do have two other isolation switches. One is under the helm and isolates the house power. The other is under the v-berth on the starboard side; I believe it's for the thruster. I checked it once, but have forgotten what circuit (s) it controls.

I was confused when I first bought the tug because all of my boats in the past had three position selector switches. This system seems to work OK, the only drawback I see is the inability to use the house battery for starting, if needed. Maybe a set of jumper cables would suffice.

Gene

 

[Andrew Custis]

You have answered the question. The key switch is considered to be the on/off switch for the engine. It is wired in through a isolator and relay which will charge both batteries underway. I agree with Gene on this. The only drawback is not having a 1+2 switch to paralell to two batteries together if the engine battery dies. The only reason we didn't do this is because we dont have anything going to the engine start battery other then the engine starter itself.