R21-EC propeller questions

[greenghost45]

Hello;
My 2006 R21EC has a Yanmar YM30. I noticed that I had lost the propeller zinc last time out; boat is on the trailer except when being used. While inspecting the prop, which is in good shape, I noticed there was about 1/32" of lash. That is, the prop can be rotated about that much by hand, before the driveshaft engages. Is this normal or do I need to tighten the prop nut or pull the prop and inspect the keyway? The cotter key is in place and the prop nut appears to be tight and the cutless bearing seems fine.

Thanks for your advice!

 

[lproulx]

Your prop nut must be at least a little loose. It may have allowed the small slack you notice in rotation to beat up the key, which may be made of brass. Take the prop off and have a look. Probably a new key and good tight nut will fix the problem you inquired about.

Second bit of free advice/suggestion. I have had it with those conical zincs that go on the prop nut. They always fall off. I have been buying a plain collar type zinc and trimming it down to fit between the prop hub and the hull. It's kind of hard to cut one down (I actually use a lathe) but can be done with a hack saw/sawzall or whatever. I have been thinking of having a spacer made that would allow the prop shaft to stick out of the hull a little more and make room for an un-modified collar type zinc.

Larry

 

[BB marine]

I'm going to give different advise. The prop should not move at all on the prop shaft once installed. The prop shaft has a machined taper. The prop must be drawn on to this taper to be properly installed. The shaft key is a secondary devise installed to fix the prop to the shaft in the event the torque is great enough to allow the prop to move on the shaft. When a prop is installed onto the shaft the correct method of installation is to install the prop on the shaft with out the key. Push the prop onto the shaft taper as far as it will go. Mark the shaft where the prop stops. Now remove the prop and look at the taper and confirm that the prop advanced all the way on to the taper. Now fit the key into the keyway and repeat prop installation. The prop with the key installed in the keyway should advance to the same location as it did without the key installed. If it does not, the key is not fit correctly. There is a high spot on the key or in the shaft or prop hub keyway. Inspect all components clean or file any high spots and refit the prop again confirming full prop advancement onto the prop shaft. Once you get a good fit. Tighten the prop nut "good and tight" I usually use a torque wrench and set it at 100ftlbs. There really is not a torque spec for "good and tight" but 100 ft lbs has worked for me.

Installing a collar anode forward of the prop should be done with caution. The cutlass bearing needs to have a good flow of water to lubricate it. You want to have at least 3/4" between the cutlass bearing and the prop or an anode to maintain proper water flow for lubricated the bearing.. My C26 only had 7/8" between the prop hub and the cutlass bearing . Installing any type of collar anode between the prop and the shaft log/ cutlass bearing would not really be a good idea.

 

[lproulx]

If the shaft packing drips properly it is all the evidence you need that the cutlass bearing is getting sufficient water.

Larry

 

[BB marine]

If the shaft packing drips properly it is all the evidence you need that the cutlass bearing is getting sufficient water.

Larry

Larry you are correct. As long as the packing is leaking all the time when cruising. Many times the packing will leak at the dock but when cruising, it will not get enough water up the shaft with an anode blocking it and the cutlass is not lubricated properly . If this works for you that is great but it goes against most recommendations given by cutlass bearing manufactures, surveyors, and boat builders. If a prop nut anode is not used on a keel extension or keel shaft log designed boat it is recommended to use a shaft grounding brush and attach it to a hull anode. On a open strut designed inboard the recommendation is to install the shaft split ring anode a minimum of 15 " forward of the strut to allow enough water flow through the cutlass bearing. The only lubrication the bearing gets is water.

If this works for you, great, continue using the cut down shaft collar anode. My thoughts are I would not recommend it unless I made all the proper checks and confirmed good water flow through the bearing to protect the bearing and shaft integrity.

 

[mikey]

Is it a good idea to use locktite on the c 28 prop nut?