I found a lot of good info about props scattered about the site so I thought I would make a thread for all things prop.
I noticed this post from Mr. Christy:
Originally Posted by LChristy
During the recent sale of my boat the surveyor commented that the 14X14 prop that is class legal is the wrong prop for the boat. This has been confirmed by Bengt Johannson in discussions with Martec. With the current prop it is difficult to get the engine to 80% of max as encouraged by Yanmar. I believe this leads to carbon buildup in the cylinders. If the rings contract during the cold winter temps the carbon prevents them from returning to the cylinder walls. This can lead to cylinder damage. Happened to be about 10 years ago and had to have the engine rebuilt.
The J30 Class needs to look into this and see if a prop change is in order. Would help extend the life of your old engines.
Larry Christy DA KINE (Sabreline 42)
Just wondering if Bengt made any recommendations as to what the proper prop would be? I think I am facing either a prop rebuild or replacement as mine is getting pretty floppy in the blades and they are tending to get stuck closed much more often.
If I am facing a replacement, I might look at a kiwi-prop. My slip-mate put one on his Santana 30/30 and he really likes it. He says the three blades make a huge difference to vibration levels. Does anyone have any experience on the J/30?
Picked up a new 2-blade Gori last fall. Hope it performs well, Ill see in the spring.
My old Martec was in sad shape when I got the boat, and I had it rebulit. 4 seasons later it needs anouther rebuild and I figured I would try a higher quality prop.
One other note about the Martec's. I recently had mine rebuilt since it was quite loose. Apparently there are 3 different size bushings you can put in the prop when rebuilding - each time they have to go to the next size up.
When you get to the last size (which I have), that's it - no more rebuilds!
Rhapsody's prop was rebuilt by by sending back to Martec in 2009. The cost was ~ $230 and included drilling for over-sized pivot pin, weld buildup for blade stops, and machining back to original spec. It came back looking like a new prop.
So OK ... for background 1. photo of original pivot pin in drilled out hole
2. photo of pivot pin that depends on groves to hold in place
3. photo of cotter pins that hold the pivot pin in place note that there is only so much room to redrill before the cotter pins will not work. see top photo
Martec is quite reasonable. I bought a new Martec prop last year (to keep the integrity of the one design) and it really helped with vibration. As new props go, it's pretty cheap. Now I can reliably go backwards... bonus!
![[Linked Image from j30.us]](http://www.j30.us/images/Martec-Refurbished.jpg)
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![[Linked Image]](https://j30.us/ubbthreads/ubbthreads.php/ubb/download/Number/1080/filename/original%20pin.jpg)
![[Linked Image]](https://j30.us/ubbthreads/ubbthreads.php/ubb/download/Number/1081/filename/pin.jpg)
![[Linked Image]](https://j30.us/ubbthreads/ubbthreads.php/ubb/download/Number/1082/filename/cotters.jpg)
![[Linked Image]](https://j30.us/ubbthreads/ubbthreads.php/ubb/download/Number/1110/filename/photo.JPG)
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