CDI prop

[Ed Tamara]

Hi Gordon here I go again with a question about propellers.I've got a Yanmar 2GM20 and I saw advertised in a magazine a prop geared towards this tipe of engine; I have to back my boat in my slip and I have problems once in a while and this prop enhances the performance in reverse minimizing the sideways movement.It is supposed to be made of a plastic and the pitch increases due to centrifugal force by flattening the blade by flexing them due to it's revolutions. To me it sounds OK but I don't know about a SS shaft, saly water and urethane.This props are advertised in the back pages of SAIL and some other mags.

 

[Mark Waggoner]

I HAD a CDI

My 28.5 had a CDI prop when I bought it 3 years ago. It had already been on the boat for probably 3 years before that. It worked great. Unfortunately, a month ago I seemed to lose a lot of speed and had a lot of vibration. I thought I might have fouled something so I had the yard do a quick haul. All that was left of the CDI was about 2" of one blade. It's probably amazing that it got me out to the bay and back at least 3 times since I noticed the trouble. I have no idea what shattered it. The previous owner said he put it on because he would rather shatter a prop than twist a shaft. I didn't really think much about it though. By luck, I had the old bronze one on board when I pulled the boat so we stuck it on. Today I took it out for a real test and found that I actually gained some speed and had a little less vibration than I had before. I don't reverse that much, but it seemed adequate today with no discernable difference. I'm not sure what to think about the CDI claims. Before I had anything to compare it to, I was satisfied. Now, I'm satisfied with the original prop.

 

[Gordon Torresen]

CDI prop?

The S/S shaft, salt water, urethane and a bronze hub are all acceptable. Some of the other things are a little iffy. Flattening a blade usually means reducing pitch, flexing leads to fatigue failure. I have never been a great fan of anything CDI so I think it best to see what the users say.

 

[Ed Tamara]

Thank you both Mark and Gordon:I think you just gave me the answer I wanted, I'll continue with my bronze prop and I'll have it repitched.Thanks AgainEd

 

[Fred]

No CDI

ED: I saw the discussion regarding the CDI prop and was curious on your decision to re-pitch. From an ealier forum I understand that you have a 2GM in your H27 ... I did the same mod 11 months ago and agree that it's a good move. What will you re-pitch to? I have a 13x10, 3 blade and can rev to 3700 under load so I think I'm under pitched and/or should have a 14" prop. Your thoughts please ... thanks. Fred fkobashi@ieee.org

 

[Ed Tamara]

repitch

Hi Fred:I currently have a 14"x10 2 blade and I can rev it to 3500 rpm it is OK if I'm not in a "nose wind" then I have to motorsail her out of there, so I think I'll increase the pitch a little bit, but my problem is in reverse, I have to back up to my slip for a good 50 meters and even though I have the hang of it whenever I get a sideway wind I start going all over the place, I was hoping that the CDI would increase my efficency in reverse. I also had a 3 blade13and replaced it with a 2 blade and my sailing speed has increased a good 1/2 knot Good Luck Ed