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plastic prop

3K views 7 replies 3 participants last post by  grey99 
#1 ·
I have a two blade fixed plastic (ok, composite) prop from CDI. It''s on an 11hp inboard diesel on a 28 ft boat. It got nailed badly with barnacles and so I am pulling it to tidy it up over the winter. It just got me to wondering what people think of CDI props and composite props in general? I have a spare two blade bronze prop I could use, but I am concerned about it''s weight. Any opinions? Thanks!
 
#3 ·
I purchased a CDI plastic prop for my Atomic 4 and have been VERY happy with it for 4 or 5 seasons. My top end increased by .5 knot or more and I can start and stop faster as it seems to dig in better. It now has a couple of nicks in it, but seems to be holding up just fine. I would buy another rather than switch back to my old bronze prop.
One concern has to be the strength of the prop. CDI claims if you hit the plastic blade hard enough to break it, the blow would bend a bronze prop putting it out of balance. CDI claims that their prop will work better with one blade than a bent bronze prop. I bought that explanation - besides, if you hit bottom w/a sailboat prop, you usually have other worries, like where did your keel go.
Regarding the use of your bronze prop: Assuming you bought your boat used, I am wondering if your spare bronze prop came with the boat, in which case I would guess the old owner replaced w/plastic and was happy with that move or he would have put the bronze back on. If the prop is not from your boat, you do need to look into it''s suitability. The wrong prop can really have a negative effect on your performance and I would be concerned it could lead to overtaxing your engine causing overheating and other problems.
 
#5 ·
The prop really does seem to dig in more then regular props, and goes very well in reverse. When the performance backed off towards the end of the season, I worried but then observed the heavy barnacle growth when the boat came out for the season so the performance loss seemed plausible. It has a small nick in an edge, but CDI tells me I can fix it with a dab of Bondo and careful sanding and then recommending painting it with their special antifouling paint. That seems like a plan. The big old bronze prop came with the boat, I found it at the bottom of a locker and concur that the previous owner was probably pretty pleased with the CDI. I think if I were doing a lot of serious offshore cruising I would have some strength concerns, but as a knockabout coastal cruiser I have no worries. I was just curious about other peoples opinions -- it seems like a good deal to me, relatively cheap, with an apparent difference in performance (but then I was the one taken in by the Eco-Horn so my opinions are sometimes suspect). Anyone out there ever broken a urethane prop?
 
#7 ·
Regarding the question on pitch - I do not know the pitch as CDI markets this prop as being designed for the Atomic 4. As far as I know they only have one prop for the engine.

Repairs: mine has some knicks and I have not bothered with repair nor have I noticed a difference - but now you have me thinking.
 
#8 ·
Hi--

Well, I''m going to pull it this weekend and try this bondo repair. I''ll post the results of that little experiment. The nick is small, but hey why not make it beautiful before painting? The thing I have to try to avoid is oversanding, the nick is in an edge and I want the repaired section to stay true. Anyway, thanks for the opinions, I think I''ll stick with the CDI.
 
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