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No thrust - intermittent

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Liam Brooke View Drop Down
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Post Options Post Options   Quote Liam Brooke Quote  Post ReplyReply Direct Link To This Post Topic: No thrust - intermittent
    Posted: 04 Feb 2013 at 1:46pm
Dear Fellow Contessa Owners,

My boat (Tantris 1977) seems to have thrust / prop issue. Sometimes she wont get above 2knts even with full throttle. Then other times, 3-5knts isnt a problem.

It is potentially a dirty bottom, but then even with a clean bottom she is intermittent. I think it is something to do with the folding prop not 'popping' out properly as if I play around with the throttle, she will sometimes give me wildly differing boat speeds. 

It is disconcerting, as I need a little more than 2 knts forwards.. Any suggestions welcome.

Best

Liam Brooke
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moongirl View Drop Down
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Post Options Post Options   Quote moongirl Quote  Post ReplyReply Direct Link To This Post Posted: 04 Feb 2013 at 7:41pm
Liam
Your local resident 'expert' CO32 man here!
Sounds very much like the prop needs a bit of grease. I presume it's a DARGLOW. There is a point on the back of the hub where you can fit an angled grease nipple - DARGLOW sell them if you didn't get one with the boat.
Regular greasing at least once a year - until grease comes out around the blade roots. Without greasing, as well as 'sticking' you will get gear wear which will alter the pitch & reduce drive.
Lastly an anode on the prop (2 set screws into back of hub) is essential. DARGLOW do a flat one that fits between the prop & leading edge of rudder.
Regards
COLIN
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Keny View Drop Down
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Post Options Post Options   Quote Keny Quote  Post ReplyReply Direct Link To This Post Posted: 05 Feb 2013 at 2:57pm
It could be a slipping clutch. Check to see if your propshaft is slowing down. You should get 7 knots easilly with a reasonably clean hull & 18-20bhp engine.
Ken
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Liam Brooke View Drop Down
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Post Options Post Options   Quote Liam Brooke Quote  Post ReplyReply Direct Link To This Post Posted: 10 Jun 2013 at 12:05pm
Well chaps,

Thanks for the feedback. I lifted her out, cleaned and antifouled. She is looking very pretty now.

I also greased her prop and replaced the anode. 

She will now do 4-5 knts under power.

Sorted.

Best

Liam
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moongirl View Drop Down
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Post Options Post Options   Quote moongirl Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jun 2013 at 6:43am
Liam
You should get more than 4 to 5 knots. It's possible that although the prop is now behaving ie 'unfurling' there may have been some wear which has altered the pitch.
At 2500 rpm you should get something like 6.5 knots.

Regards
COLIN
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George Isted View Drop Down
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Post Options Post Options   Quote George Isted Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jun 2013 at 10:51am
Hi Colin,
I hate to disagree with you but I don't think I have ever achieved 6.5kts under engine alone, but I would like to hear that is possible with a larger engine or bigger/coarser pitch prop.  I have a 13" darglow (one of the earlier JF Props but has been back to have it's pitch adjusted) and at cruising RPM of Circa 2600 we get about 5.5 kts through the water.  With a clean bottom and prop I can get her just over 6kts at 3200rpm but don't like running the engine that fast due to the noise.  My engine is a 2GM.
 
It would be good info for all if skippers can post this data so we can get a picture of what speed through the water is achievable with a particular HP engine, type of prop, clean hull in flat water, I'll start, hopefully others will post....
 
Concerto, Yanmar 2GM, 13x9 Darglow, 2600rpm = 5.5kts, 3200rpm 6kts.
George Isted
www.solentboatbutler.co.uk
Contessa 32 "Concerto"
Co32 Class Measurer and ex Class Captain.
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Keny View Drop Down
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Post Options Post Options   Quote Keny Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jun 2013 at 1:39pm
George - I'm adding to your survey.
Liam doesn't actually say what engine he has but I have a Betamarine 18bhp with a low drag Campbell high efficiency fixed 13" sail prop. Feathering props. can't be as efficient because they have to be flat shaped in order to feather properly.
We conservatively do 6.7 knots on the impeller speedo and 7 knots on the GPS one in these conditions at 3200 rpm.
keny
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Keny View Drop Down
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Post Options Post Options   Quote Keny Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jun 2013 at 1:56pm
Sorry guys - my prop. is a 12"/7" & not 13" as stated previously.
keny
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moongirl View Drop Down
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Post Options Post Options   Quote moongirl Quote  Post ReplyReply Direct Link To This Post Posted: 11 Jun 2013 at 10:14pm
Keny
As others have said engine power probably determines what speed you can get.
This weekend & for the approach to the RTI we had 6.5 k on with some tidal assistance. Muscadet has a 3 cylr Beta & DARGLOW 
My experience when sailing Polar Star (DARGLOW + Yanmar 3GM) was that we could get at least 6 k initially but over time the gears in the prop wore until the prop was more like an egg beater. The prop had to be re- built.
COLIN
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Alan Dixon View Drop Down
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Post Options Post Options   Quote Alan Dixon Quote  Post ReplyReply Direct Link To This Post Posted: 15 Jun 2013 at 11:58am
Charlotte has a Vetus 25hp, with a fixed 14 x 9 three blade prop I can just get 7 knots with a clean bottom and 3100 rpm, the max it will rev too, cruising 5 to 5.5 knots at 2000 rpm, and sipping under 2ltrs per hour.
Alan Dixon "Charlotte"
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