Forums, Engine, Gearbox, Stern Gear, etc, No thrust - intermittent

Liam Brooke at 04/02/2013 13:46:56
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
07712423907

moongirl at 04/02/2013 19:41:09
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

Keny at 05/02/2013 14:57:30
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

Liam Brooke at 10/06/2013 12:05:59
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

moongirl at 11/06/2013 06:43:32
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

George Isted at 11/06/2013 10:51:43
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, 13×9 Darglow, 2600rpm = 5.5kts, 3200rpm 6kts.

Keny at 11/06/2013 13:39:10
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

Keny at 11/06/2013 13:56:50
Sorry guys – my prop. is a 12"/7" & not 13" as stated previously.
keny

moongirl at 11/06/2013 22:14:13
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.

Alan Dixon at 15/06/2013 11:58:57
Charlotte has a Vetus 25hp, with a fixed 14 × 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.

Richard Ritchie at 18/06/2013 13:46:45
Badger of Baltimore has a Yanmar 2GM20 driving a two bladed oversize prop: 15×12 inch. (The skeg cut out has been enlarged.
This gives 6 knots optimistically on a clean bottom and no chop. Guess at 2500 rpm. (I have no rev counter.)
Down to 4.5 knots and reduced revs if a very slimey bottom/prop.
Normally cruise at about 5 knots, at about 2litre/hr of fuel.

waratah912 at 16/07/2013 10:04:42
For the record, and anyone with a Volvo 2002 with a similar problem.
We had a period where you could engage forward but got no acceleration, engine stayed at idle and would sometimes cut out. This was intermittent, and resulted in some interesting moments negotiating the lock at Island Harbour!
Solution was a £4 spring washer which holds the engine end throttle advance lever in place on the shaft. Previous washer had worn and allowed the arm to wander around and also snag the engine stop which is on the same shaft.

Poppy787 at 22/10/2014 09:46:28
Thanks, for this. We too had a couple of incidents. One of the Suffolk coast, wind died engine on and no response from the engine, head into engine box to make sure all cables were secure suddenly forward drive no more problems for the rest of the trip. The second incident was more serious going astern in the marina I engaged forward drive to take the way off the boat; again no response from the engine result collision with another craft damage to both boats and a broken wrist. Several engineers inspected the drive train on Poppy and no one could repeat the symptoms, their suggestion the gear box was sticking; although this failed to explain why the engine sometimes remained at idol when in forward gear. Given the engine and gear box are, as far as we know, are the original Volvo Penta 2002 fitted in 1985 it was decided to replace both engine and gearbox. It has proved to be a very expensive spring washer, perhaps the potential for a serious accident to be caused by this problem should encourage anyone with an elderly Penta to check said washer.