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re-sizing propeller

  • Paul Hayes
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08 Dec 2023 22:01 #1 by Paul Hayes
Replied by Paul Hayes on topic re-sizing propeller
Are you assuming that in 34 years you still have the original prop that Linsen fitted, or are you going from the information you have seen stamped on the boss?

Just a thought.

I too would suggest checking the tachometer reading. Audio tachometer Apps for mobile phones are available, I've compared one with my mechanical tachometer and it was accurate within acceptable tolerance.

Paul Hayes 

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  • Stephen Thompson
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08 Dec 2023 09:59 #2 by Stephen Thompson
Replied by Stephen Thompson on topic re-sizing propeller
Diameter and pitch are increased. I have shaft diameter and assumed the taper and keyway were standard?? I will get them measured before buying a new prop

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  • Balliol Fowden
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08 Dec 2023 09:38 #3 by Balliol Fowden
Replied by Balliol Fowden on topic re-sizing propeller
Do Linssen advise that just the pitch needs to be larger, or the diameter as well?

I might be teaching you to suck eggs here but if you are sourcing another propeller you will need to know the shaft taper details: the exact taper dimensions, length of prop boss and keyway size. Can they tell you that as well? If not you will need to first remove the prop to measure the vital statistics.

Hence my suggestion to repair and re-pitch the existing prop since you know it will fit straight back on.

Balliol.

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  • Stephen Thompson
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07 Dec 2023 23:00 #4 by Stephen Thompson
Replied by Stephen Thompson on topic re-sizing propeller
Thanks for the post.
I am pretty sure the tachometer is close enough
I contacted Linssen and even though my boat is 34 years old they were able to review their records and advise me that the correct propeller is larger with a bigger pitch so I am now trying to source one
Cheers
Steve

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  • Richard Pentreath
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06 Dec 2023 20:18 #5 by Richard Pentreath
Replied by Richard Pentreath on topic re-sizing propeller
After acquiring my own vessel in 2018, i became convinced that its 28" prop was grossly under-pitched for the output of its 160hp Deutz engine, as it was too easy to overspeed. Then I discussed the problem with a guy I met on the Sharpness Canal who'd worked as a Perkins service representative. He said "have you checked the calibration of the engine RPM gauge?" "...er no, but I surely will", I said, and then learned how cheap and easy it was to get a digital readout device that you point at the flywheel.

And so I found out that the rpm gauge had likely never been calibrated at build - and was mis-reading by a factor of almost two! Once corrected and singing off the correct hymn-sheet, the gauge revealed my prop-matching to be about perfect.

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  • John Frazer
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29 Nov 2023 15:35 #6 by John Frazer
Replied by John Frazer on topic re-sizing propeller
There is a guy in Bruges who does prop fettling, don't have his name to hand, but Thijs at the boatyard in Diksmuide will know him.
(I doubt that he would advise you, you would have to tell him what alteration you need.)

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  • Balliol Fowden
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29 Nov 2023 14:05 #7 by Balliol Fowden
Replied by Balliol Fowden on topic re-sizing propeller
It should be possible to repair your existing prop and at the same time tweak a bit more pitch into it. It is amazing what a skilled firm can do. The most respected name for this is Jooren’s in Dordrecht, but there will be others. 

Extra pitch may increase any tendency to paddle wheel (“prop walk”). That will depend a bit on your existing pitch/diameter ratio.

Extra pitch will load the engine more at lower revs (at the expense of reduced peak revs) but whether this will reduce the smoke problem would remain to be seen. My guess is that it would improve matters. Joorens are likely to be familiar with the issue, and presumably you have talked to Linssen.

Balliol.

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  • Judy Evans
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29 Nov 2023 11:14 #8 by Judy Evans
Replied by Judy Evans on topic re-sizing propeller
Stephen,

Apologies - my memory is not what it was! 

We did replace our propellor when we first got her but unfortunately all the paperwork is on the boat - in France - so Im afraid I can’t check, sorry!

Judy

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  • Stephen Thompson
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29 Nov 2023 10:25 #9 by Stephen Thompson
Replied by Stephen Thompson on topic re-sizing propeller
Hi Judy
It is Steve here from Bethany Leigh. We have communicated before about our identical boats and yes our engine smokes a lot and requires an Italian decoke every few days. Therefore I think that we may as well enjoy some fuel saving by running a bigger propeller at lower revs.  You dont happen to know what size prop you have on?

By the way we travelled 1000km in our first season ending up in Diksmude Belgium. It took us a while to sort out the boat to set it up how we want and it was worth the effort as we love it

Cheers
Steve

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  • Judy Evans
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29 Nov 2023 10:04 #10 by Judy Evans
Replied by Judy Evans on topic re-sizing propeller
Can I ask a tangential question of you?

We also have a 1989 Linssen 35SE. Our engine is a Volvo TAMD41A. Is yours the same or a B? I ask, because running at low revs as we do, given the speed limits on inland waterways, means that the engine smokes dreadfully due to it being under-worked for its size. We have tried many solutions (including the “Italian Job” 😜) plus additives. Apparently Volvo realised the problem and modified the design from the B series upwards. They no longer offer a retrofit solution for the likes of us 😏

Does your engine smoke?

Judy Evans
MV Mon Amie

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