Propeller noise/vibrations?

[royaldo]

Hi,

I have never owned a boat or sailed before I bought this old Jupiter 33 from 1975. Motor is a Volvo Penta TAMD70B and the transmission is an old hydraulic Borg Warner/velvet drive.

My question is how much noise/vibrations from the propeller is to be expected in a old boat like this? The cutlass bearing does not seem to have much play in it.







My question is how much noise/vibrations from the propeller is to be expected in a old boat like this? The aft of the hull is made of 12-15 mm massive glassfiber, so I guess there is not much soundproofing in the hull by itself.

Noise/vibration is most apparent in the aft cabin, which can be heard in the last part of this video. The boat is going 8 knots at 1400 rpm (700 rpm on the propeller) in the video.

https://youtu.be/JQzXEQvbkKo

 

[oldgit]

from the photos there appears to be very little clearance between blade tips and hull.
Pretty sure there is rule of thumb between tip and hull to allow water displaced by propeller to flow clear and not be impeded by bottom of boat.
If prop wash is directly hitting hull perhaps its resonating. ?
Is the engine mounted directly to bearers or via rubber bushes.

 

[Tranona]

Yes, that prop looks too large diameter for the boat and is too close to the hull. The minimum clearance iss 10% of the diameter - ideally 15%. So, that looks like at least 20" diameter so 2" clearance. Photos can be deceptive but does look a lot less. The flat bottom of the hull will not help if it is prop wash related. Noise and vibration can come from other sources such as out of true shaft, engine movement from worn mounts etc which may manifest itself in a different place from the source.

 

[JerryC]

Hi and welcome to the forum. The cutlass bearing shouldn't have ANY play in it at all. If you can wobble the prop by the slightest amount you need to replace the bearing. It will only get worse over time and it's not too difficult or costly to replace. For a 1975 boat, if it hasn't been done before, it prob needs to be done now.

 

[Neil_Y]

Hi and welcome to the forum. The cutlass bearing shouldn't have ANY play in it at all. If you can wobble the prop by the slightest amount you need to replace the bearing. It will only get worse over time and it's not too difficult or costly to replace. For a 1975 boat, if it hasn't been done before, it prob needs to be done now.

Not strictly true, better to measure the clearance and play.

All shaft bearings need a degree of clearance/play as the shaft runs on a water film when turning, which is allowed for in the running clearance. So there should be some play which you can measure with a feeler guage at the top of the shaft where it enters the bearing. At rest there should be a gap between shaft and bearing at the top.

As an example on a 2" shaft a new bearing has a clearance/play of 0.27mm, change the bearing when it gets to around 1.25mm. The running clearance is not fixed and depends on the size and wall thickness of the bearing.

 

[Portofino]

View attachment 72269

View attachment 72270

To help reference appropriate distance between the tips and hull .

 

[oldgit]

due to age suspect not original prop and probably not the size the boat started with either.
Possibly the prop was cheap,available and it fitted !
If you can live with it, leave well alone and at some future point if prop needs attention get it cut down and re pitched to compensate.
Would look out on ebay for suitable 4 blade, which it may have had to start with.
3 blade might have been fitted in misguided attempt to go faster .

 

[royaldo]

Thanks for the answers.

Distance from prop to hull might be a little bigger than the first pictures seem to show. The picture below might show it a bit better.



Cutlass bearing was checked by a professional and he didnt think it was due to replacement yet.

 

[royaldo]

due to age suspect not original prop and probably not the size the boat started with either.
Possibly the prop was cheap,available and it fitted !
If you can live with it, leave well alone and at some future point if prop needs attention get it cut down and re pitched to compensate.
Would look out on ebay for suitable 4 blade, which it may have had to start with.
3 blade might have been fitted in misguided attempt to go faster .

I think you might right about the prop not being original. Boat goes around 3-4 knots when idling in gear. Is a 4 blade prop better than 3? (I'm still new at boating )

 

[oldgit]

I think you might right about the prop not being original. Boat goes around 3-4 knots when idling in gear. Is a 4 blade prop better than 3? (I'm still new at boating )

Having had both types very recently, would say that the 4 blade felt to have more bite and appeared to cause less vibration.
Most immediately noticeable thing on the four blade prop, you opened the throttle and the boat just went, the three blade prop seems to thrash around for bit before getting a grip.
Mind you two totally different engines, first boat had luverly lazy 6 litre Perkins developing 135 HP, the following boat has a lawnmower capacity of 3.6Litre developing 200HP.
Wonder which one will last longest
Four blade props tend to be considerably more expensive to buy new.

 

[Portofino]

There are two types of vibration in propellers ,and may be classified according to their frequency.
Once per revolution caused by
1- uneven pitch among the blades
2- blades unequally spaced
3- blades of none uniform weight
4- blades of non - uniform smoothness.
5-dissimilarity of blade patterns
6- unequal damage or smoothness.
Vibrations occurring at blade frequency say three tines per revolution may arise out of either the following:
1- Restriction on the inflow of water at the top
2- Hull suction.

Once per revolution the cure I’d remove and replace with accurate props machined for correct pitch and balance .

With blade frequency type of vibration and noise it’s usually the lack of clearance at the top leading to poor inflow .
Generally on clean running planing boats the props should be clear of the hull by at least 20 % of the diameter for singles , dropping to around 18 % for multiple prop set ups .

Also additionally it’s essential to minimise obstructions forward of the prop as well as those aft like rudders .
A rudder aft may vibrate at blade frequency unless it’s faired into the slipstream, can,t really see from the pic .But the forces hear are less than any forward obstruction and the rudder effect will be less pronounced.
Looking at the pic there’s potential for fwd obstruction .

Work on propeller vibration and noise is well documented.

 

[Divemaster1]

Jupiter 33 ... great Danish produced boat ... believe it is derived from a split at Baess Boats (They made the Apollo 32), so of equal high quality craftmanship... A lot of similarities between the boats..... (We had an Apollo 32 with twin Ford 120's).

This noise is perfectly normal... you are within inches from the prop in the aft cabin, so inevitably there will be some noise from that fast spinning thingie that throws water into swirls as it propels the boat forward ... inevitably some of that will be thrown upwards towards the aft cabin sole...

The space between propeller and hull looks ample in the last picture ... , so should not be anything to worry about ...

If there is little/no vibration in eh shaft (observe in engine room when running), then I would not worry at all about the noise.. We usually closed the hatches and doors tot he aft cabin when underway to reduce the noise at the helm, so if it bothers you then simply do that and enjoy the great and well-made vessel she is !

 

[QBhoy]

Only read the first few replies...but it’s certain that the prop diameter is far too large. It seems to have a very shallow pitch and an over sized diameter. Someone has made a mess of propping the boat. Pretty sure this will be to blame, presuming all else is well in terms of cutlass bearing and shaft alignment.

Perhaps a good idea to get some data to re prop.
Info required;
Max rpm rating for engine
Gear reduction ratio
Gps speed at wot
Current pitch of prop.

 

[QBhoy]

Ok. So just looked at other pics. If that’s the same prop as the other pics...it doesn’t look that close to the hull.
I’d be looking at the shaft alignment if it’s that bad.
If it’s ok...might just need the prop balanced over winter.

 

[royaldo]

Jupiter 33 ... great Danish produced boat ... believe it is derived from a split at Baess Boats (They made the Apollo 32), so of equal high quality craftmanship... A lot of similarities between the boats..... (We had an Apollo 32 with twin Ford 120's).

This noise is perfectly normal... you are within inches from the prop in the aft cabin, so inevitably there will be some noise from that fast spinning thingie that throws water into swirls as it propels the boat forward ... inevitably some of that will be thrown upwards towards the aft cabin sole...

The space between propeller and hull looks ample in the last picture ... , so should not be anything to worry about ...

If there is little/no vibration in eh shaft (observe in engine room when running), then I would not worry at all about the noise.. We usually closed the hatches and doors tot he aft cabin when underway to reduce the noise at the helm, so if it bothers you then simply do that and enjoy the great and well-made vessel she is !

Sorry I missed the last repiles.

Yes, as I know the story, Baess was working together with the 'Bogø shipyard' who made the Jupiter boats from the 60's until bankruptcy in the middle of the 70's. When the collaboration between Baess and Bogø ended, he got an empty Jupiter 31 hull with him and from this the Apollo 32 was created, so yes the Apollo boats has a lot in common with the old danish Jupiter boats. The 33 is 10.5 meters long and 3.6 meters wide, so slightly bigger than the Apollo 32 but still very similar in construction.

Thanks, nice to know that some noise is to be expected. The noise doesnt bother me that much, just want to be sure that the mechanical stuff is in correct working condition.

How about slight vibrations when turning in oncoming current? Rudder has very little play. We had the rudder checked/disassembled and lubed last winter.

There does not seem to be vibrations on the propellershaft (see video)

https://www.youtube.com/watch?v=p5LQ_f-cSqs

 

[John and charmaine beatti]

Having had both types very recently, would say that the 4 blade felt to have more bite and appeared to cause less vibration.
Most immediately noticeable thing on the four blade prop, you opened the throttle and the boat just went, the three blade prop seems to thrash around for bit before getting a grip.
Mind you two totally different engines, first boat had luverly lazy 6 litre Perkins developing 135 HP, the following boat has a lawnmower capacity of 3.6Litre developing 200HP.
Wonder which one will last longest
Four blade props tend to be considerably more expensive to buy new.

Hi there ,
We have a Jupiter 33 with 6 cylinder perkins in fresh water in northern Ireland can you tell me the correct size propeller for this boat as I'd like to get a spare due to water being very low this year we got some damage to propeller and all I know is its a LH