New engine vibrating and prop clearance

[Nat]

Hello, Im new to boating and new to this forum so, hello, and sorry for any cross posting.

 

I have just bought a 5 year old cruiser shell (insulated with windows) which I plan to fit out myself (with help along the way), but have had the engine and all the stern gear put in profesionaly.

 

There seems to be a couple of things not quite right with this and would greatly appreciate some advise. ..

 

Firstly ...the engine (vetus 42) sounds great in idle! But when i put it into gear an almighty rattling starts, to the extent that my neighbour across the yard can feel it vibrating his boat. I have checked the engine mounts and they appear solid.

 

The other thing, that i think could be the cause of this, is the clearance between the tip of the prop and the skeg below. I have measured it and there is only a 4mm gap!!! I imagine this wont make too much of a difference to the actual propolsion of the boat but seems like it could be a nightmare for things getting trapped down there. It looks like they only measured from the inside when they cut the stern hole and didnt check from the outside?

The boat was the first boat Darke Steel ever made so, although the build quality seems very sturdy I think the measurements might have been a little unusual, particularly for the stern and im not sure the fitters checked this thoroughly.

 

 

I will be speaking to the fitters soon but want to be a bit more clued up before i do. The scenario of taking everything out, patching it up and putting it in a few inches higher, is running through my head and it doesnt sound too appealing.

 

Any thoughts on how I should appraoch this would be very appreciated.

 

 

[bigste]

That gap is tight, very tight. However, that should not be causing the noise and vibration. Have you tried running it without the prop. Apart from that with a gap like that your weed hatch wiil get plenty of use.

[Dalslandia]

Min clearance for a 3 blade is; 17% on top, and 4% below,

% of propeller diameter that is.

or minimum 2 inch

[ROBDEN]

High Nat and welcome to the forum.

 

What gearbox is attached to the Vetus?

Vetus had trouble with the driveplate matching the gearbox a while ago and ended up altering them.

Runs well out of gear but as soon as forward or reverse selected it sounded like a bag of nails.

 

Rob....

[Tony Dunkley]

Hello, Im new to boating and new to this forum so, hello, and sorry for any cross posting.

 

I have just bought a 5 year old cruiser shell (insulated with windows) which I plan to fit out myself (with help along the way), but have had the engine and all the stern gear put in profesionaly.

 

There seems to be a couple of things not quite right with this and would greatly appreciate some advise. ..

 

Firstly ...the engine (vetus 42) sounds great in idle! But when i put it into gear an almighty rattling starts, to the extent that my neighbour across the yard can feel it vibrating his boat. I have checked the engine mounts and they appear solid.

 

The other thing, that i think could be the cause of this, is the clearance between the tip of the prop and the skeg below. I have measured it and there is only a 4mm gap!!! I imagine this wont make too much of a difference to the actual propolsion of the boat but seems like it could be a nightmare for things getting trapped down there. It looks like they only measured from the inside when they cut the stern hole and didnt check from the outside?

The boat was the first boat Darke Steel ever made so, although the build quality seems very sturdy I think the measurements might have been a little unusual, particularly for the stern and im not sure the fitters checked this thoroughly.

 

 

I will be speaking to the fitters soon but want to be a bit more clued up before i do. The scenario of taking everything out, patching it up and putting it in a few inches higher, is running through my head and it doesnt sound too appealing.

 

Any thoughts on how I should appraoch this would be very appreciated.

 

 

The sort of noise and vibration you're describing won't be caused by the small clearance between the blade tips and the skeg. There is something in the drive train ( engine flywheel to propellor) that's loose, bent or out of alignment.

Is the boat in the water or still out on hardstanding as in the photos ?

[system 4-50]

I'm no engineer but the bit of box section between the hull & the skeg proper looks like a complete bodge to me, assuming I'm seeing the picture right. Its going to catch on stuff surely?

[Tony Dunkley]

I'm no engineer but the bit of box section between the hull & the skeg proper looks like a complete bodge to me, assuming I'm seeing the picture right. Its going to catch on stuff surely?

That will depend on how the forard end of it is finished and tapered off up to the bottom plating, but you're right, it's a bloody awful job. The primary concern I'd have about it would be it's strength and durability (very thin walled box section between the bottom plating and the skeg), and it's effect on the inflow of water to the propeller, assuming that the forard end of it is covered with a fairing plate.

[X Alan W]

Looking at the photo's it appears that the stern gear has been fitted to low in the swim & an extra piece of box section has had to be fitted to allow the prop to clear the skeg with a lot of clearance between prop & uxter plate, possibly caused by the engine bed installation not being high enough. I'm wondering if the stern gear was fitted to suit the engine unit sitting on the beds rather than fitting the stern gear approx halfway up the swim & mounting the engine to suit

[alan_fincher]

I'm no engineer but the bit of box section between the hull & the skeg proper looks like a complete bodge to me, assuming I'm seeing the picture right. Its going to catch on stuff surely?

 

Sadly I agree.

 

Even though the skeg has been lowered in that way the stern tube still seems far too low down the stern post.

 

There is masses of space above te prop, but that minimal gap at the bottom will be a total nightmare.

 

Anything less than about 2" is far from ideal.

 

I think it needs re-engineering to raise that prop shaft, but this will then presumably affect propshaft alignment to engine, unless engine beds are also raised.

 

None of this may have anything to do with the vibration, but what on earth were they thinking of ?

[Albion]

Another source of rattle can be the edge of the weed hatch bottom plate rattling against the aperture in the uxter plate. This will only apply if it is the type of hatch lower plate that sits loose in the aperture, supported from above, as opposed to being clamped down on top of the uxter. It is unlikely to give the massive rattle that you claim but it would be worth looking for any bright spot on the edge of the plate where it sits in the aperture.

I also agree with other comments about it being a poor build with the shaft in the incorrect height down the stern post.

Roger

[Tony Dunkley]

 

There is masses of space above te prop, but that minimal gap at the bottom will be a total nightmare.

 

Anything less than about 2" is far from ideal.

 

 

That isn't so. This particular point about small clearances between the blade tips and the skeg has been brought up on here before. It seems to be a sort of instinctive reaction to look at a small gap like that and think that because it's small that more stuff is going to get caught in it, but if you think about it more and ask yourself about what can get trapped in a small gap in comparison with what can get trapped in a bigger (2'') gap, then the initial thoughts start to make a lot less sense.

In this particular instance with that very thin blade section Vetus propeller, the effect of the skeg construction on the water inflow may induce propeller 'singing' at certain speeds, but the minimal gap at the blade tips isn't a problem.

[howardang]

Hello, Im new to boating and new to this forum so, hello, and sorry for any cross posting.

 

I have just bought a 5 year old cruiser shell (insulated with windows) which I plan to fit out myself (with help along the way), but have had the engine and all the stern gear put in profesionaly.

 

There seems to be a couple of things not quite right with this and would greatly appreciate some advise. ..

 

Firstly ...the engine (vetus 42) sounds great in idle! But when i put it into gear an almighty rattling starts, to the extent that my neighbour across the yard can feel it vibrating his boat. I have checked the engine mounts and they appear solid.

 

The other thing, that i think could be the cause of this, is the clearance between the tip of the prop and the skeg below. I have measured it and there is only a 4mm gap!!! I imagine this wont make too much of a difference to the actual propolsion of the boat but seems like it could be a nightmare for things getting trapped down there. It looks like they only measured from the inside when they cut the stern hole and didnt check from the outside?

The boat was the first boat Darke Steel ever made so, although the build quality seems very sturdy I think the measurements might have been a little unusual, particularly for the stern and im not sure the fitters checked this thoroughly.

 

 

I will be speaking to the fitters soon but want to be a bit more clued up before i do. The scenario of taking everything out, patching it up and putting it in a few inches higher, is running through my head and it doesnt sound too appealing.

 

Any thoughts on how I should appraoch this would be very appreciated.

 

 

It is slightly difficult to judge from the photos but are you happy that you can reach the propeller through the weed hatch? It looks a big gap to me.

 

Howard

[MtB]

 

Sadly I agree.

 

Even though the skeg has been lowered in that way the stern tube still seems far too low down the stern post.

 

There is masses of space above te prop, but that minimal gap at the bottom will be a total nightmare.

 

Anything less than about 2" is far from ideal.

 

I think it needs re-engineering to raise that prop shaft, but this will then presumably affect propshaft alignment to engine, unless engine beds are also raised.

 

None of this may have anything to do with the vibration, but what on earth were they thinking of ?

 

 

Looks to me as though the stern tube was positioned to suit the blade, rather than the other way around.

 

Dear OP, did you supply the blade and say 'fit this'? It looks far too big in diameter for the height of the swim (from baseplate to uxterplate), and lead to that rather flimsily lowered skeg.

 

 

MtB

[Nat]

Wow, thanks for all the response.

 

The sort of noise and vibration you're describing won't be caused by the small clearance between the blade tips and the skeg. There is something in the drive train ( engine flywheel to propellor) that's loose, bent or out of alignment.

Is the boat in the water or still out on hardstanding as in the photos ?

 

Hi Tony, its still on hard standing and the engineers are onsite so should be able to get them to look at it.

 

 

 

I also agree with other comments about it being a poor build with the shaft in the incorrect height down the stern post.

 

 

 

The shaft was put in by the fitters of the engine not the boat builders.

 

It is slightly difficult to judge from the photos but are you happy that you can reach the propeller through the weed hatch? It looks a big gap to me.

 

Howard

 

Yes that shouldnt be too much of a problem

 

 

 

Looks to me as though the stern tube was positioned to suit the blade, rather than the other way around.

 

Dear OP, did you supply the blade and say 'fit this'? It looks far too big in diameter for the height of the swim (from baseplate to uxterplate), and lead to that rather flimsily lowered skeg.

 

 

MtB

 

Mtb, I decided not to supply anything myself to avoid this happening. The boxing was already in place before the the gear was fitted. I think the blade would be fine though if the stern tube had been positioned properly. To confirm, ALL the stern gear was put in with the engine, encluding the drilling of it etc.

 

 

 

 

 

I think it needs re-engineering to raise that prop shaft, but this will then presumably affect propshaft alignment to engine, unless engine beds are also raised.

 

None of this may have anything to do with the vibration, but what on earth were they thinking of ?

 

I know, it seems a completely ridiculous oversight to me! Yes, everything would need to be raised. But Im not too sure the fitters will be too happy about that!?!

[Boat&Bikes]

Have you brought the shell from Darke steel and then had the engine/prop fitted by others?

 

Ian.

[Tony Dunkley]

 

Hi Tony, its still on hard standing and the engineers are onsite so should be able to get them to look at it.

 

 

As you're still out of the water there are some simple preliminary checks you can do yourself. Turn the propellor by hand through at least one full revolution to feel if there's any binding or increased effort needed to turn it at any point in one complete turn, and then measure the clearance to the skeg on all three blade tips to see if they're all the same.

The noise and vibration could be coming from a misaligned coupling or a bent shaft and those are the easiest potential faults to check first and eliminate.

Is the engine and gearbox a new factory assembled unit, or a secondhand engine with another make of gearbox fitted ?

Edited March 31, 2015 by Tony Dunkley

[Guest]

Looking at the photo's it appears that the stern gear has been fitted to low in the swim & an extra piece of box section has had to be fitted to allow the prop to clear the skeg with a lot of clearance between prop & uxter plate, possibly caused by the engine bed installation not being high enough. I'm wondering if the stern gear was fitted to suit the engine unit sitting on the beds rather than fitting the stern gear approx halfway up the swim & mounting the engine to suit

My very thoughts. Same engine/setup in my boat and the tube is much more central between skeg and weed hatch. I'll guess the engine mounts are too low, perhaps with a different engine in mind originally.

[gazza]

The only reason for fitting the engine low in the hole would be for head/manifold clearance. I doubt that would be an issue.

 

Ideally the sterngear would have been drilled on the centreline - this would have allowed correct prop clearance and selection as well as avoiding that ghastly mess of a skeg - 100 x 50 channel would have been a better choice for that than the box they have used, regardless of location of the shaft

 

Would it be mine I would insists they start again. Its not a pretty installation at all.

[dor]

If you are trying to run the enghine when the boat is out of the water, the shaft bearing can create a shuddering noise if it is a Vetus water-lubricated one. The shaft runs in a rubber sleeve and if water isn't present, the bearing runs dry and the rubber 'catches' on the shaft and can set up a pretty fearful vibration. It will also damage the bearing.

 

Also, you need to check the engine mounts very carefully. They may all appear to be tight and sound, but if the diagonals are not set up right, then the engine will shake when under load. I'm assuming you have checked the obvious one - shaft alignment.

[Tony Dunkley]

If you are trying to run the enghine when the boat is out of the water, the shaft bearing can create a shuddering noise if it is a Vetus water-lubricated one. The shaft runs in a rubber sleeve and if water isn't present, the bearing runs dry and the rubber 'catches' on the shaft and can set up a pretty fearful vibration. It will also damage the bearing.

 

Also, you need to check the engine mounts very carefully. They may all appear to be tight and sound, but if the diagonals are not set up right, then the engine will shake when under load. I'm assuming you have checked the obvious one - shaft alignment.

 

He hasn't put it under load yet, other than frictional losses in the gearbox and tailshaft bearings and what bit of air the propeller moves about.

Edited March 31, 2015 by Tony Dunkley

[Nat]

Have you brought the shell from Darke steel and then had the engine/prop fitted by others?

 

Ian.

I didnt buy it from darke steel, I only recently bought it as second hand without the engine etc

 

 

As you're still out of the water there are some simple preliminary checks you can do yourself. Turn the propellor by hand through at least one full revolution to feel if there's any binding or increased effort needed to turn it at any point in one complete turn, and then measure the clearance to the skeg on all three blade tips to see if they're all the same.

The noise and vibration could be coming from a misaligned coupling or a bent shaft and those are the easiest potential faults to check first and eliminate.

Is the engine and gearbox a new factory assembled unit, or a secondhand engine with another make of gearbox fitted ?

Great thanks for the check list.

I turned the blade already and noticed that it is consistantly quite stiff in comparison to the others I tried.

The engine and gearbox (prm) are new and factory fitted

[MtB]

I don't think you've addressed Dor's question about whether this is a Vetus branded stern tube. If it is a Vetus, then it relies on canal water to lubricate it.

 

if run it dry, the rubber bearing will probably knacker itself immediately. This would account for the horrendous noise you describe, and also the resistance to turning by hand you mention. If you push to gently to turn the blade against the resistance, does it feel 'springy'? Does the blade move back slightly when you stop pushing and let go?

 

MtB

[Tony Dunkley]

 

Great thanks for the check list.

I turned the blade already and noticed that it is consistantly quite stiff in comparison to the others I tried.

The engine and gearbox (prm) are new and factory fitted

 

 

If the shaft is consistently stiff and hard to turn by hand throughout the whole of one complete revolution, then, taking into consideration the severity of the vibration( if it could be felt through the ground on a neighbouring boat) it indicates probable severe misalignment at the gearbox to tailshaft coupling. This may be due to the engine and box being misaligned (gearbox output flange centre axis not aligned with the centre axis of the tailshaft) or, depending on the make and type of the coupling, that itself could be incorrectly fitted to the tailshaft or incorrectly assembled. Do you know the make and type of the coupling, or failing that can you describe it. A picture would be good.

Also , to address the points made by dor and MtB, is the sterntube a water or grease lubricated type ? It doesn't look like any of the Vetus water lubricated jobs that I've seen, they've all had bronze outer bearing housings with small water intake scoops on either side, but there are water lubricated stern tube assemblies available with a feed at the stuffing box end, bled off from the raw water circuit of a heat exchanger cooling system. Is your installation keel cooled (with an internal skintank) or is it heat exchanger cooled with a raw water intake from the canal and an overboard discharge, either via a wet exhaust system or a separate skin fitting.

Edited March 31, 2015 by Tony Dunkley

[dor]

 

He hasn't put it under load yet, other than frictional losses in the gearbox and tailshaft bearings and what bit of air the propeller moves about.

By under load I was referring to the engine. Engaging a gearbox and tight prop shaft is putting the engine under load. Even with a freely rotating Vetus shaft bearing, the vibration set up can be quite startling.

[Tony Dunkley]

By under load I was referring to the engine. Engaging a gearbox and tight prop shaft is putting the engine under load. Even with a freely rotating Vetus shaft bearing, the vibration set up can be quite startling.

 

He's said that it's possible to turn the prop by hand, so any load on the engine with the boat out of the water is going to be minimal, but severe misalignment at the gearbox / tailshaft coupling can certainly cause some almighty vibration. I would be very surprised if a dry or damaged bearing would cause anything bad enough to be transmitted through the ground to be felt on a nearby boat.

Edited March 31, 2015 by Tony Dunkley