Slight vibration - what could it be?

[The Hunky Dory]

The boat's 6 years old, and for the first 5 years ran as smooth as silk. However, we now get a slight vibration when moving, and the engine visibly shakes a bit at various rev ranges(but not at all when out of gear). So, the problem as I see it can only be in one or more of these components:

- Prop out of balance

- prop shaft bent

- cutlass bearing worn (we've got a Volvo water lubricated seal)

- Centaflex flexible coupling faulty

- engine out of line

- engine mounts failing

Are there any components I've missed?

We're coming out of the water in March for blacking. I want to solve this problem at the same time, so we're replacing the cutlass bearing, having the prop rebalanced, and replacing the Volvo seal (which has just started dripping occasionally) at the same time. Any other suggestions.

[ditchcrawler]

The boat's 6 years old, and for the first 5 years ran as smooth as silk. However, we now get a slight vibration when moving, and the engine visibly shakes a bit at various rev ranges(but not at all when out of gear). So, the problem as I see it can only be in one or more of these components:

- Prop out of balance

- prop shaft bent

- cutlass bearing worn (we've got a Volvo water lubricated seal)

- Centaflex flexible coupling faulty

- engine out of line

- engine mounts failing

Are there any components I've missed?

We're coming out of the water in March for blacking. I want to solve this problem at the same time, so we're replacing the cutlass bearing, having the prop rebalanced, and replacing the Volvo seal (which has just started dripping occasionally) at the same time. Any other suggestions.

Engine drive plate breaking up

[Tony Brooks]

The boat's 6 years old, and for the first 5 years ran as smooth as silk. However, we now get a slight vibration when moving, and the engine visibly shakes a bit at various rev ranges(but not at all when out of gear). So, the problem as I see it can only be in one or more of these components:

- Prop out of balance

- prop shaft bent

- cutlass bearing worn (we've got a Volvo water lubricated seal)

- Centaflex flexible coupling faulty

- engine out of line

- engine mounts failing

Are there any components I've missed?

We're coming out of the water in March for blacking. I want to solve this problem at the same time, so we're replacing the cutlass bearing, having the prop rebalanced, and replacing the Volvo seal (which has just started dripping occasionally) at the same time. Any other suggestions.

 

 

Depending upon which Centaflex coupling - serviceable engine mounts that have dropped a bit over time so the shaft is now out of alignment (which you cover with engine out of line).

 

Nuts and bolts on one or more mounts loose, either the ones that hold the mount to the bed or the engine foot onto the mount.

[steelaway]

The boat's 6 years old, and for the first 5 years ran as smooth as silk. However, we now get a slight vibration when moving, and the engine visibly shakes a bit at various rev ranges(but not at all when out of gear). So, the problem as I see it can only be in one or more of these components:

- Prop out of balance

- prop shaft bent

- cutlass bearing worn (we've got a Volvo water lubricated seal)

- Centaflex flexible coupling faulty

- engine out of line

- engine mounts failing

Are there any components I've missed?

We're coming out of the water in March for blacking. I want to solve this problem at the same time, so we're replacing the cutlass bearing, having the prop rebalanced, and replacing the Volvo seal (which has just started dripping occasionally) at the same time. Any other suggestions.

 

 

Hi

 

I imagine you have checked there is nothing on the prop.

While you are there you might be able to see/feel for any play.

Also check the weed hatch is correctly seated, this can rattle like crazy if its not.

You should also be able to see a faulty engine mount, the centre screw can also be touching the bed if its a long way through and the mountings have settled.

 

Alex

[AlanM6]

I,m getting a tinny rattling sound thats driving me nuts, it only happens when the boat is in gear and moving along at certain speeds, at

what I estimate to be my average cruising speed 2.75--3 mph its fine(sweet as a nut) throttle up a little and the rattling begins slow down a little its there!

Ive removed all loose objects and tools from under the engine bay, checked the the eberspacher was secure in its housing, still there.

I thought I had it cracked today when I found the air filter cover to be a little on the loose side so I removed it changed the filter while I was at it and BINGO no Rattle!! well not for 10 mins or so, now its back again and still driving me crazy.

Edited October 24, 2010 by AlanM6

[steelaway]

I,m getting a tinny rattling sound thats driving me nuts, it only happens when the boat is in gear and moving along at certain speeds, at

what I estimate to be my average cruising speed 2.75--3 mph its fine(sweet as a nut) throttle up a little and the rattling begins slow down a little its there!

Ive removed all loose objects and tools from under the engine bay, checked the the eberspacher was secure in its housing, still there.

I thought I had it cracked today when I found the air filter cover to be a little on the loose side so I removed it changed the filter while I was at it and BINGO no Rattle!! well not for 10 mins or so, now its back again and still driving me crazy.

 

 

Hi

 

See above - I have also heard a 'singing prop' can be like this.

 

Alex

[AlanM6]

Thanks Alex.

The boat was out of the water last week for blacking I checked the prop and rudder for any play, they both looked fine to me, but I,m no expert

[Chalky]

Have you checked the coupling between the gearbox and the prop shaft? I had this come loose and it caused a some interesting vibration (fortunately I caught it before any serious damage was done). Also try changing the gearbox oil - that can sometimes lead to strange noises if its past its best and it's a relatively cheap thing to do.

[jelunga]

I,m getting a tinny rattling sound thats driving me nuts, it only happens when the boat is in gear and moving along at certain speeds, at

what I estimate to be my average cruising speed 2.75--3 mph its fine(sweet as a nut) throttle up a little and the rattling begins slow down a little its there!

Ive removed all loose objects and tools from under the engine bay, checked the the eberspacher was secure in its housing, still there.

I thought I had it cracked today when I found the air filter cover to be a little on the loose side so I removed it changed the filter while I was at it and BINGO no Rattle!! well not for 10 mins or so, now its back again and still driving me crazy.

This can occur at certain speeds /depths and I think it depends on prop design / condition. Cavitation maybe in shallow water.

[AlanM6]

I will change the gearbox oil next week. I did notice that it was a showing a little on the high side on the dip stick,I,ll double check the couplings and see if that helps. Cavitation now thats an interesting one, wasn,t sure what it meant, so I googled it and found some interesting videos, that gave me an idea I haven,t really tried it in reverse so I will give that a go today.So if any one sees me crusing backwards today at 4mph give me plenty of room.

Thank you all for your suggestions this forum is a big help for a novice like me.

Alan.

[The Hunky Dory]

Thanks for the comments on my original problem.

 

Ditchcrawler, how would I know if its the drive plate - any way of checking this. On a Beta 43 thats 6 years old, 3000 clock hours, would this failure be expected around now?

 

The mount bolts are tight, but to get the correct shaft/engine alignment they're adjusted quite high up the thread. This makes me feel that there's more possibility of movement under load. Could this cause more vibration.

 

Weed hatch is OK. Feeling the prop, it has quite a few battlescars on the leading edge of each blade, but its hard to tell whats "normal" wear.

[RobinJ]

The boat's 6 years old, and for the first 5 years ran as smooth as silk. However, we now get a slight vibration when moving, and the engine visibly shakes a bit at various rev ranges(but not at all when out of gear). So, the problem as I see it can only be in one or more of these components:

- Prop out of balance

- prop shaft bent

- cutlass bearing worn (we've got a Volvo water lubricated seal)

- Centaflex flexible coupling faulty

- engine out of line

- engine mounts failing

Are there any components I've missed?

...

Can be difficult to locate!

What difference does it make in gear/out of gear?

If you disconnect the centraflex (normally 4 bolts) it could help to identify if its a power unit problem/propshaft problem, also whether its still aligned?

It could be badly matched valve clearances or timing chain wear or some of the things already mentioned.