Inboard diesel

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From: mmts1 (Original Message) Sent: 11/11/2007 12:22 AM
I have a small volvo penta single cylinder driving a 2 blade prop the performance is ordinary and the vibration resonating thru the hull high. the engine is mounted in a steel frame with resilient mounts. the engine idles fine and revs in neutral o.k. Does anyone have similar vibration issues, is this vibration due to cavitation would a three blade prop make any difference. the prop shaft exits the hull on the centreline, with lots of wide rudder in the way. My top hat is a Mk1

Any help appreciated



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Recommend Message 2 of 9 in Discussion

From: nswsailor Sent: 11/11/2007 1:07 AM
Hi, No Name!

My Mk1 has the same problem and I know exactly what the cause is!

The alignment of your engine and your prop shaft is out!

To fix the problem you have to re aline the engine with the prop shaft by adjusting
your engine mounts. You will need special gear for it, so I will be getting a marine engineer to do the job and the question really is-- dose anybody know of a person
who is compentant in doing the realinement? I'm on the NSW Mid North Coast.

Phillip
SEAKA.
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Recommend Message 3 of 9 in Discussion

From: Rob Sent: 11/11/2007 1:11 AM
It sounds like the prop shaft may be out of alignment, or even bent. If the engine is idling Ok and the vibrations are only occurring when the shaft is rotating it's either the shaft or the prop itself may have been damaged. If, when you rotate the shaft by hand, there is any lateral movement, it's the shaft.

I hope this might help!

Rob
Isabella II (Mk II) Pittwater

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Recommend Message 4 of 9 in Discussion

From: mmts1 Sent: 11/11/2007 1:30 AM
Thanks Phillip, and Rob
Seems like alignment is the place to start. Initial observations by Mk 1 eyeball doesn't really show misalignment but then again I suppose it doesn't take much to throw everything out. Will get the experts to check it out. What is your top speed under motor, I reckon I'd be lucky to be doing 3-4knots, throw in a strong head wind I'd probably go backwards. Do these boats generally have 2 blade props. I've just purchased my boat today, lots of tidying up and little jobs to do, Might see you on the water I'm up Brooklyn way

Regards

Mark

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Recommend Message 5 of 9 in Discussion

From: Rob Sent: 11/11/2007 1:37 AM
Hi again Mark
My Mk II will do around 4.5 knots under motor (9 hp Drofin diesel), less with a headwind, more under full throttle (not worth it). Any amount of growth will dramatically slow me down - the prop's effectiveness diminishes very quickly if not clean and smooth. It is a 2 blade prop - quite small but seems well matched to the motor. At least with the inboard, the prop is well underwater all the time, even in a seaway, so it's always pushing water, not air!
Good luck with the vibration,
Rob

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From: nswsailor Sent: 12/11/2007 1:39 AM
Hi Mark,

At full throttle I can do 6 knots with a clean bottom, but then I have a 9hp Nanni with a three blade prop. Needless to say I only take SEAKA to 4 knots at present until I can get a realignment. Any growth will reduce speed by 2 knots at least.

What is your boat name?

Phillip
SEAKA

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Recommend Message 7 of 9 in Discussion

From: mmts1 Sent: 12/11/2007 2:48 AM
Thanks Phil,

Paid for the boat today, the boats name is "Mari Anne" don't know any Mari Annes but will get used to it

Thanks

Mark




----Hi Mark,

At full throttle I can do 6 knots with a clean bottom, but then I have a 9hp Nanni with a three blade prop. Needless to say I only take SEAKA to 4 knots at present until I can get a realignment. Any growth will reduce speed by 2 knots at least.

What is your boat name?

Phillip
SEAKA

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Recommend Message 8 of 9 in Discussion

From: SilverGull Sent: 13/11/2007 3:10 AM
I have just fixed this problem last week ! The shaft was seriously out of alignment resulting in damage to the shaft. Resulted in leaks through gland. Result new Gland and Packing, New Shaft, New Prop ! New Skeg Bearings and 920 of labour. So the end result inclusing Antifouling came to $5.4K, I did also get the engine serviced and new stripe on the boat + antifouling etc. Still the majority of the cost was the shaft...prop along cost $450 and the Shaft $250. Not sure if I was completely ripped off, never know with these things, but its all back in order now. EMail me if you need more info Denis

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Recommend Message 9 of 9 in Discussion

From: mmts1 Sent: 14/11/2007 12:29 AM
Thanks for the info Denis, lets hope i'm not looking at a 5.4k repair. Will start with a engine shaft alignment as per the text book (which I'll have a go at myself) Failing that will call in experts. I guess your boat purrs like a kitten and glides thru the water now, btw what sort of prop did you get, what size diesel do you have and where did you have all the work done

Regards
Mark