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Unfortunately we have picked up some 14mm three strand nylon rope arround the propshaft.
The rope wound itself (while the prop was turning) arround the blades and then wound itself up the shaft (like a screw thread) up to the cutlas bearing. There is no apparent damage to prop, shaft or external cutlass bearing housing.
I have now managed to cut all of the rope off.
The action of the rope winding up the shaft appears to have pulled the shaft out about 2 inches i.e. an extra 2 inches of shaft is visable on the out side. On the inside I can se no problem, no water is comming through the bearing, the bolts on the shaft joint are secure and the shaft rotates by hand ok with no side to side slack.
I have not yet risked starting the engine.
Does anyone have any view as to possible damage ?, is this an engine / gearbox out job ?.
I am having Soyakaze taken to the Keyhaven scrubing bearth (using the boat yard tug) as I cant examine it properly out in the river mud. Any advice on what I should look for ?
Thanks
Phil
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Eric Richardson
Apr 27, 2013 - 10:54AM
Re: Propshaft - Advice / help please
Hi Phil
If you now have 2" more prop shaft protruding then as you say something has moved. That would put your prop pretty close to the rudder, are you sure its not just polished the shaft?
Ok it's moved what next.
Check that the engine has not moved on it's mountings!!
Check where the shaft fits into the various couplings to see if it has drawn the shaft in the couplings!!
Very unlikely but check that the gearbox coupling has not moved back from the back of the gearbox, I have never met this. Engine mountings are a fair possibility if the shaft has actually moved backwards.
Hope that helps
Eric
SeaDog Name (if owner or crew) Ex
Phil
May 9, 2013 - 12:07AM
Re: Propshaft - Advice - update Engines out
Hello Eric
We now have the engine out, unfortunately its bad news.
The bolts that attach the brackets to the engine block have been snapped !, the brackets bent and the gearbox drive plate is us. There are also some other problems, i.e. leaking crankshaft seal and water pump leaks.
I have been offered a good deal on a recon Volvo 2040 and matching gearbox so we are going for that aas a more reliable (and up todate) option. The MD 2040 is smaller and will give more room for maintenance.
Have you any views on the MD2040 ? and do you think the same prop will work ?
Regards - Phil
SeaDog Name (if owner or crew) Soyakaze
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John Lansdell
May 10, 2013 - 5:09PM
Re: Propshaft - Advice - update Engines out
When we replaced the Perkins with a Beta (Kubota) I found it was a higher revving engine, and thus was overpropped with the original propellor. Depending on the gearbox you may find it does not rotate in the same direction as it would have done with the B-W Velvet Drive unit.
SeaDog Name (if owner or crew) Twotails
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Graham
May 10, 2013 - 5:30PM
Re: Propshaft - Advice - update Engines out
I agree re the prop direction, check at least twice! When we changed engine on Dougal I was having the folding prop re-furbed and re-pitched to suit. BetaMarine specified the changes required. Unfortunately they forgot that I was retaining the BW gearbox so the direction should have remained the same. The error was not realised until we launched and found that forward gear made us move backwards. Fortunately BetaMarine admitted their mistake and paid the additional costs of lift-out and re-launch.
SeaDog Name (if owner or crew) Dougal
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Phil
May 22, 2013 - 12:08AM
Re: Propshaft - Advice - update Engines out
Hi Graham & John
Unfortunately you are correct the rotation of the MD2040 is RH while the Perkins is LH.
The engine power curve is different and therfore the prop size / pitch is also different, the calcs indicate that a 17 x 11 would give best performance on the MD2040.
So, we now have the engine out, propshaft, seal, and cutlass bearing out and the stern gland, exhaust and primary electrics out.
We removed the stern gland as a precaution as the old cutlass bearing was badly damaged and "dezincified". It took 2 days and much cursing to remove the cutlas and stern gland.
With luck we will be on sea trials in about 2 weeks time with the new MD2040.
One question to others who have "re-engined" - did you keep the old exhaust routing ?i.e. under the port side rear bunk and out through the transome.
Regards - Phil
SeaDog Name (if owner or crew) Soyakaze
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John Lansdell
May 22, 2013 - 5:17PM
Re: Propshaft - Advice - update Engines out
I do not like dry exhausts. Twotails now has a "wet" exhaust. Water is injected into the exhaust stub just below the exhaust outlet to ensure none gets back into the engine. A vertical(ish) pipe then goes down to a Vetus box alongside and outboard of the engine alongside and below the fuel tank. A Vetus anti-syphon bend is fitted where the Parsons Box was and the output from this is taken vertically down to a bend connecting with a new pipe going aft to the original stern outlet. It seems to work OK. Hope this helps. John L.
SeaDog Name (if owner or crew) Twotails
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Eric Richardson
May 22, 2013 - 7:30PM
Re: Propshaft - Advice - update Engines out
Hi Phil
Sorry I did not get back to you earlier, not sure who makes that engine! Volvo buy in most marine engines from other makers and badge them. If my memory is correct it is a Japanese 3 cylinder job.
That is not to say anything against it except to advise that you try to ascertain its makers then the spares will go down in price by about 60%.
If you have some good photo's I may be able to have a good guess,
John is right about the exhaust I did exactly the same with the Perkins on Taliesin and have done my present boat that way. It's much better than the dry system, quieter and more reliable.
Regards Eric
SeaDog Name (if owner or crew) Ex Taliesin
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Phil
May 23, 2013 - 11:59PM
Re: Propshaft - Advice - update Engines out
John / Eric, thanks for comments.
Yes we are going for a fully wet exhaust. The marine engineer / shipwright who is sorting the placing of the engine and design of the exhaust has decided to run the pipes up into the old Parsons box location as you note but has expressed a concern that once the exhaust gets into the rear cabin that the pipe will be horizontal (i.e. not running down to the transom outlet).
Yes Eric you are correct the MD2040 is a 3 cylinder and consiquently much shorter, (it will even give me room to get at the impeller !) I will take a photo of the actual Engine before it goes in.
Regards - Phil
SeaDog Name (if owner or crew) Soyakaze
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Eric Richardson
May 24, 2013 - 7:17PM
Re: Propshaft - Advice - update Engines out
Hi Phil
The best way to do it is to start with a proper exhaust outlet bend which has a water inlet well below any level which would allow water to splash back into the engine. From this the special fabric exhaust hose should go to a muffler box placed on the engine bearer between the port side of the engine and the port fuel tank. The pipe should then run to a gooseneck fitted where the Parsons box used to be. The discharge from this goes straight into the hose taking it to the exhaust outlet. The inlet to the Gooseneck is so high that waves slapping on the transom can't push water back to the engine. When the engine is running exhaust gases blow the outlet clear even when submerged and of course with the engine off air trapped in the system also holds the water back.
There are some good pictures of how it should be done in the Vetus Catalogue which is available to see on their webb site. I have done this to a few boats and found the Vetus gear OK and not at bad prices.
Dont forget that the water from the engine needs to go to the exhaust outlet via an anti syphon bend mounted as high as possible. On Taliesin I fitted it as John said next to the Gooseneck where the Parsons box was. this is vital to avoid flooding the system when you turn off the engine.
Eric
SeaDog Name (if owner or crew) Ex Taliesin
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