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I am reluctant to name shell builders, but from my research they do still seem to be in business. I really am limited by what the boat owner authorises, like many posters on here, if it were my boat I would tell the world !

Quite right, well remembered ! I never got to see it in the end but some other friends did, and they took a few pictures. Once I obtain copies ( with the boat owner's consent ) I'll post them on here. However, from the images I've seen we were all very very wrong. There is no simple solution, the stern design is out of this world and needs serious metalwork to fix it :- The rounded stern continues below the water line, so there is no swim whatsoever. Looking from the rear the prop and rudder are mounted within a "box" chamber cut into the rounded stern. Each side of the box chamber has a small rectangular channel that goes forward and out to the side of the boat. So, these rectangular channels supply the water to the pop, they are quite small ( hard to estimate dimensions from the image I saw ) so severely limit the water reaching the prop. This is why the boat never picks up speed, no idea about the vibration though. So the next step is to get some quotes to correct it, and decide if it is worthwhile, the boat remains out of the water this week for blacking.

I know sometimes smoke alarms chirp when they are cold, this is a sign the batteries within the device are degrading. One of ours does this overnight when it is cooler, but is fine during the day. I assume this applies to CO alarms as well, do they give a full alarm, or a single chirp indicating low battery ?

Theo / Nick, With the greatest respect we will never convince each other, are somewhat off topic, and probably boring other readers, so let's agree to disagree ! I'll leave the thread to run its' natural course...

Theo, re post#13 ... You are quite right, I should have checked the website first ! I can only assume I was thinking of the Sterling device that claims something similar ? Please feel free to point out the error(s) in my assumptions below. My reasoning for the remainder of my post was that such devices are rated in terms of power, but due to the fixed voltage ( 12v, more recently 14v ) outputs are stated in terms of current to save everyone dividing by the voltage ? If your setup works for then job done, my concern is the alternators are designed to cater for many limitations, heat dissipation being one. I am sure you can eek out a few more watts, but will the cooling be sufficient at the rpm involved ? It seems the Adverc bumps up the output to cater for the assumed voltage drop ? Myself I opted for a 3:1 geared 175A alternator that only gets used over 50% when we run the washing machine. That means it runs cooler and hopefully will last longer ?

Interesting comments, I have never had an alternator with an adjustable regulator. I would suggest modern alternators have much better regulators, how old is yours ? Also, could your symptoms being explained as follows ? The alternator will only supply a maximum power, so the full 100A may only be available with the regulator set to 12.6v ( or some such value. So cranking up the regulator voltage must reduce the max current to keep the power the same. Also, are you happy it is geared to reach max rpm ? The Adverc simply loads your alternator so much it keeps the max current flowing, but the alternator output voltage will be lower than usual, but once again limited to the max power rating of the alternator. The Adverc then provides a regulated output at a higher voltage suitable for battery charging. When you measured the current as 100A with the Adverc, was that the alternator output, or the Adverc output ? So are you saying your batteries charged much quicker with the final setup ? In which case the alternator regulator was poor ( as Nick suggests ). But at the cost of running your alternator flat out for extended periods, maybe limiting its' life ? For the price of both would a modern, high output alternator do the same job ?

Obviously they are batteries, he only has to run his engine once every 25 years ...

Nobody has mentioned it yet so I will ... You could try an ex Black Prince, they sell them off after a few years and would require a few mods to become a liveaboard but would be fine for your needs. Google black prince holidays and check out their site - Personally I would recommend them, the hulls are sound and they are designed for ease of maintenance.

Not so much reluctant, I am away from the boat whilst it is being painted. Will get a chance to see it in 2 weeks time. Sadly I fear modifying the swim would be too expensive ?

Yes there is a cavitation plate that seems ok, whether it is flush with the counter I won't know for 2 weeks. The prop seems fine and the counter is only just in the water, without looking at it I remember the lower rubbing strip is out of the water. The cabin ballast is unknown because there is a proper wooden floor fitted with no inspection hatch. This had led to a build up of water but lets not go there ...

I got caught by the same one twice, having dropped off the first time it sank and waited for me to come around a few weeks later. Eventually removed it and kept it as that's the type we use - firmly fixed, never down whilst cruising. BTW the correct name for them is Linfords...

Thanks guys, sounds like the ballast is the easiest thing to try. The prop is undamaged and fully submerged but not sure by how much. I will have to wait a week or two for the top half to be painted before I can get any pics of the back end out of the water. It does seem the ballast is just insufficient, and the design of the swim is poor, I wouldn't like to post the manufacturers details as it isn't my boat. Will post an update once changes have been tried and tested. Posted Yesterday, 06:57 PM Is the ankar still down? Good point, never thought of this, just assumed it was a pike following us for 2 days !

The boat is now at the yard ready for a repaint, once the top half has been done it comes out for blacking, that's when we'll get to see the detail. In answer to post#22 ( this could be an issue ) :- Qu : How far does the prop shaft extend beyond the end of the swims? Mine only has about a 3" gap between the end of the swims and the forward face of the centre of the propeller. Ans : I did noticed a big gap from the end of the swim to the prop, it is therefore very close to the rudder. Despite the lack of power I was surprised how well it turned, could this be the reason ? The engine runs a treat ( hardly run in ), no play or vibration in the prop shaft.

Qu : Is the counter in the water? Yes, probably only just, I haven't had a chance to take any measurements ( draft, depth to prop etc )

Thanks for the suggestions, my concern is our window of opportunity will soon have been and gone, if it is no better once back into the water that's how it stays for some time ! It also seems I need to clarify a few things :- The boat is only 5 years old and has not done any cruising, in fact it only has delivery mileage on the clock. To the best of my knowledge it has always been like this. The boat was made to order, it appears race horse money was paid for a three legged donkey ! The vibration is only on the tiller, nothing else. I did check every prop blade by hand several times, including the locking nut, then along the prop shaft to the hull but appreciate there is always a chance of missing something - will re-check. The stern is not very low in the water, yet there are already enough ballast bricks in the bilge to build a lock keepers cottage. Adding more sounds a good idea but there isn't any room. My own boat has hardly any ballast in the bilge yet sits lower - how does that work ? Also, the engine seems to be mounted flat, so the prop shaft does not slope down much through the hull, this could be adding to the problem but would be expensive to fix ? The engine and gearbox ( PRM 2:1 ) work fine, you can spin he prop as fast as you like, you don't go any faster, you just get more white water and vibration. How far below the water level should the tip of the prop blade be ? Could we fit a smaller one with a bigger pitch ? As an amusing aside, what did happen was that I became the only person passing moored boats who was told to speed up !

Richard, sorry but I do not understand your question, are you suggesting I have imagined this ? If you are asking about myself, including hire boats, 10 years experience, the last three as a liveaboard on my own boat. Several other helpers have similar experience and although we all have opinions this is not our area of expertise. The quoted speed has been measured and averaged over 2 solid days cruising.

I have just helped move a friends boat for a complete repaint. In doing so I discovered there are major design issues and wondered if a relevant expert could advise of an affordable solution ? It is a seventy footer with an isuzu 42BHP engine. The transmission works perfectly and the prop spins a treat but...The boat has a maximum speed of 1 ( one ) mph. The prop seems to produce plenty of "white water", when pushed water spurts out above the water level. Also, despite the tiller bearings having no play the vibration is extreme, jumping randomly from side to side as you try to go straight. It is so bad when trying to exit any lock it has to be pushed to start moving regardless of the revs. I have checked the weed hatch and the prop is clear, the prop shaft extends a long way out of the hull to be very close to the rudder, the prop is undamaged and seems to be a typical size ( 16 inch diameter but not yet measured ). Other observations are that the boat seems level ( it does not slope down towards the back ), the "swim" is very rounded, and the engine is mounted level so the prop shaft has a very shallow angle down through the hull. The boat comes out of the water soon and we will have a chance to have a good look under the water level. But this is also a chance to improve things, can anyone suggest an affordable solution to improve it please ?

The warning shows a mis-match between the generator and the inverter, so as previously mentioned checking the live neutral swap is the best bet. However, there is also a slim chance it is your boat that has been swapped. Does your boat work ok with a shoreline ? Could you try your generator on a friend's boat ? Or their generator on yours ? These tests should tell you where the fault lies.

I believe the engine "earth strap" is to avoid the current finding a return path that perhaps wouldn't be obvious ( such as those mentioned above ). I remember years ago it would be the choke cable on a car engine that would get hot. So I am now thinking I should remove the -ve from the alternator to the hull and run it to the battery -ve directly. Previous posts asking about the potential return path, what about DC bonding to the hull ? I am unsure how the mains earth, 12v -ve, and GI combine to connect to the hull.

To Quote the last post :- So if I have a length of copper wire in parallel with a great big lump of steel and there is 100 amps flowing from one end to the other no current will flow through the steel? That's what I am struggling with, I could ( and probably will ) run a dedicated -ve from the battery bank to the alternator body ( where it is currently strapped to the hull ). I think this will reduce the current through the hull but not eliminate it, and even if it is a small percentage ... out of 100A that is still a lot ! Surely other people have a current flowing from their "earth straps" ? Which still leaves me confused about the answer to the original question ! Having the boat blacked at present and the anodes look fine, with minimal pitting ( for the age ) so it does seem to be harmless - hmmmm

Well, on my high output alternator about 10% of the current returns via the hull. I do have a -ve from the battery to the engine, and the alternator is not of the isolated type. But there is another -ve from the alternator to the hull, which I was told was normal. ( I believe this is to avoid high currents through the propshaft, or mechanical cables etc ? ) The clamp meter typically shows say 40A output on the alternator +ve, and 4A on the -ve from the hull, therefore 36A returning via the intended -ve via engine / alternator mounting. I have wondered whether to try and reduce / eliminate this 4A but wondered what the general situation was ?

The use of an earth return for onboard electrical equipment is discouraged as it is a potential source of hull corrosion ? YET most of us use high power alternators with exactly that, so what's the difference ? If a few mA from a radio will cause damage, think what 100A will do !

Just to throw another spanner in the works. If you change individual batteries out of a bank, even if they are the same type you may also have ( a similar ) problem... If the existing batteries are old and have lost some capacity you effectively have a bank of different Ah rating batteries -discuss ! Ideally change them all as a bank.

Paul, In addition to the suggestions above, after a 5 hour cruise the batteries should have been charged up nicely, if they are not it suggests an alternator / wiring / charger switch issue as well. Sounds like you need to get someone to take a look as it is incredibly hard to accurately diagnose "unseen". Did you get the previous owner to give you a run-through of all on board systems, and do you have any manuals ?

Well, you pay your money and take your choice / chance ... Allegedly Chinese products have fake "CE" marks ( European safety approvals ), which can be potentially dangerous. Search the web for an explanation, often they claim it stands for China Export but looks remarkably similar to the proper CE mark. On our marina in the last year there have been 2 inverter fires, don't know the details but ...Generally in life you get what you pay for and don't forget if it seems too good to be true, it probably is ! The same goes for Chinese MPPT controllers, and has been in the news in recent years phone / laptop chargers catching fire ( the cheap imitations more so than the OEMs ).