Re: "ISOLATED GROUND" for Main engines and generators

Marco Mancini

Bill thanks for your answer. 
we are aware of the problem and our mechanic as well. All the engine frame and the head of C transmission are  connected to the ground cable. The issue now is that the sensors on yanmarr 4jhlte  are connected with the engine CPU and we are understanding how solve the problem.
In any case we have the Anode on the h6 autoprop and also on the rudder. 

Il giorno 14 lug 2020, alle ore 16:15, CW Bill Rouse <brouse@...> ha scritto:

I changed the subject of this thread. I answered Marco below. Anyone else reading this thread, please note that this mistake is commonly made by yards and mechanics changing engines. It can also happen when a mechanic "repairs" a "no-start problem." Many "no-start problems" are the result of a failed 12-volt negative solenoid, which is part of the Isolated Ground system. I know of too many situations where the mechanic by-passed this solenoid, invalidating the Isolated Ground system.

Marco, no I do not have a schematic of the Amel Bonding (yellow/green wire). Also, it is important to note, that Amel refined and changed this wiring and what was connected over many years with many changes. This bonding wiring schematic was not documented in any detail until the Amel 50 manual, which seems to be very complete and designed in such a way that a novice can understand most of the detail.

When discussing this with your mechanic, it may be useful to tell him that the Amel Bonding system and the Main Engine and Onan Isolated Ground (12-volt Negative) is similar to what many boat builders use when producing an aluminum boat to prevent the aluminum hull. from disintegrating from electrolysis. You will know that you have the wrong mechanic if he tells you that this is not necessary. If he installed a non-isolated ground engine, I believe that you should make changes to the 12-volt connections engine, and until you do make changes, you should maintain a good anode on the propeller as well as the rudder.

CW Bill Rouse Amel Owners Yacht School
Address: 720 Winnie, Galveston Island, Texas 77550 
View My Training Calendar

On Tue, Jul 14, 2020 at 1:27 AM Marco Mancini <marcomancini61@...> wrote:
Dear Bill thanks a lot for your valuable  information. I will go thought with the mechanic it and I let you know. 
Do you have a schemE of the SM GROUND LINE, I MEAN the cable that  connect all the metallic objects on board and that end up on the rudder axis? 
I don’t remember if in the  engine compartment the ground line  exist as a wire  or it is substituted by the steel frame on which is ploughed the engine and then the ground line  continue as a wire in the aft cabin untill the rudder axis . 
On the other hand I remember that the aft keel bolt , the C transmission are connected to the engine frame. Do I remember exactly ?
really thanks for your support . It will be a pleasure sailing with you in the Naples Bay . 

Il giorno 13 lug 2020, alle ore 14:53, CW Bill Rouse <brouse@...> ha scritto:


I attached a page from my Amel Book which my answer your question. If not, email me at brouse@...


CW Bill Rouse Amel Owners Yacht School
Address: 720 Winnie, Galveston Island, Texas 77550 
View My Training Calendar

On Sun, Jul 5, 2020 at 4:46 PM Marco Mancini <marcomancini61@...> wrote:
Bill it is nice to have your comment . 
I have to check for this .
What do you mean ? I think I don’t have sufficient knoweldge about your question.  May please provide me additiional info ? 
as you may image we carry 2 alternators one for the 12 volt engine / onan battery charger ant another one at 24 volt for the other batteries. 

Il giorno 05 lug 2020, alle ore 21:30, CW Bill Rouse <brouse@...> ha scritto:

Did your mechanic Isolate the 12-volt negative? 
CW Bill Rouse Amel Owners Yacht School
Address: 720 Winnie, Galveston Island, Texas 77550 
View My Training Calendar

On Sun, Jul 5, 2020 at 1:10 PM karkauai via <> wrote:
Hi Marco,
Are you still using the AutoProp H6 with the new engine?  If yes, did you have it modified in any way?

SM 243

On Jul 5, 2020 1:18 PM, Marco Mancini <marcomancini61@...> wrote:

the TMD22 with the mechanical gearbox (2,8 reduction factor) and the autoprop h6 was probably  never reached in our 20 years of SM  more than 2500 2600 rpm ,
The TMD22 engine characteristic curve show that the 78 hp ( the max power) is obtained at 3500 - 4200 rpm  but at 2500 the curve show 40 hp and the boat has never reached more than 7.5 knots 
Now we have moved to the yanmar 110 cv,  the new version of the yanmar 100) with gearbox with 2.3 rduction factor   (midway betwenn the 1.97 of amel 54 with 110 volvo and  2.8 of the yanmar 100 )  that is  the new version  of the well known  Yanmar 100 cv  installed by Amel  after the TMD22. In Italy due to a severe restrictions of  omologation certificate we had also to afford the cost of new homologation certificate but we hare happy with this change . indeed the boat seems to go much better, it has a cruise speed of 8,5  at 2300 rpm over 3200rpm ( max engine regime)  and also in the manoeuvres she is more prompt than before . 
cheers and good wind . 
marco mancini 
SM 304 

Il giorno 25 giu 2020, alle ore 16:55, Thomas Peacock <peacock8491@...> ha scritto:

This is question without a definitive answer. 
We also have the TMD22. When we bought our boat (about 4 years used), we could get almost 3,000 rpm at max throttle. Our local diesel guy suggested cruising at 80% of max, or 2,400. Our max started to lessen within about a year. 
Ever since then, we have usually not been able to max out at 3,000. Usually max is 2,400 to 2,600, so we cruise at 80% of that.
Issues affecting max cruise rpm include bottom, prop (even one barnacle can make a difference), turbo condition, and countless others. 
I suppose that, just like me, the Volvo has also lost a little mojo as it has aged. 

Tom Peacock
SM 240 Aletes
Chesapeake Bay

with its tiny keyboard

On Jun 25, 2020, at 10:10 AM, JOSE PRIETO <prietomd11@...> wrote:

Hello Amelians!  I am in the process of learning my boat.  The engine is a Volvo TMD22, with autoprop h6 propeller.
I found some threads here on the forum related to this topic, but none conclusive about what is the ideal cruise rpm regime, and what is the maximum rpm?  I can't get more than 2100 rpm!
 Any suggestion?

Jose Prieto
SV Wayag, SM 323
Currently Alicante, Spain

<Amel Isolated Ground (12DC Negative) Engines and Generators.pdf>

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