nigelmercier
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Yes, sorry I realised and changed my post. I've actually spent some time making the schematic more readable, so I'll post it when I have access.
Volvo Penta Saildrive isolation: how?
- Thread starter nigelmercier
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nigelmercier
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See below ...
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nigelmercier
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OK, here they are:
MD22P Engine Wiring Diagram
MD22P Instrument Panel Wiring
I've been looking at my version of the schematic, and I'm not sure it is correct. The diagram I downloaded is very ambiguous in one area:
According to DIN 72 552, terminal 31 should be "Return line to battery - battery terminal or ground, direct", but does the wire from the negative breaker above actually go to the starter motor terminal 31, or just pass very close?
In actuality, it does; there is a 95mm² wire going from the ground terminal on the engine mount direct to the starter motor, with 3 other black wires on the same terminal, I don't see how this could be isolated.
MD22P Engine Wiring Diagram
MD22P Instrument Panel Wiring
I've been looking at my version of the schematic, and I'm not sure it is correct. The diagram I downloaded is very ambiguous in one area:
According to DIN 72 552, terminal 31 should be "Return line to battery - battery terminal or ground, direct", but does the wire from the negative breaker above actually go to the starter motor terminal 31, or just pass very close?
In actuality, it does; there is a 95mm² wire going from the ground terminal on the engine mount direct to the starter motor, with 3 other black wires on the same terminal, I don't see how this could be isolated.
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VicS
Well-Known Member
I think I understand it although the little grey cells are are buzzing round in circles now.
I think ( as you confirm in reality) that the SB cable from the negative isolator must in fact be connected to terminal 31 as well as what ever else it is connected to.
I think the starter motor itself is an insulated one ... ie does not use the engine block for the negative return. The SB cable from the negative isolator must go to a negative terminal as well as to 31.
When the glowplugs are energised or when the key is turned to the stop position the earthing relay is energised and earths the block to that these can operate.
Different to the 2010 series is as much that there is a negative connection direct to the starter motor. They have a heavy duty solenoid instead of the relay which forms the negative connection for the starter as well as the other items. Its mounted on bracket near the starter motor.
It costs over 200Euros so you can imagine the gnashing of teeth and the search for an alternative when it fails
Still a puzzle though as to what the cable you have on the engine mount is.
Is it actually connecting the block to DC negative? It defeats the object of the isolated system if it does.
Not something added thinking it was connecting the sterngear to a hull anode ?
scottie
Well-Known Member
I would suggest that wire SB does not go to 31 but to another unlabelled terminal
Remember the additional solenedoids are to temporary allow the earth to be through the engine block to suit earth return starter and stop solenoid only whilst being operated.
Remember the additional solenedoids are to temporary allow the earth to be through the engine block to suit earth return starter and stop solenoid only whilst being operated.
VicS
Well-Known Member
I thought at first that it did not also go to 31 but if it does not how does all the rest of the electrics get a negative connection... It is the only wire that is connected to battery negative ! If its not connected externally it must be connected internally
Nigel says he has confirmed that in reality it is connected to 31
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fastjedi
Well-Known Member
Some related observations / questions ....
1. My saildrive anode appears to play no part in protecting my propeller. When the propeller anode is gone the propeller is the next thing to erode despite being within mm's of a perfectly fine saildrive anode. I haven't checked the continuity between the shaft and the saildrive case or anode (yet) but it is hard to beleive they are electrically isolated, and if there are I cant imagine I could effect a change?
2. A similar boat, with a similar Volvo saildrive, with similar propeller in the boatyard doesn't have a propeller anode (Early versions on the Volvo propeller hub didn't accomadate anodes) .... and is perfectly fine. (Although it does have a ropecutter, perhaps that provides a path?)
3. If I epoxy and antifoul most of the propeller so a much smaller surface area is exposed, would damage potential reduce / would my propeller anode last longer ..... or does the anode erode at a given rate regardless of what it is protecting?
1. My saildrive anode appears to play no part in protecting my propeller. When the propeller anode is gone the propeller is the next thing to erode despite being within mm's of a perfectly fine saildrive anode. I haven't checked the continuity between the shaft and the saildrive case or anode (yet) but it is hard to beleive they are electrically isolated, and if there are I cant imagine I could effect a change?
2. A similar boat, with a similar Volvo saildrive, with similar propeller in the boatyard doesn't have a propeller anode (Early versions on the Volvo propeller hub didn't accomadate anodes) .... and is perfectly fine. (Although it does have a ropecutter, perhaps that provides a path?)
3. If I epoxy and antifoul most of the propeller so a much smaller surface area is exposed, would damage potential reduce / would my propeller anode last longer ..... or does the anode erode at a given rate regardless of what it is protecting?
Stork_III
Well-Known Member
Do you have a folding prop. If so the shaft is isolated from the hub by the pressed rubber bush holding the splines into the hub. Whether this is an electrical isolation as well, I'm not sure, but may explain the non-protection to the prop offered by the leg anode
VicS
Well-Known Member
I am pretty confident that you will find continuity between the shaft and the sail drive leg. It may not be good as it will be through bearings that are coated with oil.
A rubber hub will insulate the prop.
incorrectly fitted rope cutters might bridge the insulation of the hub
Epoxy coating of the prop should effectively reduce the area in contact with the water and ought to extend the anode life... lets us know at the end of next summer by how much
nigelmercier
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If such a thing exists, my thinking goes out of the window. I assumed that the engine was grounded via the starter motor. I will have to investigate further.
scottie
Well-Known Member
There are isolated return starters about and Volvo do use them but I don't recall if they were used on MD22
I am still convinced that they were earth return as being automotive origin.
One clue would be to look for a heavy cable suitable for starter loads and where it is connected if direct to starter that would be a fair clue that it is an insulated starter.
I am still convinced that they were earth return as being automotive origin.
One clue would be to look for a heavy cable suitable for starter loads and where it is connected if direct to starter that would be a fair clue that it is an insulated starter.
VicS
Well-Known Member
Also go back and read Playtimes post. He had an MD22 !
http://www.ybw.com/forums/showpost.php?p=3963247&postcount=16
http://www.ybw.com/forums/showpost.php?p=3963247&postcount=16
Playtime
Well-Known Member
My engine was an MD22L but the wiring diagram is the same as those already posted above.
The attached photo below shows the starter with 2 heavy duty cables connected, positive to the solenoid on the top and the (blue tape) negative direct to the starter itself i.e. the starter is insulated from the block. Otherwise why would Volvo provide the third (earthing) relay in the control box?
I say again, Nigel, I think you have an ill advised mod to your starter wiring. Maybe your starter was replaced with a (much cheaper) earth return (automotive) type and the wiring modified accordingly.
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VicS
Well-Known Member
And the one in your photo looks pretty much like the diagram in the parts list.
888 Euros would explain why a non insulated one has been fitted if that is what has been done!
888 Euros would explain why a non insulated one has been fitted if that is what has been done!
nigelmercier
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As I said, if the starter is insulated, then my assumptions are wrong. My wiring looks identical to your wiring, my starter, your starter...
Playtime
Well-Known Member
So what is the purpose of the wire to the engine mount?
nigelmercier
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It is just a junction point, it doesn't connect to the engine. I assumed this was standard, didn't think it would throw up a red-herring.
It is possible that the engine is getting grounded by the secondary 24V alternator, I need to check. If so, I will probably isolate it using a relay, so it is only grounded when the ignition is on.
[Later] The 24V alternator has two B terminals, so may also be isolated. I'm going out in a few weeks, so I'll report back.
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Playtime
Well-Known Member
haydude
Well-Known Member
Not just sometimes, ALWAYS AND ABSOLUTELY. If they are not following a test, something has gone wrong.
TRUNDLETRUC
Well-Known Member
Saildrive insulation
Returning to the original thread-
Later Volvo engines (D1 30 and 130s saildrives) have the insulation between the bell housing and the saildrive rather than between the engine and bell housing. Therefore no insulation washers on the engine bell housing bolts.
One area that is often overlooked concerning the insulation is the control cables. The cable for gear operation (on top of the saildrive) has no insulation therefore there is electrical connection with the morse controller in the cockpit. The cable from this that controls the throttle is usually insulated where it joins the engine (rubber washer).
It is important that no connection is made between the morse controller and steering mechanism which through the rudder shaft will complete a circuit with the sea water. Also make sure there is no electrical contact between morse controller/cables that link to the engine.
Check with an ohm meter.
Returning to the original thread-
Later Volvo engines (D1 30 and 130s saildrives) have the insulation between the bell housing and the saildrive rather than between the engine and bell housing. Therefore no insulation washers on the engine bell housing bolts.
One area that is often overlooked concerning the insulation is the control cables. The cable for gear operation (on top of the saildrive) has no insulation therefore there is electrical connection with the morse controller in the cockpit. The cable from this that controls the throttle is usually insulated where it joins the engine (rubber washer).
It is important that no connection is made between the morse controller and steering mechanism which through the rudder shaft will complete a circuit with the sea water. Also make sure there is no electrical contact between morse controller/cables that link to the engine.
Check with an ohm meter.
