Marine Starter Motors???

[PaulRainbow]

when you highlighted my original post, you conveniently omitted highlighting the word “technically”

you might not need to change anything, depending on the modifications. A non insulated alternator or starter might make the connection between case and existing return cable.

in post #27 you said "My Volvos have isolated earth senders, starters and I dare say the original alternators were. "

Are you saying that you have changed the alternators for non isolated return versions and that they work ok ?

 

[dragoon]

So if we eliminate the risk of brush spark on a starter motor then maybe we should ignition protect all our DC switches and contactors on board.

I’m not sure I fully understand your question.....but if they’re in the bilge where gas can build up undetected then you might want to give it some thought.

 

[dragoon]

in post #27 you said "My Volvos have isolated earth senders, starters and I dare say the original alternators were. "

Are you saying that you have changed the alternators for non isolated return versions and that they work ok ?

I‘m not saying anything, but as I’m not sure without testing them so I made that statement . They were replaced at some point, but I recall discussion with Volvo about a part number and design change together with an upgrade to output. Without going down there with a multimeter I don’t actually know.

 

[Refueler]

Not on any engine I’ve ever owned.

I‘m aware it’s the case on a few models, but it’s hardly common, let alone the norm.

Pete

Especially given that most marine engines come from vehicle or land based engine designs.

 

[179580]

I’m not sure I fully understand your question.....but if they’re in the bilge where gas can build up undetected then you might want to give it some thought.

It was not a question. I will try to elaborate. A motor or indeed any rotating machine with a brush and a commutator will produce some sparking. Indeed in the case of a start motor you have the added risk on the actuation of the solenoid. In certain circumstances, for example, trucks used to transport petroleum products have to not only have the motors ignition protected but the whole DC system including an insulated negative. The low current switching is also a risk due to contact arching which tends to be longer on a DC system. To worry about this on a leisure boat, I believe, is a little OTP as more of a risk is perceived by making and breaking your domestic switches or lighting the stove or your pipe.

 

[dragoon]

It was not a question. I will try to elaborate. A motor or indeed any rotating machine with a brush and a commutator will produce some sparking. Indeed in the case of a start motor you have the added risk on the actuation of the solenoid. In certain circumstances, for example, trucks used to transport petroleum products have to not only have the motors ignition protected but the whole DC system including an insulated negative. The low current switching is also a risk due to contact arching which tends to be longer on a DC system. To worry about this on a leisure boat, I believe, is a little OTP as more of a risk is perceived by making and breaking your domestic switches or lighting the stove or your pipe.

That makes sense, but boat and boat part manufacturers do take this into consideration. Additional risk mitigation is included by adding detection, alarms and auto cut off for LPG systems. I’m not sure as much consideration goes into switch equipment above floor level though. But surely this is a result of the long held convention that flammable gases are heavier than air and tend to collect in the bilges where they can build into dangerous concentrations ? Whether right or wrong I have no idea.

 

[PaulRainbow]

I‘m not saying anything, but as I’m not sure without testing them so I made that statement . They were replaced at some point, but I recall discussion with Volvo about a part number and design change together with an upgrade to output. Without going down there with a multimeter I don’t actually know.

I'll save you the trip with your multimeter.

Non insulated starter motors and alternators have their negative connections made to their cases. The case is bolted to the block and the block has a negative return cable to the vessels DC negative. If you fit one of these to an insulated return engine it will not work because the negative return does not exist.

In post #37 you say "you might not need to change anything, depending on the modifications. A non insulated alternator or starter might make the connection between case and existing return cable. "

If you have isolated return engines there is no "existing return cable". If someone fitted non insulated return alternators and connected a negative cable to them, your engines are no longer isolated return.

EDIT: On second thoughts, try a continuity check between your engine blocks and the battery negatives, you'll know then for sure if your engines are still isolated return, or not.

 

[dragoon]

I'll save you the trip with your multimeter.

Non insulated starter motors and alternators have their negative connections made to their cases. The case is bolted to the block and the block has a negative return cable to the vessels DC negative. If you fit one of these to an insulated return engine it will not work because the negative return does not exist.

In post #37 you say "you might not need to change anything, depending on the modifications. A non insulated alternator or starter might make the connection between case and existing return cable. "

If you have isolated return engines there is no "existing return cable". If someone fitted non insulated return alternators and connected a negative cable to them, your engines are no longer isolated return.

EDIT: On second thoughts, try a continuity check between your engine blocks and the battery negatives, you'll know then for sure if your engines are still isolated return, or not.

By return cable I meant the negative feed from the component back to the battery.

My alternators do have a negative post on them which I would have connected. I’m not sure that this means in all cases that they are insulated earth though. I replaced a Landy alternator recently and recall there was a post that had connectivity to the case - being a car though, there was no negative lead on the loom to connect.

I’ll test the continuity to earth at some stage - I recall going round this loop many years ago, with guidance from Volvo at the time. It’s low on the list at the moment as they work and I’ve not noticed increase engine anode consumption or corrosion, so have come to the conclusion that things are in an ambient state.

The next jobs on the list are varnishwork, but she needs to come out of the water and go under cover to do this properly.

 

[PaulRainbow]

By return cable I meant the negative feed from the component back to the battery.

My alternators do have a negative post on them which I would have connected. I’m not sure that this means in all cases that they are insulated earth though. I replaced a Landy alternator recently and recall there was a post that had connectivity to the case - being a car though, there was no negative lead on the loom to connect.

I’ll test the continuity to earth at some stage - I recall going round this loop many years ago, with guidance from Volvo at the time. It’s low on the list at the moment as they work and I’ve not noticed increase engine anode consumption or corrosion, so have come to the conclusion that things are in an ambient state.

The next jobs on the list are varnishwork, but she needs to come out of the water and go under cover to do this properly.

You still seem a little confused. With an insulated return system there are no connections to the block, each component has a separate return. In the case of sensors they are all two wire versions, the case is completely isolated. In the case of the starter and alternator the case is also isolated, so it needs a negative connection to the B- terminal. You can fit an isolated return starter or alternator to a non isolated engine by connecting a cable from the B- terminal to the engine block, VP do this with some of their MD series engines (amongst others no doubt). But, you cannot fit a non isolated starter or alternator to an isolated return engine, because there is no negative connection to the block there is no negative return. You could connect a negative cable to the starter or alternator case and it would work, but the engine would no longer be isolated and would not be connected to an anode, which would obviously be risky.

Good luck with the varnish.

 

[dragoon]

You still seem a little confused. With an insulated return system there are no connections to the block, each component has a separate return. In the case of sensors they are all two wire versions, the case is completely isolated. In the case of the starter and alternator the case is also isolated, so it needs a negative connection to the B- terminal. You can fit an isolated return starter or alternator to a non isolated engine by connecting a cable from the B- terminal to the engine block, VP do this with some of their MD series engines (amongst others no doubt). But, you cannot fit a non isolated starter or alternator to an isolated return engine, because there is no negative connection to the block there is no negative return. You could connect a negative cable to the starter or alternator case and it would work, but the engine would no longer be isolated and would not be connected to an anode, which would obviously be risky.

Good luck with the varnish.

I’m not getting confused, honestly . Electronics has been my career path for over 25 years.

I agree with your statements, except that it’s possible to have an alternator with a negative terminal that is connected to the frame of the alternator. In this case, if the existing return is connected to that terminal, the engine is now connected to negative, but eveything will operate fine. Whether this matters now depends on many other factors, such as flow of current via parts of the engine where there are mixed metals, and provision for other galvanic protection such as internal and external anodes.

back to the OPs original question, where they asked if there was a difference between a marine starter motor and non starter motor. Yes, there can be. Electrical insulation and spark reduction are two areas I’m aware of. If it saved me £700 to fit the non marine version, would I do so? Maybe, but I would encourage anyone to give it some thought before doing so.

 

[thinwater]

Particularly on trucks, allows use to the ADR regs. Carriage of inflammable liquids etc.

There is no such thing as an inflammable liquid in current ISO, DOT, UK Transport, or ASTM language. It is an archaic usage and is not used on labels or in fire codes. They are flammable liquids.

Purge it from your lexicon, like irregardless.

 

[PaulRainbow]

I’m not getting confused, honestly . Electronics has been my career path for over 25 years.

I agree with your statements, except that it’s possible to have an alternator with a negative terminal that is connected to the frame of the alternator. In this case, if the existing return is connected to that terminal, the engine is now connected to negative, but eveything will operate fine. Whether this matters now depends on many other factors, such as flow of current via parts of the engine where there are mixed metals, and provision for other galvanic protection such as internal and external anodes.

back to the OPs original question, where they asked if there was a difference between a marine starter motor and non starter motor. Yes, there can be. Electrical insulation and spark reduction are two areas I’m aware of. If it saved me £700 to fit the non marine version, would I do so? Maybe, but I would encourage anyone to give it some thought before doing so.

I've already said, several times, if you do this the block is then no longer isolated, although the alternator will obviously work.

It totally contradicts your opening statement of "Marine engine electrical accessories technically should all be of the insulated earth type and not have a negative feed via the case or chassis."

After arguing for several posts you now say "Whether this matters now depends on many other factors, such as flow of current via parts of the engine where there are mixed metals, and provision for other galvanic protection such as internal and external anodes."

You really need to make your mind up.

Connecting such an alternator to an isolated installation is a bad idea. It's either isolated, or it isn't, no mixing no insulated equipment on an insulated engine.

 

[fushion julz]

Yes, of course, a spark on a boat will cause i giant explosion.

What nonsense.

It isn't nonsense...It's a fact...the starter motors are different. It may not cause an explosion, but LPG is heavier than air and sinks to the bottom of the bilge. A spark in the engine bay, even on a diesel boat has the potential to cause an explosion. I had nothing to do with the design, but it makes sense to me...Now MY boat has a diesel engine and no gas on board (other than a couple of small canisters for a camping stove). Still, I'm happy someone at Perkins (and presumably Fairey) as well as the MoD (where the boat was originally, when new) specified minimizing any potential risk.

 

[Refueler]

I am not decrying the safety aspect of preventing sparks of any kind .. and ensuring safety with gas etc.

But given the number of boats around with gas .. petrol etc on board .... I dare to suggest that number of spark igniting gas fires / explosions on boats is phenomenally small number.

I agree that the consequences of a Gas ballon going up is catastrophic ... I am aware of the boat at Hayling Island ... but how many have due to engine spark related ? Lets discount those that have gone up due to other causes .... unrelated to the topic here.

 

[dragoon]

I've already said, several times, if you do this the block is then no longer isolated, although the alternator will obviously work.

It totally contradicts your opening statement of "Marine engine electrical accessories technically should all be of the insulated earth type and not have a negative feed via the case or chassis."

After arguing for several posts you now say "Whether this matters now depends on many other factors, such as flow of current via parts of the engine where there are mixed metals, and provision for other galvanic protection such as internal and external anodes."

You really need to make your mind up.

Connecting such an alternator to an isolated installation is a bad idea. It's either isolated, or it isn't, no mixing no insulated equipment on an insulated engine.

I don't need to make my mind up - it's the manufacturers. Where salt water and mixed metals are present, the best is to avoid the passage of electrical current - this is fact.

When a manufacturer chooses to go down the route of isolated earth or not, or to make some of the components isolated earth, but not others, I don't choose this. My guess is they do this with consideration as to what current will pass, how frequently by what route, what protections are in place and what is likely to be corroded.

However, if an owner makes the choice to switch out something spec'd for the marine version of the engine engine with something that the manufacturer specifically had to upgrade from it's base design, they should be armed with the facts and make an informed decision. They should be asking "why was it made this way?"

So let's go back to my VP engine design and installation - I know it originally had components that were isolated earth. However, I know there are some parts (temp sensor and overhead sensor) that are not, and never were. I know it is bonded back to earth, via at least the external anode circuit, but there may be other routes. I am fairly confident the original alternators were isolated earth, I am not so sure about the replacements that superceded the original design.
So Volvo introduced a set up that is hybrid in some way, both from when it was new, and since through part superceding.

Again, I don't need to make my mind up. The OP should be aware there are specific marine variations of parts though, and they are done for a reason.

 

[fushion julz]

how many have due to engine spark related ?

Maybe few because of the safety of the electrical systems

 

[Refueler]

Maybe few because of the safety of the electrical systems

Aw c'mon .... given the number of boats around with owners DIY work on them ... marinised land engines ... etc. etc.

Not everyone has a Bavaria Wiring loom in their boat etc.

 

[Tranona]

Maybe few because of the safety of the electrical systems

The reality is that gas explosions are extremely rare on yachts because they are mostly diesel powered and gas systems very reliable. While there is always the possibility of explosions IF there is a leak AND a spark from the starter motor, the chances of these two happening together is vanishingly small. Contrast this with, for example the US where explosions and fires on boats are more common - but only because of the huge number of petrol powered boats.

While it is important to take into account theoretical possibilities with regard to adverse events when designing systems it is also important to take note of empirical data around such events to assess the probability of such events occurring.

 

[PaulRainbow]

I don't need to make my mind up -

You most certainly do.

So let's go back to my VP engine design and installation - I know it originally had components that were isolated earth. However, I know there are some parts (temp sensor and overhead sensor) that are not, and never were. I know it is bonded back to earth, via at least the external anode circuit, but there may be other routes. I am fairly confident the original alternators were isolated earth, I am not so sure about the replacements that superceded the original design.
So Volvo introduced a set up that is hybrid in some way, both from when it was new, and since through part superceding.

In post #22 you said "Marine engine electrical accessories technically should all be of the insulated earth type and not have a negative feed via the case or chassis. "

In post #27 "My Volvos have isolated earth senders, starters and I dare say the original alternators were. "

You now say it's bonded to Earth and has sensors that are not isolated return, therefore you engines are NOT isolated return.

 

[PaulRainbow]

It isn't nonsense...It's a fact...the starter motors are different. It may not cause an explosion, but LPG is heavier than air and sinks to the bottom of the bilge. A spark in the engine bay, even on a diesel boat has the potential to cause an explosion. I had nothing to do with the design, but it makes sense to me...Now MY boat has a diesel engine and no gas on board (other than a couple of small canisters for a camping stove). Still, I'm happy someone at Perkins (and presumably Fairey) as well as the MoD (where the boat was originally, when new) specified minimizing any potential risk.

Still nonsense to suggest that diesel powered boats need ignition protected starters. You cannot ignite diesel with a spark from a starter motor. If a boat has LPG onboard it's far better (and more usual) to fit gas alarms, rather than rely on an ignition protected starter, what happens if you don't use the engine for a few days when you're onboard and LPG is leaking into the bilges ?

Ignition protected starters are normally fitted to petrol boats, not diesels. Yours is an exception, not the norm. It was not fitted as standard by Perkins, or Fairey, it was fitted as part of the MoD spec (a fact you omitted to reveal in your original post. It was fitted because the MoD were paranoid about gas explosions, they managed to blow a Nic' 52 up with LPG after a catalogue of errors and a badly designed system, leading to the generator igniting LPG in the bilges.