Marine Starter Motors???

[Sybarite]

Hello

I am a basic mechanic and can normally get there at the end of the day. Is there really any difference between a "Marine" Starter motor and an ordinary agricultural one except of course price.
I would have thought a starter motor is a starter motor is a starter motor. The difference in price between Volvo parts and JCB is staggering. Am I missing something or is a "Marine" thing.

Sean

Two or three years ago I had to replace my starter motor on a VP2002. A diesel mechanic said that they were horribly expensive - probably about €900 but he could get me one he hoped for about €500. I called into the Volvo concessionnaire who told me that they were €1400...

I bought a new one over the net from a firm near Manchester for £60. It was delivered two days later. It has worked 100% since then.

 

[dragoon]

Some marine starter motors and alternators are insulated return. That isn't common on industrial ones AFAIK.

That’s what i understood too. Marine engine electrical accessories technically should all be of the insulated earth type and not have a negative feed via the case or chassis.

 

[prv]

That’s what i understood too. Marine engine electrical accessories technically should all be of the insulated earth type and not have a negative feed via the case or chassis.

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

 

[PaulRainbow]

That’s what i understood too. Marine engine electrical accessories technically should all be of the insulated earth type and not have a negative feed via the case or chassis.

That's utter nonsense.

 

[Gwylan]

Hello

I am a basic mechanic and can normally get there at the end of the day. Is there really any difference between a "Marine" Starter motor and an ordinary agricultural one except of course price.
I would have thought a starter motor is a starter motor is a starter motor. The difference in price between Volvo parts and JCB is staggering. Am I missing something or is a "Marine" thing.

Sean

The colour of the paint.

 

[PaulRainbow]

The starter on my Perkins T6.354 is different to the ones used on the agricultural versions. The marine one has a concentric solenoid integral to the starter housing. This minimises the risk of a spark on operation.

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

What nonsense.

 

[dragoon]

That's utter nonsense.

I didn’t say they all do it, but it’s not nonsense, it’s done to limit galvanic corrosion in some installations . My Volvos have isolated earth senders, starters and I dare say the original alternators were.
I also understand that marine grade alternators are often fitted with stainless bearings.

 

[Laminar Flow]

I didn’t say they all do it, but it’s not nonsense, it’s done to limit galvanic corrosion in some installations . My Volvos have isolated earth senders, starters and I dare say the original alternators were.
I also understand that marine grade alternators are often fitted with stainless bearings.

I'm afraid that is not true either. Even on aluminium boats it has been proven that a non- isolated ground makes no difference to galvanic corrosion; much in the same legue as the infamous copper penny in the bilge..

 

[PaulRainbow]

I didn’t say they all do it, but it’s not nonsense, it’s done to limit galvanic corrosion in some installations . My Volvos have isolated earth senders, starters and I dare say the original alternators were.
I also understand that marine grade alternators are often fitted with stainless bearings.

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.

Sorry, that's nonsense.

The vast majority of marine engines do not have isolated returns. Volvo fitted some that were, most notably sail drive engines, yet other manufacturers fitted engine/saildrive combinations without isolated returns and they didn't all dissolve due to galvanic corrosion. There are millions of boats with non insulated returns and Volvo build a huge amount of engine/sterndrive combinations that were not isolated. Just because Volvo dream something up does not mean that it's true and it's incorrect to say that "Marine engine electrical accessories technically should all be of the insulated earth type"

 

[dragoon]

I'm afraid that is not true either. Even on aluminium boats it has been proven that a non- isolated ground makes no difference to galvanic corrosion; much in the same legue as the infamous copper penny in the bilge..

When I’ve replaced the senders and oil pressure switches on my VP 40s I was advised I needed to use genuine two pole switches that were earth insulated. This is what was fitted by the manufacturer. I’ve seen them with my own eyes and researched the point of them at the time. These are still the official part that can be readily purchased from VP.
I don’t doubt that this may not be the case on all installations. Like choosing to bond seacocks or not, galvanic action is a complicated subject as it’s subject to many factors. Boat engines also use a lot of different metals, so independent of the hull material have a lot of scope for galvanic activity.
I‘m sure every engine is different and things will vary by installation. However if you already have a truly earth insulated installation, have never suffered a galvanic problem, and you now change that by replacing one part that provides a path to earth, it’s useful to consider that before making that decision.
Also an engine that is insulated from earth, now connected via a single low current link, may discover that path is used inadvertently by other actions - in the same way a car with a failed earthing strap can suffer from the accelerator cable becoming the return path for the starter motor.

 

[dragoon]

You said:



Sorry, that's nonsense.

The vast majority of marine engines do not have isolated returns. Volvo fitted some that were, most notably sail drive engines, yet other manufacturers fitted engine/saildrive combinations without isolated returns and they didn't all dissolve due to galvanic corrosion. There are millions of boats with non insulated returns and Volvo build a huge amount of engine/sterndrive combinations that were not isolated. Just because Volvo dream something up does not mean that it's true and it's incorrect to say that "Marine engine electrical accessories technically should all be of the insulated earth type"

You like the word nonsense don’t you?

You can tell me it’s nonsense all you like. I have a boat with an insulated earth setup from the maunfacturer. It’s not a sail drive setup. I also have a boat that has a conventional bonding from the manufacturer. I can see both types exist. I would be careful mixing components between so types, especially where it started as insulated earth.

 

[dragoon]

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

What nonsense.

You don’t believe there is a risk of accidental ignition on boats?

 

[PaulRainbow]

You don’t believe there is a risk of accidental ignition on boats?

I don't believe that diesel engines on a boat require an ignition protected starter motor.

 

[dragoon]

I don't believe that diesel engines on a boat require an ignition protected starter motor.

diesel and no lpg on board maybe. This would be a minority of boats.

 

[179580]

You said:



Sorry, that's nonsense.

The vast majority of marine engines do not have isolated returns. Volvo fitted some that were, most notably sail drive engines, yet other manufacturers fitted engine/saildrive combinations without isolated returns and they didn't all dissolve due to galvanic corrosion. There are millions of boats with non insulated returns and Volvo build a huge amount of engine/sterndrive combinations that were not isolated. Just because Volvo dream something up does not mean that it's true and it's incorrect to say that "Marine engine electrical accessories technically should all be of the insulated earth type"

Seem to remember in the dim past doing continuity checks twixt engine and sail drive. Think was VP introduced a insulating collar??

 

[PaulRainbow]

You like the word nonsense don’t you?

You can tell me it’s nonsense all you like. I have a boat with an insulated earth setup from the maunfacturer. It’s not a sail drive setup. I also have a boat that has a conventional bonding from the manufacturer. I can see both types exist. I would be careful mixing components between so types, especially where it started as insulated earth.

If something is nonsense, it's nonsense, so that's the appropriate word.

For the last time, you said originally:

Marine engine electrical accessories technically should all be of the insulated earth type and not have a negative feed via the case or chassis.

I stated that's nonsense, which it is. You have now changed what you're saying to " I can see both types exist", which is of course correct, but not what you originally stated.

If you were to fit parts from a non isolated engine to your isolated engine they simply won't work, because there there is no return path. You would have to fit a negative cable somewhere. This would likely be a bad idea, as the engine isn't going to be connected to an anode. I've never suggested doing such a thing.

 

[179580]

diesel and no lpg on board maybe. This would be a minority of boats.

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.

 

[PaulRainbow]

diesel and no lpg on board maybe. This would be a minority of boats.

Boats are not fitted with ignition protected equipment just because they have LPG onboard. If they are fitted with petrol engines, they are (or at least they should be).

 

[dragoon]

If something is nonsense, it's nonsense, so that's the appropriate word.

For the last time, you said originally:



I stated that's nonsense, which it is. You have now changed what you're saying to " I can see both types exist", which is of course correct, but not what you originally stated.

If you were to fit parts from a non isolated engine to your isolated engine they simply won't work, because there there is no return path. You would have to fit a negative cable somewhere. This would likely be a bad idea, as the engine isn't going to be connected to an anode. I've never suggested doing such a thing.

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.

 

[PaulRainbow]

Seem to remember in the dim past doing continuity checks twixt engine and sail drive. Think was VP introduced a insulating collar??

Yes, most of their saildrive units have an insulating "gasket" between the drive and the engine. But they did some without and they also insulated some shaft drive units too, anyones guess what their thinking was, but then is is Volvo.