Diesel start battery 3000scr

[darren uk]

Hi, I've a 3000scr with two mercruiser 4.2L 220ac diesel engines. The original batteries have been substituted for a couple of 220Ah dual purpose batteries of which one is now dead. Between them they run both the engine start and house supplies. I'd like to put back two dedicated engine start batteries as possibly was the original case, one for each engine and keep the house batteries separate and moved to the bow for better weight distribution. Looking at the manual for the engines it suggests using a 180Ah 750cca battery. Looking this capacity battery up, it shows the footprint to be huge, far bigger than what I think the currently redundant original battery tray is. This does seem like a meaty battery for each engine. If there's an owner out there with the same engines, what batteries have you got fitted. Any opinions will also be greatly received. Thanks.

[mmwjr]

Not sure the diesels were a factory option so you most likely looking at custom installation. If the engine manual list that battery I would look at option to install it or separate equivalent capacity batteries.

[darren uk]

Hi. Thanks. Do you mean buy two at half capacity and combine together on the switch if required. This way they would have a smaller footprint

[mmwjr]

Originally Posted by darren uk

Hi. Thanks. Do you mean buy two at half capacity and combine together on the switch if required. This way they would have a smaller footprint

Sort of. I meant two smaller hard wired in parallel to combine. Note there are some inefficiency in this so each should be slightly large than half the requirement from the manual.

[jparsons121]

As the OP mentioned, the factory didn’t provide for a true house bank. The engine batteries serve the house as well, so larger Ah batteries should have been installed.

I have done some rewriting on my gas 3000 and added a third bank of deep cycle batteries for handling the house loads. Each engine has a dedicated starting battery, which has the CCA rating and a decent Ah rate, but now that they only need to crank, the CCA or MCA rating is what mattered to me. High Ah needs size, so the starting batteries are now only Group 27 std sizes. A parallel switch is in-line so if I need to, I can join the house bank to the starting batteries if needed.

[shrew]

Originally Posted by mmwjr

Not sure the diesels were a factory option

There was a factory option, it was just incredibly rare to see them in the US due to cost. More popular for exports to Europe where gasoline is 5x the cost as compared to the US.

These were also very popular options for repower in Europe. Many people in Europe purchase US boats, ship them over and repower with diesel.

Recommended Battery Capacity Rating for the D4.2L//220:

750 cca
950 mca, or 180Ah

https://www.maritimepropulsion.com/files/pdf/1001256

[mmwjr]

Originally Posted by shrew

There was a factory option, it was just incredibly rare to see them in the US due to cost. More popular for exports to Europe where gasoline is 5x the cost as compared to the US.

These were also very popular options for repower in Europe. Many people in Europe purchase US boats, ship them over and repower with diesel.

Recommended Battery Capacity Rating for the D4.2L//220:

750 cca
950 mca, or 180Ah

https://www.maritimepropulsion.com/files/pdf/1001256

Yup understand the desire for diesel overseas and that it’s common for them to repower US boats that way just know it was a factory option.

[darren uk]

Originally Posted by jparsons121

As the OP mentioned, the factory didn’t provide for a true house bank. The engine batteries serve the house as well, so larger Ah batteries should have been installed.

I have done some rewriting on my gas 3000 and added a third bank of deep cycle batteries for handling the house loads. Each engine has a dedicated starting battery, which has the CCA rating and a decent Ah rate, but now that they only need to crank, the CCA or MCA rating is what mattered to me. High Ah needs size, so the starting batteries are now only Group 27 std sizes. A parallel switch is in-line so if I need to, I can join the house bank to the starting batteries if needed.

Hi Jparsons121. Thanks for your rely which all makes sense and is a feasible option for me. With the petrol engines their footprint appears to be far smaller than the diesels leaving quiet a bit more space between the engine and mid cabin bulkhead unlike the tight space left with my diesels. Did you fit your house batteries in this space somewhere?. I'm considering putting my house battery/s under the bow berth. Do you charge each of your engine batteries from each dedicated engine alternator and or dedicated charger when hooked up. How do you charge your house batteries. Thanks

[darren uk]

Thanks for confirming the data I had and your other info. I'm not sure if mine was re-powered but I know the diesels are quiet rare, even in the UK. Someone suggested to me only around 10% of the 3000's are diesel.

[darren uk]

Originally Posted by shrew

There was a factory option, it was just incredibly rare to see them in the US due to cost. More popular for exports to Europe where gasoline is 5x the cost as compared to the US.

These were also very popular options for repower in Europe. Many people in Europe purchase US boats, ship them over and repower with diesel.

Recommended Battery Capacity Rating for the D4.2L//220:

750 cca
950 mca, or 180Ah

https://www.maritimepropulsion.com/files/pdf/1001256

Shrew. Thanks for confirming the data I had and your other info. I'm not sure if mine was re-powered but I know the diesels are quiet rare, even in the UK. Someone suggested to me only around 10% of the 3000's are diesel.

[shrew]

Originally Posted by darren uk

Shrew. Thanks for confirming the data I had and your other info. I'm not sure if mine was re-powered but I know the diesels are quiet rare, even in the UK. Someone suggested to me only around 10% of the 3000's are diesel.

Maybe 10% in the UK. I wouldn't know. I'd guess far less than that in the US. Though neither that, nor whether they are OEM or repower, actually matters.

The D4.2L/220 is what you have now, and those (See link) are the specs for those motors.

[jparsons121]

Originally Posted by darren uk

Hi Jparsons121. Thanks for your rely which all makes sense and is a feasible option for me. With the petrol engines their footprint appears to be far smaller than the diesels leaving quiet a bit more space between the engine and mid cabin bulkhead unlike the tight space left with my diesels. Did you fit your house batteries in this space somewhere?. I'm considering putting my house battery/s under the bow berth. Do you charge each of your engine batteries from each dedicated engine alternator and or dedicated charger when hooked up. How do you charge your house batteries. Thanks

I don’t have a genny to work around, so I placed the house bank portside forward in the ER and left the staring batteries in place on the starboard side. The extra weight of the house bank helped to offset the water heater weight. It’s positioned stbd just aft of the starting batteries.
I was tempted to use one large (like an 8D) centerline, but I didn’t like how much rework I’d have to do make a suitable mount and didn’t like the battery potentially having bilge water so close to it.

You can place them forward, just keep in mind that all the main wiring back to the switches, charger, etc. will need to be upsized to handle the voltage drop/resistance when running 50 additional ft round trip.

For charging, I have a Promariner 3 Bank charger when on shore power.
When underway, each engine battery is charging via its own alternator.
House bank is charged as well thru an Bluesea ACR also fed by the port alternator. This allows just one engine to charge both when underway or on the hook.
It was a lot of re-connecting of the factory setup to use the 1-2-both-off switches the way I wanted it to be configured. I also added a on-off to allow the house to serve as a emergency start as well.