Mainship 390 (Yanmar 6LP-STE) alternator replacement

[mncruiser]

Howdy folks,

I'm researching replacing my stock alternator on my 2001 Mainship 390 with a single Yanmar 6LP-STE. Everything is working fine, but it seems about time to replace it based on age. I believe I have the stock Denso 80 amp alternator, running on a two groove pulley.

My mechanic suggested skipping a stock alternator, and suggested something like a Balmar with some upgraded charging features. We have a pretty simple setup:

-Starting bank - Two Group 31 AGM (105ah each)
-House bank - Two Group 31 AGM (105ah each) and one 4D AGM (170ah)
-590ah total

At this current stage of cruising, we are seasonal boaters with young kids up here on the Great Lakes, we aren't often away from the dock for more than about 2-3 nights at a time, with a few longer trips each season. I have a generator I can use to run the battery charger while away form the dock as well, but we try and limit use of that.

I think I want to upgrade the charging capacity to 100 or 120 amp, and it looks like I can get Balmar's "max charge" kit with an external regulator and temperature sensors as an upgrade as well. My questions and a few more details:

1. Should I consider other brands other than Balmar? They seem to have the exact kit I would need with pulleys and all that would keep it fairly simple.
2. Do I need their external regulator with temp sensors, or should I do something else? See next item for "something else" ideas.
3. I have a desire to add a small amount of solar to help with DC refrigeration loads (kids open the doors a lot) and have not fully researched this, but maybe there is something else I should be thinking about for future solar installation where I'd combine alternator/solar charging loads somehow?

The future solar stuff will probably not happen this season, need to learn more.

Thanks for any opinions and ideas you may have!

MNCruiser

 

[DavidM]

1. Balmar is a top brand, but expensive. There are other externally regulated alternators, but don’t know about quality.
2.Definitely go with external regulator and temp sensor.
3. Solar can be added at anytime. Wire the controller’s output directly (through an appropriately sized fuse) to the house battery terminals.

You need to review the isolation of your house and starting battery.

A 6LP is a little small for that boat, but if you keep your speed below 8 kts, you should be fine.

David

 

[READY]

I just upgraded to a Balmar XT 170 amp. Dual pulley. External Balmar smart regulator. Very easy upgrade and excellent documentation. If you go this route you will have many options for the future. There may be lower cost vendors and I am usually looking to save but in this case I think it is worth it. I don't expect to need to replace this for a decade or more so minimal savings amortization over the period. Balmar even has the std. Yanmar connector built into the harness. I installed on a Ford Lehman but still fairly simple. The alt temp sensor will protect the alternator and is very important. Takes 5 minutes to install. Battery temp sensor is similar and adds safety.

If it loads up your engine too much you can easily program it for reduced outputs.

Great addition to your boat.

 

[mncruiser]

1. Balmar is a top brand, but expensive. There are other externally regulated alternators, but don’t know about quality.
2.Definitely go with external regulator and temp sensor.
3. Solar can be added at anytime. Wire the controller’s output directly (through an appropriately sized fuse) to the house battery terminals.

You need to review the isolation of your house and starting battery.

A 6LP is a little small for that boat, but if you keep your speed below 8 kts, you should be fine.

David

Thanks for the reply.

For our use, the 6LP works great in the boat. We usually run about 8.2-8.5 kts, with our "high cruise" being about 9.3 kts, but that is if we are trying to make some tracks. The boat *will* go about 11.3kts max, but it makes the most enormous wake you've ever seen, and is rarely if ever our speed.

Coming from a smaller cruiser, I used to run 30kts. This was an adjustment, but a good one. If I ran at 7kts I would not have to go to the fuel dock all summer!

 

[mncruiser]

I just upgraded to a Balmar XT 170 amp. Dual pulley. External Balmar smart regulator. Very easy upgrade and excellent documentation. If you go this route you will have many options for the future. There may be lower cost vendors and I am usually looking to save but in this case I think it is worth it. I don't expect to need to replace this for a decade or more so minimal savings amortization over the period. Balmar even has the std. Yanmar connector built into the harness. I installed on a Ford Lehman but still fairly simple. The alt temp sensor will protect the alternator and is very important. Takes 5 minutes to install. Battery temp sensor is similar and adds safety.

If it loads up your engine too much you can easily program it for reduced outputs.

Great addition to your boat.

Thanks for the reply. Kind of my thought as well, the Balmar setup seems an easy swap and a reliable system. I'm ok spending extra $ here.

 

[DavidM]

Be careful at 9+ kts. At that speed you are beginning to “climb over the hump” which puts extra stress on the engine and significantly increases fuel consumption.

With that engine you really have a displacement trawler.

I had a MS 34T (a similar boat) with the Yanmar 370 hp engine. It was just just over the hump at 12 kts and did 14-15 kts at wot.

David

 

[Cartouche]

Make sure it is compatible with your tach's as the tach's on the Mainship run off the alternator, found that out when my alternator quit

 

[O C Diver]

While I don't have a problem with Balmar, they don't make alternators, they buy them from other manufacturers. Their high capacity units are made by Leece Neville / Prestolite. Though there is something to be said for a complete kit as opposed to sourcing all the parts.

Understand that increasing amperage may require a heavier alternator output cable.

Ted

 

[mncruiser]

Be careful at 9+ kts. At that speed you are beginning to “climb over the hump” which puts extra stress on the engine and significantly increases fuel consumption.

With that engine you really have a displacement trawler.

I had a MS 34T (a similar boat) with the Yanmar 370 hp engine. It was just just over the hump at 12 kts and did 14-15 kts at wot.

David

Agreed, our normal speed is around 8. Works great for us.

 

[mncruiser]

While I don't have a problem with Balmar, they don't make alternators, they buy them from other manufacturers. Their high capacity units are made by Leece Neville / Prestolite. Though there is something to be said for a complete kit as opposed to sourcing all the parts.

Understand that increasing amperage may require a heavier alternator output cable.

Ted

Great point Ted, I'll be taking a look at all the wiring before I dig into it. Thanks!

 

[Shrew]

-House bank - Two Group 31 AGM (105ah each) and one 4D AGM (170ah)
-590ah total

How are these wired? Are they two isolated banks?

 

[Bacchus]

Make sure it is compatible with your tach's as the tach's on the Mainship run off the alternator, found that out when my alternator quit

The tach on our MS 34HT w single Yan 6LY runs off a separate sending unit located on stbd side aft of eng as it senses off the flywheel. I've had poor connection at terminals and a cleaning. & spot of grease solved my problem.
There is an adjustment ( spacing from flywheel) but be careful and know the details before making any adjustments.