Catalina 320: Battery Voltage gauge showed the needle going past 16 volts

[madmax]

While the engine was running, I noticed that the battery-voltage gauge on the pod (measured in volts) showed the needle going past 16 volts. Does that mean I have a bad voltage regulator inside the alternator? Does that mean I'll have to replace the whole alternator? What are my options?

The engine is a Yanmar 3GM30F.

 

[JoeWhite]

Those are not accurate. Use digital voltmeter to measure the alternator output. It should be about 14.4 volts with engine running

 

[Project_Mayhem]

Do you have solar or another charge source on while measuring voltage? As @JoeWhite mentioned, use a secondary instrument to measure voltage

 

[madmax]

No solar or other charge source.

If the voltage regulator is the culprit, should I replace the entire alternator, or should I take it to an alternator shop to have it rebuilt?

 

[Project_Mayhem]

There are various levels of rebuilds and not every shop will replace everything that they should. I'm guessing the price will be about the same but shop around. If this is the case, replacing would be the better option.

The PO of my boat accidentally reversed polarity of the battery terminals when he showed me the boat. It fried a few diodes in the alternator. It was very easy to repair. There's only three or so electrical modules in there. Cost was $20-30 to repair. If measuring with a multimeter reveals higher than normal voltage, have your alternator tested by a specialty shop. Autozone and others won't have the means to test these types of alternators. There may be shims to align the alternator. Be careful not to lose them and take note of their quantity/position.

 

[dlochner]

No solar or other charge source.

If the voltage regulator is the culprit, should I replace the entire alternator, or should I take it to an alternator shop to have it rebuilt?

Yanmar uses Hitachi alternators, they are not noted to be the best alternators for charging batteries. See for example this article:

Automotive Alternators vs. Deep Cycle Batteries - Marine How To

A Deep Cycle Battery Assassin The alternator pictured here helped to destroy a very expensive bank of TPPL AGM batteries in under two years. These batteries need an absorption voltage of 14.7V. The highest voltage I recorded on this vessel was 13.58V at the battery terminals. At this

marinehowto.com

Note, there are several other articles on alternators on the MarineHowtTo.com website.

Alternators are an important part of the boat's electrical system and should be matched to the battery and the type of sailing being done. An automotive style alternator, like the Hitachi, is fine for FLA batteries on boats that are mostly day sailed and connected to shore power. On the other hand they are a poor match for AGM and LFP batteries on boats left on a mooring or cruised extensively. Let us know what type of sailing you do and we can give you a more well informed answer.

 

[madmax]

Yanmar uses Hitachi alternators, they are not noted to be the best alternators for charging batteries. See for example this article:

Automotive Alternators vs. Deep Cycle Batteries - Marine How To

A Deep Cycle Battery Assassin The alternator pictured here helped to destroy a very expensive bank of TPPL AGM batteries in under two years. These batteries need an absorption voltage of 14.7V. The highest voltage I recorded on this vessel was 13.58V at the battery terminals. At this

marinehowto.com

Note, there are several other articles on alternators on the MarineHowtTo.com website.

Alternators are an important part of the boat's electrical system and should be matched to the battery and the type of sailing being done. An automotive style alternator, like the Hitachi, is fine for FLA batteries on boats that are mostly day sailed and connected to shore power. On the other hand they are a poor match for AGM and LFP batteries on boats left on a mooring or cruised extensively. Let us know what type of sailing you do and we can give you a more well informed answer.

My 1999 Catalina 320 has two 4D 12V flooded lead-acid batteries (for the house and engine starting systems). The battery charger is Victron Energy Blue Smart IP22 (about two or three years old). Most of time, the boat is connected to shore power. I use this boat for day sailing and once in a while visiting & staying at Catalina Island. While staying on the island, the boat is not connected to shore power; I'll have to rely on the house battery for one or maybe two nights. The island is about 25 NM from Long Beach, CA. I plan to get solar panels sometime in the future.

 

[dlochner]

I don't know what Catalina had against its customers' backs, 4Ds are effing heavy, 2 golf cart batteries provide about the same power in 2 manageable sizes. Oh well..

If you have to replace the alternator, then a larger internally regulate automotive style would work for you. Hitachi used to make an 80a alternator which would be a better size. Unfortunately I can't suggest an alternative. If you are considering adding LFP batteries in the future, then an externally regulated alternator would be a good choice. But first, see what's up with your alternator and whether it can be economically repaired.

 

[madmax]

Yeah, I agree with you. Those two 4D batteries are heavy. I've been thinking about getting four six-volt golf cart batteries, AGM (why you said two?) after the 4D batteries go bad.

 

[madmax]

I am trying to find a new 55-amp OEM Hitachi alternator. All I can find online are rebuilt alternators. The part number is 129772-77200.

Do you guys have any recommendations for the best rebuilt alternator? It’s my understanding that rebuilt alternators don’t last as long as new ones.

Also, where can I find a new OEM Hitachi alternator online?

 

[dlochner]

Yeah, I agree with you. Those two 4D batteries are heavy. I've been thinking about getting four six-volt golf cart batteries, AGM (why you said two?) after the 4D batteries go bad.

2 GC batteries per 4d. Also a 4D battery is not needed to start the diesel, a cheap group 24 battery will start it, however, if you use the start battery as reserve battery then 2 GC batteries work better.

Also, where can I find a new OEM Hitachi alternator online?

On a dusty back shelf of some supplier. Hitachi no longer makes the alternator.