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.

 

[BigEasy]

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?

There are a few companies that manufacture Hitachi style alternators & market them on EBay. I opted to rebuild my 55 amp Hitachi alternator. The diode-rectifier. & regulator module is available for approximately $60.00. If you have basic mechanical & soldering skills, there is no reason that you can’t do the repair yourself as long as the windings are OK,

 

[east coaster]

When I bought our 2002 310 it had the same battery configuration that you stated. I changed it to series/parallel trojan 105 fla batteries giving me 450 amps of which half are usable. I added a separate start battery that is charged by an ACR to the main bank. Got rid of the 35 amp alternator and found a 65 amp one that I configured for an Sterling external regulator. Also have 3 solar panels (dodger 130 watts and two on the bimini at 115 watts each) . They go to separate mppt controllers as does the alt output which goes directly to the battery bank. A 60 amp smart charger is there as well but seldom used as the solar panels keep the bank up even with the refrigerator running. The only time I have seen higher voltage going to the house bank is when when they are in a programmed equalization cycle which Trojan battery states should be just over 15 volts. Main bank may drop to 90 % state of charge overnight with fridge on, but solar brings it up quickly even on cloudy days here in Nova Scotia. After all the above my suggestion is have the alt rebuilt and while it's apart configure it for an external regulator. You can do this yourself to get familiar with the system and it's operations. There are plenty of you tube videos of this task as that is how I learned and am grateful for it. I have had no issues or problems with the above configuration and just have to check the water level in the batteries on a regular basis. Except for the equalization and adding water it should work as well for AGM batteries as well. Just my experience in dealing with a similar issue that you are confronted with.

 

[Project_Mayhem]

Searching for "55-amp OEM Hitachi alternator" revealed a TON of compatible units. I opted to rebuild because it's something that I always wanted to try and I didn't want to deal with any incompatibilities with mounting. There are quality alternator shops out there but they wont be cheap.