Are all boat alternators created equal?

[JCUMV]

Guys,
Had a situation recently that I want to run by you. I have a 1987 26' Caribbean daycruiser, 454/Alpha configuration. Picked it up last summer and we've really enjoyed the boat so far. This past Christmas, we took it to Long Beach harbor and joined the boat parade. I bought an Inverter from West Marine, picked some LED xmas lights and did the boat up nice. In the cabin of my boat are two overhead 5" dome lights, and two more adjustment reading lights are up in the front of the cabin (these 2 are LED's).

So those 4 cabin lights, plus 2 courtesy cockpit lights, plus the LED xmas lights via the converter were all on for about 2 hours while we did the parade. Pulled the boat out of the water after the parade, and over to the wash rack. Went to re-start the boat, and the batteries were 90% dead. It barely turned over. Got a jump from another guy on the wash rack and proceeded to wash her up and flush the motor, etc.

There are two batteries in the boat, both blue top optimas. They're 4 years old. The alternator is likely OEM and original. Granted, I was only cruising at 5 mph for those couple hours and probably not generating much amperage, but shouldn't the alternator still keep up with that? I've order LED replacement lights for everything on the boat, so that will help. But still... I wouldn't think this should happen. Thoughts?

Thanks!

 

[Backlash]

Could be a combination of things.... Old alternator not charging sufficiently. Old Optima batteries not holding a charge. A short in the system. Or, all of the above.

I would start with the alternator and have it checked. Then the batteries. The old Optima's would last 8-10 years, but now I've heard they are lasting only 3-5 years.

Something you also want to check is how the batteries are all wired in and connected. You want to make sure you have at least one battery dedicated as a "Start" battery. Use the others for accessories and such. This way you can run your electronics and lights and stuff, without worry when it comes time to start the engine. Then, once started, the engine can recharge the accessory batteries.

 

[plaster dave]

I always try and get starters and alternators from autozone so I can swap out in Havasu if I have a failure.

 

[Rajobigguy]

No not all alternators are created equal.

http://www.dbelectrical.com/c-7743-mercruiser.aspx?pagenum=1

 

[wsuwrhr]

Could be a combination of things.... Old alternator not charging sufficiently. Old Optima batteries not holding a charge. A short in the system. Or, all of the above.

I would start with the alternator and have it checked. Then the batteries. The old Optima's would last 8-10 years, but now I've heard they are lasting only 3-5 years.

Something you also want to check is how the batteries are all wired in and connected. You want to make sure you have at least one battery dedicated as a "Start" battery. Use the others for accessories and such. This way you can run your electronics and lights and stuff, without worry when it comes time to start the engine. Then, once started, the engine can recharge the accessory batteries.

Exactly how it should be done if it isn't already. I love that others "get it"

I love this board.

Brian

 

[wsuwrhr]

What backlash said for sure.

Likely it is a combination of both. I assume since you are asking you don't have a voltmeter or amp gauge onboard. Both serve a separate purpose.

On batteries that mostly sit, I'd venture to say they are on their way out.

They should be fully charged and load tested. Remove the alternator and have it bench tested. Then decide what to do.

Brian

There are two batteries in the boat, both blue top optimas. They're 4 years old. The alternator is likely OEM and original. Granted, I was only cruising at 5 mph for those couple hours and probably not generating much amperage, but shouldn't the alternator still keep up with that? I've order LED replacement lights for everything on the boat, so that will help. But still... I wouldn't think this should happen. Thoughts?

Thanks!

 

[Taboma]

I always try and get starters and alternators from autozone so I can swap out in Havasu if I have a failure.

Do they carry CG approved Marine SAE J1171 starters and alternators at Autozone in Havasu ? I hope you're not sticking automotive versions under your hatch :yikes

 

[plaster dave]

Yes they do. It's a big part of their business.

 

[wsuwrhr]

Do they carry CG approved Marine SAE J1171 starters and alternators at Autozone in Havasu ? I hope you're not sticking automotive versions under your hatch :yikes

Expand on that please.

Enclosed to contain sparks?

I am new to this market and have been thinking about those things

 

[Taboma]

Essentially brushes (arc producing point of contact) are contained and sealed to prevent explosion of fumes in confined bilge areas.

Here's a quick read

http://www.jamestowndistributors.com/userportal/pdfs/howtos/Tech_Marine_Alternator_tips.pdf

I doubt most V-drivers or jet boats with open engine compartments sweat it.

 

[OLDRAAT]

Concur, get the CG approved alt as he mentioned. Saw a boat have a flash explosion due to an open alternator at a marina awhile back. Old school cig cafe racer, it blew the hatch up and knocked a couple of girls off. :yikes

When I replaced mine a few years ago, I replaced it with a 140 amp unit which was only a few bucks more than the standard one.

OR

 

[RiverDave]

There are lots of shops around that can rewind your alternator and make it put out a ton more amperage.

RD

 

[wsuwrhr]

Yep and now I have one in an enclosed compartment. So now I am.

Essentially brushes (arc producing point of contact) are contained and sealed to prevent explosion of fumes in confined bilge areas.

Here's a quick read

http://www.jamestowndistributors.com/userportal/pdfs/howtos/Tech_Marine_Alternator_tips.pdf

I doubt most V-drivers or jet boats with open engine compartments sweat it.

 

[rivermobster]

Guys,
Had a situation recently that I want to run by you. I have a 1987 26' Caribbean daycruiser, 454/Alpha configuration. Picked it up last summer and we've really enjoyed the boat so far. This past Christmas, we took it to Long Beach harbor and joined the boat parade. I bought an Inverter from West Marine, picked some LED xmas lights and did the boat up nice. In the cabin of my boat are two overhead 5" dome lights, and two more adjustment reading lights are up in the front of the cabin (these 2 are LED's).

So those 4 cabin lights, plus 2 courtesy cockpit lights, plus the LED xmas lights via the converter were all on for about 2 hours while we did the parade. Pulled the boat out of the water after the parade, and over to the wash rack. Went to re-start the boat, and the batteries were 90% dead. It barely turned over. Got a jump from another guy on the wash rack and proceeded to wash her up and flush the motor, etc.

There are two batteries in the boat, both blue top optimas. They're 4 years old. The alternator is likely OEM and original. Granted, I was only cruising at 5 mph for those couple hours and probably not generating much amperage, but shouldn't the alternator still keep up with that? I've order LED replacement lights for everything on the boat, so that will help. But still... I wouldn't think this should happen. Thoughts?

Thanks!

Alternators are NOT created equal, especially marine alternators!!! You do NOT want any sparks in a sealed engine compartment. DO NOT use a car alternator!!!

With that outa the way, here is what you need to do...

First, have both batteries charged and tested. You Cannot properly test an alternator with a bad battery. You will be chasing your tail for days.

Next, make sure all your battery cables are good, clean and tight, corrosion is NOT your friend.

You should have 12.7v at the battery with them fully charged. With the engine running at idle, you should see 14.2 at the battery. Yes? So far so good. No? alt is now a suspect.

Next, (even if your voltage checks are good), find someone with a clamp style amp gauge, to find out if the alt. can keep up. Put it around one of the cables (at the battery, or at the switch for dual batteries), to verify that you are charging. Now, start turning EVERY accessory on full. Blowers, radios, lights, any possible thing you can use.

Still charging???

Most likely not. Increase the RPM till you see it charge. If it does charge with the increased RPM, you have an alternator that just can't keep up. You'll need to either get a higher output alternator, or while watching the amp gauge, determine just how much stuff you can actually turn on, without exceeding what the alternator can do (at idle).

High output alternators are Expensive. High output Marine alternators are VERY expensive.

Make sense? PM or call me if not. http://jmsservicecenter.com/contact/

Good luck! :thumbup:

 

[HST4ME]

Older mandos and some prestolites do not excite enough to charge at low rpm (under 800), particularly dead idle speeds. it's easy to see on the volt gauge if you blip the throttle a little bit. Sometimes the pulley can be swapped out to a smaller diameter to circumvent this. I use Arco and Merc starter/alternators and that is it. :finger to the rest of the garbage out there.

 

[JCUMV]

Wow, great responses here guys. Thanks. Let me post a few comments...

Something you also want to check is how the batteries are all wired in and connected. You want to make sure you have at least one battery dedicated as a "Start" battery. Use the others for accessories and such. This way you can run your electronics and lights and stuff, without worry when it comes time to start the engine. Then, once started, the engine can recharge the accessory batteries.

Boat is definitely wired for this. And like a moron, I probably left it on BOTH during the drive. Still, I would've thought the alternator would have kept up with the demand. Some of these daycruisers came with refers and I assumed these switches were for if you planned to leave the refer on all night, you'd want to put it over to 1 or 2. But for 2 hours of cruising in the harbor with some lights on, it didn't occur to me to worry to about.

Alternators are NOT created equal, especially marine alternators!!! You do NOT want any sparks in a sealed engine compartment. DO NOT use a car alternator!!!

With that outa the way, here is what you need to do...

First, have both batteries charged and tested. You Cannot properly test an alternator with a bad battery. You will be chasing your tail for days.

Next, make sure all your battery cables are good, clean and tight, corrosion is NOT your friend.

You should have 12.7v at the battery with them fully charged. With the engine running at idle, you should see 14.2 at the battery. Yes? So far so good. No? alt is now a suspect.

Next, (even if your voltage checks are good), find someone with a clamp style amp gauge, to find out if the alt. can keep up. Put it around one of the cables (at the battery, or at the switch for dual batteries), to verify that you are charging. Now, start turning EVERY accessory on full. Blowers, radios, lights, any possible thing you can use.

Still charging???

Most likely not. Increase the RPM till you see it charge. If it does charge with the increased RPM, you have an alternator that just can't keep up. You'll need to either get a higher output alternator, or while watching the amp gauge, determine just how much stuff you can actually turn on, without exceeding what the alternator can do (at idle).

High output alternators are Expensive. High output Marine alternators are VERY expensive.

Make sense? PM or call me if not. http://jmsservicecenter.com/contact/

Good luck! :thumbup:

Great write-up. I bolded a couple sentences because I think they apply here. A month after the Xmas Parade, I took the boat to Newport harbor for another family cruise. There was just enough juice in the batteries to get her started on the ramp. As I cruised thru the harbor, the Volts meter read between 10-12. I didn't dare dock at the Fun Zone and turn the boat off! Instead, we went out to the open ocean and cruised up to Newport pier about 30 mph. The 20 minute drive out to the pier and back to the harbor had the Volt meter now reading between 12-14. We pulled into fun zone, shut it down, grabbed an ice cream, and came back. The boat cranked over much faster, but still not what I'd call normal. That revelation lead to this thread. I wasn't sure if this sounded like a battery problem or an alternator problem.

 

[77charger]

Sounds like a charging issue to me.I have mine wired so that stereo is on a separate dedicated battery but can still get charged from the alternator.I can put an inverter on this same battery too.My other battery is for the engine and boats lights which aint much power.

Oh the stock mercruiser alt is about 50-55 amps not much considering anything else besides a basic stereo and nav lights.

 

[rivermobster]

Wow, great responses here guys. Thanks. Let me post a few comments...



Boat is definitely wired for this. And like a moron, I probably left it on BOTH during the drive. Still, I would've thought the alternator would have kept up with the demand. Some of these daycruisers came with refers and I assumed these switches were for if you planned to leave the refer on all night, you'd want to put it over to 1 or 2. But for 2 hours of cruising in the harbor with some lights on, it didn't occur to me to worry to about.



Great write-up. I bolded a couple sentences because I think they apply here. A month after the Xmas Parade, I took the boat to Newport harbor for another family cruise. There was just enough juice in the batteries to get her started on the ramp. As I cruised thru the harbor, the Volts meter read between 10-12. I didn't dare dock at the Fun Zone and turn the boat off! Instead, we went out to the open ocean and cruised up to Newport pier about 30 mph. The 20 minute drive out to the pier and back to the harbor had the Volt meter now reading between 12-14. We pulled into fun zone, shut it down, grabbed an ice cream, and came back. The boat cranked over much faster, but still not what I'd call normal. That revelation lead to this thread. I wasn't sure if this sounded like a battery problem or an alternator problem.

A bit of both...

Optima's do not charge like a normal battery will. They will take 24-48 hours on a Slow charge to be fully charged up. What you did was put a "surface charge" on em. One or two engine cranking cycles, and they will be dead again.

The other thing is...

Converters suck a SHIT TON of juice!!!!!

When my kids were little, one HUGE 12v battery would last a little more than an hour with a playstation and 12" TV hooked up to it. Those things eat batteries like candy. You will kill an alternator trying to run one with it. A small generator would be a much better idea.

 

[JCUMV]

^ Well I can see how a Playstation and 12" TV would reek havoc on a battery, especially if you're cruising 5 mph. But 4 LED twinkle light strings, and some courtesy lights, I'd think that shouldn't put a dent in the battery even at 5 mph. I guess I'm wrong. If you're telling me that upgrading my alternator likely won't keep up with the demand, then I guess I'll just have to shine the xmas parade. I can't justify buying a generator for one event a year! Ha.

 

[wsuwrhr]

I ran my jetboat all day with NO alternator and dual batteries and never had a problem.

Me thinks you will be fine once you get it ironed out. New batts, alternator or a combo, do you have a charger? Are you local?

Brian

^ Well I can see how a Playstation and 12" TV would reek havoc on a battery, especially if you're cruising 5 mph. But 4 LED twinkle light strings, and some courtesy lights, I'd think that shouldn't put a dent in the battery even at 5 mph. I guess I'm wrong. If you're telling me that upgrading my alternator likely won't keep up with the demand, then I guess I'll just have to shine the xmas parade. I can't justify buying a generator for one event a year! Ha.

 

[Ziggy]

Think back to late last year in the channal and the boat whose engine hatch was blown off at start up late one night.
There's the answer to why it should always be marine grade.

 

[JCUMV]

I ran my jetboat all day with NO alternator and dual batteries and never had a problem.

Me thinks you will be fine once you get it ironed out. New batts, alternator or a combo, do you have a charger? Are you local?

Brian

Since the batts are 4 years old, I guess it makes sense to replace them. I was going to look at an alternator too, but after reading what rivermobster said I'm not sure if it's going to help. I don't have a charger. I'm in So Cal. Ladera Ranch.

 

[wsuwrhr]

Since the batts are 4 years old, I guess it makes sense to replace them. I was going to look at an alternator too, but after reading what rivermobster said I'm not sure if it's going to help. I don't have a charger. I'm in So Cal. Ladera Ranch.

I don't think it is more than batteries, and buy a tender when you buy them. 4 years in something that sits is a good run IMHO.

I will offer to charge them for you, but you are a ways from Upland, but if you come this way I would be happy to charge/load test them for you.

If the alternator is charging, you should be fine with dual batteries. If you are able to work on your own stuff, have the alternator benched at Auto Zone when you replace the batteries.

Brian

 

[Rsqfxr]

Was just looking into an upgraded alternator for my 496, the stock is 70 amps, my rebuilder says it's physically too small to upgrade, unsure if thats my guy or across the board I did find some higher output units on amazon so i may give that a shot

 

[ka0tyk]

i went to the long beach high performance swapmeet and theres a dude there that sells nothing but alternators. talked to him and i ended up scoring a 3 wire powdercoated 160 amp marine sealed alternator that was fairly inexpensive. quite the upgrade from the original 7 amp motorola that i had on there.