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Old 03-23-2020, 02:10 PM   #1
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What alternator on my new Mercruiser 6.2 L

I already know that most here have diesels with a smattering of gas engine owners. And of those gas engine owners, an infinitesimal number of folk have purchased the new Mercruiser engine.

I recently purchased the latest engine, just released not too long ago so note this isn't the same engine as in the past in small block Merc V8's people own. I want to add a regulator to turn my alternator into a "smart" alternator, this allows more amps to come from the alternator to the batteries.

The current alternator will have an internal regulator. Most alternators, not modified, only produce roughly half of the stated AMP's so my 70 AMP alternator will only put out roughly 35 - 40 AMPs. But the alternator will probably have to be modified. Now you will have a hard time believing this but it is factual. My motor guy phoned Merc to ask what brand of alternator was on the engine. Ready....ready? The don't know.

So if any of you have installed a new Mercruiser 6.2 L 350 hp and are engine savvy, do you know what alternator is being used?
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Old 03-23-2020, 02:15 PM   #2
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From what I can find, most of the newer Mercruisers use a 70 amp Delco style alternator. Can't find a definite answer on which Delco series it is, however. Older Mercruisers typically used Motorola or Mando alternators, but I don't think those came in anything bigger than 65 amp.

If you can grab a couple of pictures of what you've got, that might help with identifying it.
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Old 03-23-2020, 02:16 PM   #3
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Greetings,
Mr. 48. There is NO information on the alternator itself? No numbers, letters or tags? Anywhere?
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Old 03-23-2020, 02:28 PM   #4
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Quote:
Originally Posted by rsn48 View Post
I already know that most here have diesels with a smattering of gas engine owners. And of those gas engine owners, an infinitesimal number of folk have purchased the new Mercruiser engine.

I recently purchased the latest engine, just released not too long ago so note this isn't the same engine as in the past in small block Merc V8's people own. I want to add a regulator to turn my alternator into a "smart" alternator, this allows more amps to come from the alternator to the batteries.

The current alternator will have an internal regulator. Most alternators, not modified, only produce roughly half of the stated AMP's so my 70 AMP alternator will only put out roughly 35 - 40 AMPs. But the alternator will probably have to be modified. Now you will have a hard time believing this but it is factual. My motor guy phoned Merc to ask what brand of alternator was on the engine. Ready....ready? The don't know.

So if any of you have installed a new Mercruiser 6.2 L 350 hp and are engine savvy, do you know what alternator is being used?

Post a photo.. It is most likely an 11SI. We built a 100A model for a guy a couple of years ago and that alternator was a PITA to covert....
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Old 03-24-2020, 06:26 AM   #5
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A 70A alt with a 3 or 4 stage V regulator will not pump out 70A for long.

Install a SOC meter and see how down the house batts are after a normal night .

If there is room switch over to a large frame alt that is still ignition protected.

If it can be mounted as a second alt , for the house bank, its even better.
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Old 03-24-2020, 09:05 AM   #6
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I think what Fred is saying above is if you modify a small 70A alternator to work with an external regulator it will overheat, bake the windings and/or diodes and fail prematurely.

Although I do not know much about Delco alternators, I believe that there are other heavier duty alternators that you can buy, some with external regulator terminals that can be used with an external regulator. If you don't push them too hard and particularly if you use Balmar's alternator temperature probe which cuts output in half when too hot, they should last.

A simple solution is to call Balmar and order their high output alternator to fit your mounting. But it will be $500-700 ex regulator.

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Old 03-24-2020, 11:00 AM   #7
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If you want a standard alternator, 3 options, look for the plate on the existing alternator. Call the engine manufacturer of the engine.... they will no doubt give you more than one option. Interrogate google.... the results will no doubt give you options.
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Old 03-24-2020, 11:31 AM   #8
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Greetings,
Mr. OD. We don't know yet if there are any identifying marks or labels on the existing alternator. (post #3)
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Old 03-24-2020, 11:33 AM   #9
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Quote:
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Greetings,
Mr. OD. We don't know yet if there are any identifying marks or labels on the existing alternator. (post #3)
You still have the option of goggling or calling the manufacture or a dealership
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Old 03-24-2020, 08:58 PM   #10
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My boat is roughly an hours drive away. My refit guy sent me pics but there is no identifying marks on the plates that are visible. Instead there are maintenance instructions on the plate for the engine. The new Merc stern drive gas engines are no longer auto engines, they have contracted out a manufacture for the iron block V8 but the rest is built by Merc which is why I stipulated earlier that this is not the old Merc V8's. They could very well be Delco alternators which I know was used in the past, but it might be something else. We will be removing the alternator to check it out. We figure any identifying marks will be on the back which visually isn't accessible.
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Old 03-25-2020, 06:01 AM   #11
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I am not sure how many large output alts are ignition protected for a gas engine.

Diesel large frame alts (no protection) are cheap and easy to get 135A about $135.00, plus fan sheve and V regulator.


It might be simpler and cheaper in the long run to simply mount a second gasser alt to handle the overnight house loads.
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Old 03-25-2020, 07:09 PM   #12
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Mr. RSN48: I have one of those engines in my boat. I went to the boat this morning to look at the alternator, and found nothing at all. Nothing is marked with any brand names on any of the engine peripherals. See attached pics. It might be that your engine is newer - you may be able to compare my serial numbers to yours. I bought my boat new (custom build) in Jan. 2017 - so engine may have been made in 2016 or thereabouts and dropped into the boat during the February 2017 build. I wish I could provide more info, but hope this helps some.
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Old 03-25-2020, 07:40 PM   #13
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The belt routing diagram shown in the picture shows the alternator pulley (small one top center-right) under the flat cover.
MerCruiser website specs 70 amp/882 watts.
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Old 03-25-2020, 07:59 PM   #14
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It is a whole new world as much for boat engines as it is for car engines.
It is not trivial to retro-fit an aftermarket alternator to a serpentine belt engine.
Your alternator will be internally regulated and may be difficult to convert to external.
If you decide to change what you have I would talk to a shop that specializes in
modding boat engines like yours. You may be able to use an aftermarket set-up that
can accommodate the kind of alternator you are after.
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Old 03-25-2020, 08:01 PM   #15
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Get the engine serial number, call the manufacture and talk to them about the alternator. I will bet they dont know but, will give you at least 3 options.
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Old 03-26-2020, 04:03 PM   #16
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OldDan the problem is the alternator serial number is on the not visible side of what we can see. Taking the alternator off is the only way to identify it. I started this thread also in The Hull Truth and became the bad guy. I dared criticize Mercury. I guess there is some advantages to talking to old farts on this forum to get advise (I'm an old fart).

Mark P, I looked at the pics of the alternator my refit guy sent and it looks like the alternator is the top wheel of the pulley on the right by the black pipes in your picture.

Right now we are looking a plan B. When all of my refit planning began, I originally planned on a higher amp powered alternator (140 amp) on my old marinized chevy block V8 - 270 hp. When we discovered there were a multitude of problems with the engine and leg, I went into repower mode. First called Volvo, they didn't want to sell me their V6 Aluminum 240 hp as they were worried about engine burn out pushing my roughly 29 foot cruiser, this kind of backs up what David Pascoe has said about aluminum engines in boats.

Going to Merc began as a money saving plan, and I was originally looking at the new V6 4.5 L 250 hp engine. Then I asked about price difference to go to the V8 and was told it would be roughly $3,000. What I liked about the V8 as that I could go at cruising speed and the engine would be less stressed out thus hopefully lasting longer. Getting extra speed was a bonus. As many have said, there is no replacement for displacement.

When I talked to Mercury they didn't want me to change out the alternator and I was going to take this advice. But I am at the point I'm thinking screw it, apparently I still own the 140 amp alternator, I hadn't been credited with that money.

My refit guy called Jeff Cote about this issue of alternators and getting the proper voltage in with an external regulator. Jeff recommended a swap out of alternators. Jeff has no iron in the fire to make money off of me in this transaction.

I am going to link Jeff Cote's talk at the 2016 Vancouver Boat Show on external regulators. One interesting fact I learned is that lithiums are really hard on most alternators and can burn them out, this comes near the end of the video:

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Old 03-26-2020, 05:08 PM   #17
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Realize that all you have to do is find a replacement alternator with the same mounting system, the right pulley and offset. I will bet Delco, Leece Neville and of course the Chinese have lots of choices. Look for one with 150A output and external regulator terminals.

Call around. Tell the shops that you think you have a Delco 11SI or similar and want more beef and go from there.

This is a serpentine belt drive, right? which won't have any problem with 150A like a single 1/2" belt would.

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Old 03-27-2020, 06:40 AM   #18
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MerCruiser website specs 70 amp/882 watts.[/QUOTE]


Divide 882 watts by the charge voltage needed , say 14.4 and you will not get 70A .
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