Mercruiser alternator upgrade, can't find it!

(espritv8) · (espritv8) **Join Date: Dec 2009** 03-31-2010, 4:57 PM

Hi,

I want to upgrade my alternator. I've been looking on the internet all over but i only could find stock amperage alt's (65-70 amps). I would like something in the ballpark of 90-100 amps, and not too expensive like balmar or others. Db electrical doen't seem to carry what i need, but i'm not sure.

I have a 350 black scorpion engine in my 2008 supreme.

thanks

(polarbill) · (polarbill) **Join Date: Jun 2003** 03-31-2010, 7:21 PM

Quote:

Originally Posted by espritv8

Hi,

I want to upgrade my alternator. I've been looking on the internet all over but i only could find stock amperage alt's (65-70 amps). I would like something in the ballpark of 90-100 amps, and not too expensive like balmar or others. Db electrical doen't seem to carry what i need, but i'm not sure.

I have a 350 black scorpion engine in my 2008 supreme.

thanks

Does your current alternator have dual lower mounts? The Delco 7si is probably the stock alternator which is a 70amp unit. It actually puts out up to 90 amps in cooler temps. In real world applications it probably is closer to 70-80 amps. I know for Indmar they use a 2 inch spool lower mount. That style has a Delco OEM upgrade to the 11si which is a slightly larger alternator than the 7si but fits. I will check tomorrow with Delco and see if there is a dual foot 11si available. If not you may be out of luck.

(_vitty_) · (_vitty_) **Join Date: Jul 2009** 04-01-2010, 5:02 AM

Hey Brett,
I have a Mercruiser 8.1L Horizon motor. I was trying to look around for alternator upgrades as well, but am not quite sure what to look for. It currently has a 65A alternator on it, but I would like at least a 100amp. Could you help me out by chance?
Thanks!

(acurtis_ttu) · (acurtis_ttu) **Join Date: May 2004** 04-01-2010, 5:57 AM

snap a picture of it. someone can tell what to look for.

(polarbill) · (polarbill) **Join Date: Jun 2003** 04-01-2010, 7:53 AM

Is this what your alternator looks like with the dual lower foot? From what I can tell they have used this alternator since 1998 on all engine's 4.3L and above. This is the 70 amp delco 7si.

(polarbill) · (polarbill) **Join Date: Jun 2003** 04-01-2010, 8:01 AM

Well, I just got off the phone with delco and they don't make an 11si with the dual foot. Can someone with a Black Scorpion of newer Mercruiser confirm that the alternator is a dual foot?

(Showmethebutter)

I'd be interested to find this out too, I have a 4.3lx with a 65 amp alt and would ideally like 100a.

Does a larger alt use up more hp?

(espritv8) · (espritv8) **Join Date: Dec 2009** 04-02-2010, 6:07 PM

Yeap my alternator looks like this one. I'm not sure it's 100% identical with the dimentions, but it's a 70amp and it appears to have a dual foot..

(espritv8) · (espritv8) **Join Date: Dec 2009** 04-10-2010, 9:00 AM

So i guess i'm out of luck with this.

Do you think it could be upgraded by a specialist to get around 100 amps?

(espritv8) · (espritv8) **Join Date: Dec 2009** 05-30-2011, 3:29 PM

Found one. API marine had the same alternator rate at 100amps.

Should it be plug and play, or I need to upgrade other items on the boat?

I have a 150amp breaker and a 70 amp battery isolator.

Thanks

(jeff359) · (jeff359) **Join Date: Jun 2005** 05-30-2011, 5:16 PM

I took mine out and had an alternator shop, here locally, upgrade mine. No issues and plenty of juice

(espritv8) · (espritv8) **Join Date: Dec 2009** 05-30-2011, 6:46 PM

Did you re-installed it with no modifications? Maybe thicker wiring to the batteries?

(rockstarcustoms)

excessive amperage in florida, they built one for me for a mercruiser 180 amp, and I have been talking to him about a 300 amp for another boat, and its really reasonable

(wake_upppp) · (wake_upppp) **Join Date: Nov 2003** 05-30-2011, 9:27 PM

No wiring mods needed if you stay around 100 amps. Have a local alt shop do the upgrade to your existing alt.

(espritv8) · (espritv8) **Join Date: Dec 2009** 06-01-2011, 7:26 AM

Great. I called local shop, and they can do it.

Just wonder if they can keep the alt under marine specifications (ignition protection etc..)

(polarbill) · (polarbill) **Join Date: Jun 2003** 06-01-2011, 8:46 AM

Chris, no offense but there is no reliable way to get 180 and definetely no way to get 300 amps out of a small frame alternator.

(crowem87) · (crowem87) **Join Date: Nov 2005** 06-01-2011, 9:40 AM

Just wondering... what all are you guys running that requires so much amperage from the charging system?

(polarbill) · (polarbill) **Join Date: Jun 2003** 06-01-2011, 9:52 AM

Matt, I am not sure upgrading the alternator in a wakeboarding boat is even worth it the way most people use their boat. Grant is the only one that I have seen that makes sense. Mos tof these guys would be better off spending their money on more/better batteries and buying a good 2 bank charger.

(crowem87) · (crowem87) **Join Date: Nov 2005** 06-01-2011, 10:14 AM

Brett,

I agree, I guess my question was more of a polite way of asking WTF they need it for haha. I mean unless you have a serious system, lights....etc (which i know some of you guys do) it seems like it would not be that helpful. One could just run a 2nd or 3rd battery. Most boats I have run into at our shop will have one battery with the main power leads running to it, and the second will have all the accessory power such as PP, stereo, Lights.... It seems a std. alternator would be able to maintain 2 batteries at a full charge except extreme circumstances. I just found it interesting that so many people are interested!

(espritv8) · (espritv8) **Join Date: Dec 2009** 06-01-2011, 12:56 PM

Well, I have:
600W RMS for the tower
540 W RMS in the boat
600W RMS for the subs

I plan on adding tower lights, and i also have integrated ballasts pumps.
I was told this was too much for my alternator.

Anyway, got back from the shop, they can't do it. It's a delco 7si and apparently they don't make any parts to modify it. Did anybody got his 7si alt (standard on black scorpion) upgraded? Any references?

(polarbill) · (polarbill) **Join Date: Jun 2003** 06-01-2011, 1:09 PM

Do you have the ability to plug in at night? I would skip upgrading the alternator and go with a nicely sized stereo bank(for your amperage a couple deep cycle group 27s should fit the bill) and get a 2 bank charger. I believe west marine has a 20amp 2 bank prosport for about $150. This in conjunction with a good sized stereo bank would do you much better then upgrading your alternator 20 or 30 amps.

(espritv8) · (espritv8) **Join Date: Dec 2009** 06-01-2011, 1:17 PM

I already have 232 amp-hour battery bank (2 6v cart batteries) and a dual bank charger. Think that's enough?

Anyway, upgrading the alt seems impossible, can't find th right alternator or even replacement parts to upgrade it.

(polarbill) · (polarbill) **Join Date: Jun 2003** 06-01-2011, 1:40 PM

Your battery and charger setup sounds good. I just don't think it is worth it to upgrade the alternator.

(espritv8) · (espritv8) **Join Date: Dec 2009** 06-01-2011, 7:44 PM

OK.

If i want to add other batteries on my stereo bank, can I just plug them in parallel with the others? I already have an isolator for the starting battery.

(espritv8) · (espritv8) **Join Date: Dec 2009** 06-01-2011, 8:51 PM

And my battery charger is a Prosport 8.