Engine wiring 1979 228 Mercruiser ??

[moonrakercat]

Hi Guys - hoping someone can help me - I'd like to upgrade to a higher amperage alternator - but want to check out the engine wiring for my merc beforehand - and am looking for the schematics - I've looked in the stickies with no success - maybe I'm missing something - and my seloc manual gives little help.

Anyone give me advice on where to find the wiring schematics ??

Please & thanks in advance - Matt.

 

[Bt Doctur]

the standard alt works just fine and as far as the wiring what amp output are you working with. #6 wire is more than adequate from the output post to the starters post.

 

[moonrakercat]

the standard alt works just fine and as far as the wiring what amp output are you working with. #6 wire is more than adequate from the output post to the starters post.

:facepalm:

Yes - I know the alternator works fine - stupid I'm not - however - I'd like to be able for my alternator to run some new electronics I've installed - so the 50 amp or so output will be insufficient or running at it's limit - and I'm not comfortable with that. I'm not going into specifics- I've asked a simple question - just hoping for some help.

So if you can help me out with a detailed ele schematic - much appreciated.

 

[Bt Doctur]

even a full boat of todays electronics the power needed will be covered by a standard alt. If worried about a weak starting batter, install 1 or 2 dedicated house batteries for the electronics.
click to enlarge

 

[Scott Danforth]

you have an amp meter. you are limited by that, so no reason to go bigger with the alternator.

or re-wire your boat/motor to go bigger alternator.

 

[moonrakercat]

even a full boat of todays electronics the power needed will be covered by a standard alt. If worried about a weak starting batter, install 1 or 2 dedicated house batteries for the electronics.
click to enlarge

Actually the above might help me - I'll check to see if the wires match mine ! Thanks

 

[moonrakercat]

Boat is going to have a 1000 w inverter installed to run 120 electronics also.

 

[moonrakercat]

you have an amp meter. you are limited by that, so no reason to go bigger with the alternator.

or re-wire your boat/motor to go bigger alternator.

My boat does not have an ammeter - that does not limit current fyi.

 

[Bt Doctur]

A ran a 1200 watt one and at max output 1200 watts of whatever was plugged in , the input current was 100 amps.
So you would be looking at 2 large capacity house banks and atleast #1 or #2 wire from the batteries to the inverter

 

[moonrakercat]

A ran a 1200 watt one and at max output 1200 watts of whatever was plugged in , the input current was 100 amps.
So you would be looking at 2 large capacity house banks and atleast #1 or #2 wire from the batteries to the inverter

I expect to draw maybe 500W from my inverter for short times - but when I do I would still like my 3 house batteries to charge as well as have enough to run the motor - and any lighting if I'm running in the evening - not to mention a few other items. So ideally a 80-90a unit would keep me fine. I could probably run with my existing alternator - but don't want to chance it if I really don't have to. I know I'm going to have to run a few extra wires for the extra current - but I want to double check the schematic for the charging system before I jump in too deep.

The schematic you have sent above is much appreciated - it is similar to my merc - but not quite it - the schematic you sent says pre BIA on it - not sure what that means ?? My merc has a Motorola alternator system - I found a Clymer manual that is very close - do you mind if I ask where you found that schematic above ??

I really appreciate your help on this - usually I can find things on the web but I'm coming up empty.

 

[Bt Doctur]

Mercruiser Manual 3

 

[achris]

If you have a voltmeter, then this should be what you're looking for. (BIA is Boating Industry Assoc. In the late 70's Merc adopted BIA wiring colour codes)...

With an 80A or 90A upgrade (standard alternator is either 37 or 55Amp, depending on which alternator), I would also increase the size of all the wires running from the alternator output to the battery! By all means, a higher output alternator will be an advantage if you plan on using your high current consumers while under way. But if you are hoping to use the higher output alternator to recharge the batteries very quickly, that's a very bad idea. It doesn't help with how much you drain the batteries, but what it does do is overheat them when the engine gets going. And overheated batteries have a propensity to 'self-disassemble', rapidly (as in, explode)... At the very least it will significantly shorten their lives. If you're going to be draining batteries, leave the standard alternator on.... Cheaper, safer.

Chris.........

 

[Scott Danforth]

achris, that is thermal reconfiguration AND kinetic disassembly.

an ACR or a DC-DC charger can charge the house batteries once underway

 

[moonrakercat]

Mercruiser Manual 3

Thanks !!! I take it the manual is in the stickies somewhere ?? I'll have to check it out !

 

[moonrakercat]

If you have a voltmeter, then this should be what you're looking for. (BIA is Boating Industry Assoc. In the late 70's Merc adopted BIA wiring colour codes)...

With an 80A or 90A upgrade (standard alternator is either 37 or 55Amp, depending on which alternator), I would also increase the size of all the wires running from the alternator output to the battery! By all means, a higher output alternator will be an advantage if you plan on using your high current consumers while under way. But if you are hoping to use the higher output alternator to recharge the batteries very quickly, that's a very bad idea. It doesn't help with how much you drain the batteries, but what it does do is overheat them when the engine gets going. And overheated batteries have a propensity to 'self-disassemble', rapidly (as in, explode)... At the very least it will significantly shorten their lives. If you're going to be draining batteries, leave the standard alternator on.... Cheaper, safer.

Chris.........

Hi Chris - thank you sir ! - that is my exact configuration - I do have the voltmeter - no ammeter and a 50A circut breaker as shown. I wasn't planning on charging the batteries any faster - I just don't want them to discharge with the engine running under my planned loads.

However you've brought up a new point - I don't see any mechanism in the schematic above that controls the battery charge rate (I will have 3 batteries charging) - so I assume it is just the alternator output and voltage differential between the alternator and batteries that will determine their charge rate ?

I was also concerned that if I had a lower output alternator and was drawing 90-100A from the batteries that the alternator would try to compensate - and possible self destruct itself. I do have an electrical background but will consider it prudent to consult an alternator/starter business for their expertise. I do definitely plan to run another conductor or two to the batteries to compensate for a new alternator output.

 

[Scott Danforth]

just a word of caution. Delco determined that about 60 amps is the max continuous output you can put out of the 10SI case with the cooling available from the fan. todays Delco Clones putting out 90 amps or 105 amps can do so, however not for a long period of time before they suffer from Thermal Reconfiguration

 

[moonrakercat]

I'm going to ask one more question - not sure if anyone knows - the alternator I have is a motorola 8rg2018 - I'm not sure if it is a 55a or a 37a unit - and searching the web brings me nothing - anyone know ?

 

[achris]

I'm going to ask one more question - not sure if anyone knows - the alternator I have is a motorola 8rg2018 - I'm not sure if it is a 55a or a 37a unit - and searching the web brings me nothing - anyone know ?

8RG2018 is the voltage regulator number, not the alternator. Look for the number 8MR2023F or MR2036K. Should be on the flat section of the frame that forms the top mounting.

...However you've brought up a new point - I don't see any mechanism in the schematic above that controls the battery charge rate (I will have 3 batteries charging) - so I assume it is just the alternator output and voltage differential between the alternator and batteries that will determine their charge rate ?

That's correct.

I was also concerned that if I had a lower output alternator and was drawing 90-100A from the batteries that the alternator would try to compensate - and possible self destruct itself.....

The inherent design of an alternator is self limiting. It will only ever put out it's maximum rated current. It can't exceed that. Unlike the old DC generators which could, would and did, exhibit a rapid and high kinetic disassembly if the output current regulator wasn't see correctly.

Many years ago I was doing a long drive at night (over 450 kilometers). The car's alternator was a 35A unit, and I was running a couple of high powered spotlights (Cibie SuperOscars)... It didn't take long before the lights started to go quite yellow. The alternator was outputting its full 35A, but with the vehicle's standard headlights and the spots, it just couldn't keep up... Point being that the alternator didn't 'make poopies in its pants'....(Also at the end of that trip, the fuel gauge was worryingly close to the bottom of the scale, and it was 1984, no 24 hour petrol shops in those days, especially along a not often used country road.. :facepalm: I had already put a 20l can of petrol in part way down too, as I knew it was going to be a close thing..)

Chris..........

 

[moonrakercat]

8RG2018 is the voltage regulator number, not the alternator. Look for the number 8MR2023F or MR2036K. Should be on the flat section of the frame that forms the top mounting.



That's correct.



The inherent design of an alternator is self limiting. It will only ever put out it's maximum rated current. It can't exceed that. Unlike the old DC generators which could, would and did, exhibit a rapid and high kinetic disassembly if the output current regulator wasn't see correctly.

Many years ago I was doing a long drive at night (over 450 kilometers). The car's alternator was a 35A unit, and I was running a couple of high powered spotlights (Cibie SuperOscars)... It didn't take long before the lights started to go quite yellow. The alternator was outputting its full 35A, but with the vehicle's standard headlights and the spots, it just couldn't keep up... Point being that the alternator didn't 'make poopies in its pants'....(Also at the end of that trip, the fuel gauge was worryingly close to the bottom of the scale, and it was 1984, no 24 hour petrol shops in those days, especially along a not often used country road.. :facepalm: I had already put a 20l can of petrol in part way down too, as I knew it was going to be a close thing..)

Chris..........

Chris - hats off to you - much appreciated on the above info -I'll check the alternator - it was redone maybe 5 yrs ago by a reputable alternator & starter business - and they painted it black - so I'll remove some of the paint & look for the #. I did call the place yesterday that redid it for me years ago and they said it's a 37A - so I'm definitely going to upgrade to sierra's 68A model which is a plug & play and run an extra wire to the batteries to compensate for the extra current drawn by the inverter.

One last question - where did you get that schematic you posted up for me ?

Thanks !! - Matt.

 

[achris]

...One last question - where did you get that schematic you posted up for me ?

Thanks !! - Matt.

Mercruiser genuine factory service manual #3, section 3F, page 39.

Chris......