'84 3.0 wiring

[will.s]

Hello. first time poster here. Glad to be here.

I have searched and searched.. I thought I had found the correct wiring diagram for my 1984 model Mercruiser 3 (SN 6806089), But I dont think I have the correct one.

My boat runs, it actually runs good except for the blown head gasket which I need to fix this winter.

I had a terrible bogging problem that occurred only when the engine got hot. After days of research, I thought the culprip was the ignition coil. I changed it out a voila< its fixed!

Im an electrician by trade, and a very detail oriented person. The wiring diagram I got shows 4 wires going to the alternator, but my engine only has 2 wires on the alternator.

I cant imagine paying for a whole book when all I need is the engine wiring diagram. Does anyone out there happen to have the wiring diagram for my 1984 model mercruiser 3.0 engine. it has the alpha 1 drive if that helps. its mounted to a 1984 model Thhundercraft, Malibu.

Thanks in advance!

 

[Scott Danforth]

welcome aboard

you can look up the manual for free http://boatinfo.no/lib/library.html#

 

[alldodge]

The wiring diagram I got shows 4 wires going to the alternator, but my engine only has 2 wires on the alternator.

Don't know of any ALT which uses just two wires other then a one wire ALT that also has a ground wire. Being an 84 your motor is listed as the 140 and wiring is below. Note BIA is the standard boating industry wire colors which started in the 80's

 

[Bondo]

My boat runs, it actually runs good except for the blown head gasket which I need to fix this winter.

Ayuh,..... Welcome Aboard,... If ya continue to run it, you'll probably ruin the head, 'n block,....

 

[will.s]

Thanks Scott, for the link. I'll check it out.

Thanks Bondo, for the warm welcome, and the warning. My block was busted and I JB welded it back together after grinding and drilling. Its holding up but now I'm seeing water from the point where the head meets the block. Honestly, I'm hoping its the gasket, and not another crack..

Don't know of any ALT which uses just two wires other then a one wire ALT that also has a ground wire. Being an 84 your motor is listed as the 140 and wiring is below. Note BIA is the standard boating industry wire colors which started in the 80's

Thank you, AllDodge for taking the time to find and upload these diagrams. They are much closer to what I'm seeing in my boat, than the diagrams I found in google images.

I do have a 1 wire (with ground) alternator, like you mentioned (see pic). Do you think it not original? if so, how do you think it will affect anything? Rather, do I need those other alternator wires?

Seems like a noob question coming from an electrician, but I just don't understand it all yet.

 

[Scott Danforth]

regarding your block. I would hope and pray, however most likely the block is toast.

that wiring to the alternator is woefully undersized. that crimp is very poorly done. I bet that wire gets almost red hot.

 

[alldodge]

The ALT is not original and Yes that is a one wire. If it works your OK but there have been many which have had issues with those (including my self, have one used one season removed and its still sitting on the shelf). So long as they insulated the power and sense leads you should be good so long as it works

 

[will.s]

The ALT is not original and Yes that is a one wire. If it works your OK but there have been many which have had issues with those (including my self, have one used one season removed and its still sitting on the shelf). So long as they insulated the power and sense leads you should be good so long as it works

Ok, so how does the wiring diagram change due to having an aftermarket alternator? I guess I'll trace it out to see where that red wire goes. I honestly couldnt tell you if its working or not, as I havent tested it.. I charge my battery every time I get back home, and I have a separate battery for my radio. I generally stay out for 4 or 5 hours and never had an issue with the battery yet.

Also, Is this a good place to inquire about which head gasket I need, or should I start a new thread? Mercurymarine.com parts catalog doesnt recognize my engine serial, and I just dont know which one fits.. I see more than one head gasket for a 3.0.

Thanks again for the help!

 

[alldodge]

When a one wire ALT is used, the Red/Purple and Purple wires are not used. So if your ALT is working your good, but if its not, it needs to be changed.

Could use your serial number to verify, but the 1984 181 cu in (3.0) is listed as a 140 HP. The link below shows the head and gasket 27-52364 (item 23)

http://www.mercruiserparts.com/bam/subassembly/30893/963/280

 

[will.s]

When a one wire ALT is used, the Red/Purple and Purple wires are not used. So if your ALT is working your good, but if its not, it needs to be changed.

Could use your serial number to verify, but the 1984 181 cu in (3.0) is listed as a 140 HP. The link below shows the head and gasket 27-52364 (item 23)

http://www.mercruiserparts.com/bam/subassembly/30893/963/280

That link is exactly what I needed. Thanks a lot! Looks like I can find whatever I need there.