Mercruiser, the big round harness plug..
 

Went to plug the big round harness into the newly wired Merc engine harness, problem is my 1988 boats harness is off by the addition of another larger pin. Nine pins in total, 3 larger than the rest. The new Merc engine harness will accept only 2 larger pins. The odd pin looks like an 8 gauge red coming from the fuse panel. did Merc change the harnesses?

Welcome to the club Dan! Seems like everything I do to get my engines set in my boat I run into all these little problems something like what you are experiencing with your wiring harness.

Oh crap I hope that does not happen to me tomarrow!!!! :(:(

The plugs have come in 3 variations that I am aware of, but there may be more. 8 pins, and 2 with 9 pins. One is numbered 1 thru 9, the other numbered 1 thru 8 and a #10 pin (#9 missing)

Dan, to anwer your question yes the harness has changed. The 88 harness uses an ammeter so there is a feed and return to the dash that completes the circut from the alternator to the battery. The new engines use a voiltmeter, much better set up.

thanks. I'm hard wired on both sides. The engine harness was 6 hours of cut,solder,heat shrink of 2 full MSD's, times 2 for the engines. Engine plug is 9 pins. Is it just the extra larger pin thats different? I'm assuming I'll need 3 schematics to compare.

When we pulled/installed the motors in my boat several of the pins in the Merc plug were loose and a couple came out. Merc wants a ton for them, plus they no longer had the early version that my boat used.

Rather than re-wire everything from the panels back with new Merc plugs (harness wires are not removabel) I just bought some mil style round connectors (which have replacable pins in case there is ever a problem in the future) and replaced both ends. All it takes is a little time crimping the new pins onto the wires and then installing them into the connector bodies. The new plugs include heat shrink back shells for wire strain relief and gaskets to keep them water tight.

-Greg

well, found out there is an extra pin,so, break it off and the harness plugs in. Except the pin was the feed to the fuse block under the dash. Can these plugs be rebuilt or replaced? The pins are knarly enough to be crimped and pushed back throough. I'll be usung a but connector and heat shrink to get it fired on the hose but need a permanent fix. Thanks

Can you just run a jumper wire up to the dash for now? I am curious as I am going through the same problem. HOWEVER my ignition does not get its power from the harness so maybe I can do the same thing? I will look into it. I will definatly change over the wire like Next week but man to have to rewire the dash with the new harness will suck!!!! I was looking at it yesterday and thinking that MAN this is so close to going in.

Jon

Nope, that's why I went with "servicible" aftermarket plugs. Was able to mount it in the same bracket by just drilling a new bolt hole.

-Greg

Greg were did you get yours?

Digi-Key. Look at the AMP circular plastic conectors Series 4 shell size 23. The 23-13M has a mix of large/small pins suitable for the required high current and low current connections on the boat, and will leave you some extras if you add other sensors/connections later. They still aren't cheap (probably $30-40 per motor for all the pieces), but much less than the Merc ones, and since they are repairable IMHO better than the Merc ones.

You need a square flange receptical body (for the motor bracket), free hanging plug body, male pins and female sockets (two different sizes), heat-shrink backshells and a pin removal tool (if you want to remove/repair a connection later on). All of the pieces are listed/sold seperately, but it's pretty easy to figure them out, just follow the notes as to which pin or socket goes with what connector series.

You should always put "sockets" on the boat and "pins" on the engine. This is of course opposite of what Merc did, but with sockets on the boat there is no chance of accidentally crossing two pins and causing a short (ie. always put "hot" connections on socktets). Drop me an e-mail if you need any details.

-Greg

Greg, if it wasn't my race boat I'd build out the harness your way. Problem is its the race boat. Engines go in and out and ignitions may change. I want to be able to use Mercruiser parts and not have to break down the wiring each time. Jon, I'm going to send power to the feed and run a seperate 8 ga ground. It'll get me to the races next week.