Problems with brand new Mercruiser 383 MPI

[alldodge]

If you did tulip one valve then there would be an issue with an injector

Red/Purple is main power after the motor breaker. No way that wire should be cut, need to find the other end

 

[Rogerdog23]

Thanks AllDodge. I’ll try to track down the other end. Any ideas where to look? I believe there are two red / purple wires to that plug if I remember correctly. Do you know the function of the wire and it the boat should even run without it?

 

[alldodge]

Red = direct battery connection
Red/Purple = battery voltage after 50 amp breaker

The Red/Purple goes to several places, and then to thru other fuses (changes colors) and on again

 

[Rogerdog23]

AllDodge, can't tell you how much I appreciate you taking the time to find the wire diagram and send it to me. I gave it the old college try and couldn’t find any missing wires but fully admit I’m not able to track what exactly I’m looking for from the diagram. I found a diagram from Mercruiser for my engine that would give me a real shot at tracking the wires as it shows what the connectors look like where the wires terminate. Unfortunately the file is too big and I cant upload it to the site. I'll try to send you a PM with it and see if it works. The diagram number is 865454A01.

 

[alldodge]

I got it thanks, that is a big file, will save it future use

 

[Rogerdog23]

Great. The more I thought about it I’m thinking the cut wire must go to the 50 amp breaker not the starter fuse since the wire is red with purple stripe. I understand the wire changes color but since it’s red / purple where it is cut I’m guessing the other end should be the same color. Sound right? Also I’m guessing the engine wouldn’t run if it was the starter fuse.

I will head to the boat soon. Any other areas I should check out? The cut wire is quite long and is coiled and zip tied back where several wires come together near the round plug. It’s still long enough to go to the flame arrester even with the zip tie. I hope it doesn’t go under the engine or something crazy.

 

[alldodge]

Yes, Red from battery to 50 amp breaker, and Red/Purple after it

 

[alldodge]

Using your drawing Red/Purple comes from 50 amp breaker which feeds
MPR pins 30 and 86
Slave relay
Pin 6 engine plug
ALT field
Fuse 2 (which passes to Pink Lt Green for FPR, CAN connector, ALT sense and others)

 

[Rogerdog23]

The plot thickens...

Found a cut wire on the mercathode. A ring connector with a rubber boot over it. Upon closer inspection the cut wire that went to the ring connector was Red with a purple stripe. Is there supposed to be a red with purple going to the mercathode?

When i first found the cut red wire a week or so ago I couldn’t get a good look at it and said it was a cut red wire (I didn’t know there was a purple stripe at the time). Muc guessed it would be for Mercathode if it was plain red. In the wire diagram I sent AllDodge I only see reference to a ground wire for mercathode, not a hot wire.

Questions:
1. Does the cut red / purple wire belong on the Mercathode?
2. If not, is another wire needed for the Mercathode before it will function properly?

If it doesn’t go to the mercathode then where does it go?!

 

[alldodge]

I would say yes that is the mercathode (MC). The MC use to be red and it would tie into a battery connection. Looks like Merc decided to mode it to the other side of the 50amp breaker

 

[muc]

pretty sure it might have gone to the Mercathode.
should be 4 wires to the Mercathode.
only the ground wire usually shows in the wiring diagram, guessing that's a hold over from the days that it was an option.
what color are the wires going to it now?
Some boat manufacturers will cut the wire in the engine harness and use a wire from the "always on" power (the power that will also go to the float switch and radio memory). So the Mercathode has power when the battery switch is off.

 

[Rogerdog23]

Thanks—Here’s a pic of the wires going to the Mercathode. What think?

Sounds like we might be back to the drawing board. Not seeing any improvement in performance and if there is a fuel improvement then it is quite small. The VesselView shows me running at 158 degrees most of the time at cruise. When i go WOT the temp usually goes down. Have a pic showing 153 degrees at WOT 4920 rpm. Another pic at WOT showed 158 degrees.

 

[alldodge]

Yep, thats where it goes

 

[Rogerdog23]

So hook it back up or is it redundant? Would if be cut at factory or dealer?

 

[muc]

Your Mercathode isn't working right now.
If you use the wire in the harness, it will only work when the battery switch is on.
If you want it to work with the battery switch off (almost everybody does) it will need to be wired to battery + before the battery switch. Will also need a 5 amp fuse. This wiring is in most boats. The installers of your engine should have connected this. It's part of every engine swap.

 

[alldodge]

Question: Do you have a mercathode anode under the drive?

If not, maybe that's why it was cut.

 

[Rogerdog23]

How bad of a power draw is it with the battery off?

Will the engine get full performance if the temp gauge on VesselView is reading 160 or hotter? Or is there a better fuel table that kicks in at higher temp?

Sounds like it’s time to go back to the deal and see if they can find a solution.

thanks guys.

 

[alldodge]

Its low (less then 1 amp), but its best to keep battery on a charger

 

[Rogerdog23]

Thanks AD.

Not sure if i have the anode. Can look when I haul out of the water. I think it’s time to get a TAM out here from Mercruiser to take a look. Still burning 16.5 gallons an hour at cruise. About ready to fix the valve on the old Engine and put it back in there. Grrr. At least a problem with a pleasure boat isn’t really a problem in the grand scheme of things...

 

[Rogerdog23]

Talked to Mercruiser today. They want the dealer to do a water test with recording and have the full report sent to them so they can take a look. If that uncovers a fixable problem we’ll explore it, otherwise I’m headed for a refund. Will keep folks posted on what I learn later this week.