MDC Delete and Gauge Replacement

[Jeff d]

I'm getting the boat ready for summer and recalling all of the bizarre behavior that my gauges have given me for the last 3-4 seasons on my 2000 230 VRS. I've had issues with every single gauge on the dash at one time or another. I "fixed" the speedo by removing it and putting in Perfect Pass. I have already pulled everything apart, cleaned all connections with contact cleaner and reassembled with no improvement. Grounds and connections at the MDC are all good. I've tried disconnecting some of the gauges to see if one particular one was creating noise on the MDC bus without success.

My OE gauges aren't very common so it's not easy to find a replacement if I even had the desire to try to figure out which one or ones are actually bad. I have black chrome trim rings and antique white faces. Currently my Perfect Pass gauge doesn't match anyway and the depth sounder didn't match from the factory.

So, I think my best and cheapest option might be to just ditch all of the OEM gauges and wire up a decent aftermarket set of gauges directly to the harness that currently plugs into the MDC, bypassing/eliminating the MDC. I'd then just have individual gauges talking to individual senders instead of this difficult to troubleshoot bus system where all of the gauges are controlled via one set of wires.

I could pickup this set for $170 and then sell off the speedo (Since I don't need it or have the space for it) to recover a few bucks:

http://www.boatersland.com/farktf001.html

It's cheaper to buy the set with the speedo then to buy the rest of the gauges that I actually need individually.


Thus far the senders I've dealt with have been pretty standard relative to boats and even cars with GM V8s. When I had a bad oil pressure sender I just picked up a pretty standard one at Napa and it worked so I'm probably good on oil pressure. I'll have to research the ranges on the senders for fuel level and engine temp. Tach shouldn't be an issue because I was able to just tap a wire under the dash (Pre MDC if I'm not mistaken) for my perfect pass to pickup RPM without issue. There's obviously no voltage sending unit so the voltmeter should be plug and play. The depth sounder currently doesn't pass through the MDC at all so that shouldn't be an issue.

What controls the "Check Engine" light on the dash and if it is the MDC how useful is that light to begin with?

That Faria tach in the gauge set doesn't include an hour meter but my Perfect Pass has that so it's not really needed.

What, if anything would I be giving up if I eliminate the MDC and the medallion gauges?

[Bruce-ActionWater]

If you don't have the speedo hose hooked up the the MDC it wont fail again. That is what we do here at our shop.

[Jeff d]

It's still about 1/2 the price to replace all of the gauges with aftermarket, standalone gauges vs. replacing the MDC. Also, unless I had a known good MDC to test with I can't be sure that's even the problem. If I buy an MDC and then it turns out I had gauge issues too I'll be at $400-500+ pretty quickly.

[Jeff d]

Tonight I spent about an hour pulling the dash apart, cleaning connections and troubleshooting the gauges again per the Medalion troubleshooting guide. I got erratic behavior from both the fuel gauge and the temp gauge even if those were the only gauges connected to the MDC at the time. I'd turn the key on and the fuel gauge would "reset" and say the tank was empty. I'd then turn the key off and back on and it would say 3/4 tank. Once I turned the key off and back on and the needle went all the way around to where it indicated that I had about 1.75 tanks of gas (i.e. way past full). I didn't test the sender again tonight but I've tested it before and as I moved the sender in and out of the tank the resistance moved appropriately on my multimeter.

I think I'm going to proceed with the Faria gauges. The limited number of reviews I've found on them were overwhelmingly positive with only one negative. I've confirmed that the fuel level and oil pressure senders are correct for the Faria gauges. From what I've been gathering the senders are pretty well standardized on american boats so the water temp sender is more than likely correct too. Worst case, Faria makes a compatible temp sender if I need to swap that in.

I also tested that the check engine light and the alarm both work (Or at least illuminate and make noise when the key is on) even when the MDC is completely disconnected from the electrical system. So it seems that those don't pass through the MDC. Also the engine starts and runs without any issues with the MDC removed.

[ProStar Slalom]

Good for you, Jeff. Plenty of us have had to replace the black box and/or a gauge or two. Please keep us posted on how this turns out.

[73blue]

I will definitely be monitoring this thread. I've been having gauge issues in my 04 and would possibly be interested in bypassing the black box as well

[Jeff d]

I'm still trying to figure out what I'm missing here before I jump into this. If all the MDC does is gather data from the standard senders and then translates/dumps it onto a bus for display on the specialized gauges what's the point? That seems needlessly complicated and expensive relative to more standard gauges connecting directly to their respective senders. What's the appeal of the MDC/Medallion gauge system to OEMs? It's not just MasterCraft that uses this arrangement. I know at least Malibu used the same setup.

Does anyone have any idea if the MDC provides some sort of alerts based on engine conditions? I had an oil pressure sender failure a couple of years ago and the MDC didn't alert me in any way. As far as the MDC knew at the time I had zero oil pressure so I'm safely assuming it does not monitor those sorts of critical conditions. It has to add some value right? It doesn't seem like it would be easier to install for the OEMs during manufacture as, if anything, there's more wiring associated with this arrangement. It can't be cheaper can it?

[geordie-wake]

My 99 205v has gauge chatter and I have just replaced the temp gauge since that doesn't zero anymore and it still doesn't function correctly (last option new MDC or replace with Faria or equivalent). There was a 2000 X-star advertised for sale over here in the UK that had been converted over to Faria gauges and now I know why. How can you be sure they are reading correct. My first boat was a 1978 inboard with the original smiths gauges and no problems at all the second boat on a mercruiser engine also had no problems with gauges but these Medallion sets I just don't see why MC persisted with them.

[Bruce-ActionWater]

Tonight I spent about an hour pulling the dash apart, cleaning connections and troubleshooting the gauges again per the Medalion troubleshooting guide. I got erratic behavior from both the fuel gauge and the temp gauge even if those were the only gauges connected to the MDC at the time. I'd turn the key on and the fuel gauge would "reset" and say the tank was empty. I'd then turn the key off and back on and it would say 3/4 tank. Once I turned the key off and back on and the needle went all the way around to where it indicated that I had about 1.75 tanks of gas (i.e. way past full). I didn't test the sender again tonight but I've tested it before and as I moved the sender in and out of the tank the resistance moved appropriately on my multimeter.

I think I'm going to proceed with the Faria gauges. The limited number of reviews I've found on them were overwhelmingly positive with only one negative. I've confirmed that the fuel level and oil pressure senders are correct for the Faria gauges. From what I've been gathering the senders are pretty well standardized on american boats so the water temp sender is more than likely correct too. Worst case, Faria makes a compatible temp sender if I need to swap that in.

I also tested that the check engine light and the alarm both work (Or at least illuminate and make noise when the key is on) even when the MDC is completely disconnected from the electrical system. So it seems that those don't pass through the MDC. Also the engine starts and runs without any issues with the MDC removed.

The MDC is only for the gauges. The check engine light it ran off the ECM.

[M.T.]

Outlaw marine was installing these gauges on a x7 last year. Don the owner said it is the way to go. You might want to give him a call 352 475-1229.

[Jeff d]

I think I've got it figured out but it's good to hear that I'm probably on the right track here.

I haven't actually found an inboard specific MDC schematic but the one for Outboard applications seems to match up with what I have with the obvious exception of the trim gauge.

18 Pin Connector (Mostly unused BTW):
Red (1A)- Constant +12 volts
Purple (1B)- Ignition Switched +12 volts
Tan (1C)- Temp
Blue (1D)- Oil Pressure
Pink (1E)- Fuel Level
Black (2C)- Ground
Gray (2D)- I think this is tach signal

There's also supposedly a blue wire that connects to each gauge from the Nav light switch to turn the backlight on/off. I'll retain that wire but trash the rest of the 3 wire bus harness (5 pin connector). It seems pretty straight forward from there. Daisy chain ignition switched +12v, ground and the Nav light switched +12 volts to each gauge. Then connect tan to the water temp gauge, blue to the oil pressure gauge, and pink to the fuel level gauge. I don't remember the color for the tach signal wire and it's not labeled on the MDC schematic but I think it's gray.

It looks like I may even have enough slack in the wiring that I won't have to splice in extra length to reach the new gauges once I cut the 18 pin connector off.

[02ProstarSammyD]

Irony.......I'm trying to get my rpm, temp, etc hooked back up to factory gauges and you are going the other way

[19_Skier]

Can't wait to see how this turns out for you. My factory gauges look like crap, all cracked. Getting rid of the MDC and gauges for considerably less cost than purchasing new MC gauges (which are ridiculously overpriced!) would be great.

[ncskier]

That Faria tach in the gauge set doesn't include an hour meter but my Perfect Pass has that so it's not really needed.

Do both the Perfect Pass and the MDC track the hours internally? A friend recently replaced his MDC and I thought it set the hours back to zero. It would be nice to be able to reset them if the only way to get the actual hours is from the ECM.

[Jeff d]

My understanding is that there are up to 3 runtime clocks all running independently. There's one in the ECU, one in the MDC and one in the Perfect Pass. Perfect Pass didn't implement an hour meter until a certain hardware/software revision a few years ago. Mine has it and I know it's operating independently because when I installed it I had to enter the starting value.

Here's how I view engine hours on my Perfect Pass:
Press the MENU button and the UP arrow button simultaneously, then scroll down to SYSTEM INFO and press MENU.

So, if I give up the tach hour meter it won't be there staring me in the face when running the boat but it is fairly easily accessible. It costs a decent amount more to get a tach with hour meter because they don't seem to sell them in the sets. Not only would I pay more for the tach but then I'd have to pay more for each gauge because they're all more expensive when purchased individually.