Swapping out the old transducer (888828A21) with new one on 2011 Sundeck 260

Sep 24, 2022
Boat Info
2011 Sea Ray Sundeck 260
350 MAG/Bravo III
OK...my SmartCraft depth gauge is very inconsistent. Most of the time it gets stuck on a depth and just flashes at the depth or just shows 0.0. My assumption is it's on the fritz. The water temp comes in and seems accurate enough. Mercruiser doesn't make the 888828A21 any longer and and I think this will be a good replacement:


What's weird is the old transducer says it's a 20 degree which I think is generally placed off center where the the 20 degree angle better matches the angle on the hull. Mine is on the keel, right on the centerline so the 20 tilt doesn't make any sense. Probably won't matter much in shallow water but if I'm buying a replacement, might as well get one that makes sense.

So, now for the varsity question. I have the original SmartCraft gauge (tachometer with the SmartCraft display). On the same website, I saw this for a few bucks more:


It's a triducer that has temp/depth/speed (via a little paddle wheel). I'm wondering if this would be compatible with my 2011 SmartCraft system? Anyone try and upgrade theirs with the setup?


Mercury Marine customer service stated that my Smart Craft system (350 MAG EC DTS) is compatible with the Triducer (8M6004807). I bought one and I'm looking at it. The regular temperature/transducer combo only has one wire coming out of it but this one has two. One has a sticker on it that says "connect to engine diagnostic connector". Now it has the same color wires as the old temp/transducer so I think that this wire will be a one-for-one swap of the old one coming off the old temp/transducer.

The sticker on this one reads as follows:

A. BLK Ground Supply Voltage
B. BLU RS485+
C. WHT RS485-
D. PUR 12VDC Supply Voltage

The second wire sticker says this, "Paddle Wheel Connector, connect to boat harness".

A. BRN Speed/Temp Ground
B. RED Speed Voltage
C. GRN Speed Signal
D. WHT Temperature

I'm not really sure where to connect the second wire that says to connect to the boat harness. I can't really find anything that says that in my owners manual. I'm hoping it'll be obvious when I try to install tomorrow.

Anyone have any ideas?
How did the swap go? My transducer is the same as yours. Temp seems very accurate, depth just flashes 0.0. Did everything fit well with the existing hole? Thanks!
The triducer was a form/fit replacement for the old transducer. The transducer cable (different than the paddle wheel cable) just plugged into where the old cable went. There was some wire bundle wrangling but everything went together well. I did need to adjust the depth reading on the smart craft gauge. Mine was showing about 5 feet too deep. Adjustments are by the foot so close enough needs to be good enough. I will post more tonight when I get home detailing the process.
Ok...here goes.


I replaced a 20 degree transducer/temp sensor with the TRIducer pictured. The old transducer (part 888828A21) was a 20 degree, made to be placed off center on a V-hull. My Sundeck has the transducer right on the keel so no need for the 20 degree. It should be a zero degree.

That part number according to Mercury Marine is 8M0122507 for a zero degree direct replacement.

For about $40 more, the triducer adds the paddle wheel speed sensor which should allow for some extra benefits like troll control or perfect pass if I want to upgrade the Smart Craft gauge. I figured for $40 more, why not? In the picture, the long cable is the transducer portion and that plugs into the engine diagnostic harness on my 350 MAG with DTS. That sits on the top of the engine, near the 50 AMP fuse. There is a 2 AMP fuse holder that goes between the transducer connector and the engine diagnostic connector that looks like this:

Your boat should already have this so the transducer part is pretty plug and play.

The depth adjustment is easy on the SmartCraft display (SC1000). It's easy to download the manual online but to get to the calibration displays, just hold down the MODE and + buttons at the same time until you see CAL1 or something like that. There is CAL 1 and CAL 2. The depth menu, I believe, is in CAL 2. It's fairly self explanatory when you see it. I used a string with a weight to measure the depth at my slip, then lowered the boat lift until the transducer was just in the water. Water depth measured a hair under 8 ft. The transducer was showing 13.5 ft so I took 6 off so it shows 7.5 ft. I'd rather it be more conservative-shallow than deep. There are people who want to know actual depth but I preferer to know how much water is under the keel. These menus are also where you set the depth alarm. I adjusted mine to 3.2 ft. to give me some margin. The odd part is the depth adjustment is in 0.3 ft increments but OK...I didn't build the thing. Must have been a reason for that odd increment.

The smaller plug on the triducer is to provide paddle wheel speed to the SmartCraft network. I have no idea where to plug that in. The transducer part is about 10ft long and easily worms it's way around the engine bay basically following the route the old transducer cable followed which was very plug and play.

Mercury Marine sent me this regarding the paddle wheel plug:

The paddle wheel will plug into a vessel connector for fuel and paddle and is a 6-pin fuel harness used for fuel sender to SmartCraft Fuel Level and is shown below.


However, we are confused by this question because if replacing a triducer with a triducer, the connections should all be there.

It's not Mercury's fault per say for not understanding that I'm adding the paddle wheel. But how does a 4 prong connector plug into the 6 prong plug? Since the paddle wheel sensor cable is only about 12 inches or so, I believe I'm missing an intermediate cable that will plug into what Mercury calls the "vessel connector". I do like that all the cables are labeled, kind of like the Bat Cave in the 1960s Bat Man, but I can't find one called the "vessel connector". They do mention that it's the plug that comes off the fuel tank which is easy to find but that cable disappears into the spaghetti of cables rather quickly.

I'm resubmitting my question to Mercury with a clarification about not replacing a paddle wheel but adding a paddle wheel. When I get that sorted, I will post here so everyone can know how to add one without giving up a kidney to their local marina. Kudos to Mercury Marine! My experience has been pretty good with them explaining stuff to me when I ask a question. Not sure everyone has the same experience but they've been on point with me!

In general, changing a transducer is easily done and boat owners should not be afraid to do it. They are about $350 on average from what I've seen. No reason to have a mechanic do it unless they throw it in with other maintenance. The piece with the orange sticker is a plug to quickly put in to keep your boat from taking on water while you switch the transducer out. So swapping a transducer can be done with your boat in the water. Mines on a lift so I didn't need to worry about it.

Hope this helps someone out there who is thinking of doing this work themselves.
Update! I was able to get the paddle wheel hooked up and working. I needed to get a new harness, part number 8M0075945. I found the paddle wheel plug on top of the engine near where most of the other wire bundles plug in. It only had one pinkish red wire plugged in to feel the fuel tank info to the Smart Craft gauges. The process was simple. I just unplugged the plug that was there, and plugged the new six conductor wire harness in. The fuel tank lead had a three conductor plug of which there were only two conductors being used (signal and a ground). I spliced in the fuel wire from the new harness in and all is well!

You'll need to turn on the paddle wheel sensor in the settings on the SC1000 so it know to use it. Worked great as far as I can tell.

As a side note, I find it weird that the SC1000 that came with my boat has troll control and not Smart Tow. Seems like Smart Tow would have been a better option for a family boat that is designed more for water sports than for trolling. I have a new SC1000 on my list of upgrades that can use smart tow.
This is great! Thanks for posting all of the details! Finally going to replace mine today, will see how it goes.
About the SC1000 - mine has a sunburned area on the lcd. I see that there are places online to refurb or replace the lcd. How do you get the gauge out? Is there a way to access the area behind the gauges from the area by fuses, or?

I didn't take the guage out. But it seems accessible through the hell access panel in little cabin just forward of the helm. My current SC1000 tachometer's LCD has no issues. I will swap it out with a MercMonitor (79-8M0135618) that has tow control maybe next spring. Towing some wakeboarders this summer convinced my wife it was worth the money. Or at least she nodded her head when I mentioned it. I'm sure when the time comes to spend the money though...

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