STFT code, fuel mileage getting worse

[hcooperrn]

I know there's another thread on this engine code, STFT 2 High Limit, didn't want to hijack with my own symptoms so thought I would start again.

I've been getting the code for a couple of months, always starts within a couple of minutes while we're waiting for the trailer driver to get back to the dock (just idling around waiting for temps to come up). Back in late June, I could take it out, run it up to speed for a few minutes, shut it down and kill the power at the battery switch, and the audio/visual code would go away.

Late July, the code would not clear, even after several hot laps, so I took it in. They found the code history in the computer, said it was a voltage issue in the fuel system and not related to the O2 sensors, they cleared the codes, ran it on the hose, and said it was fine.

Took it out yesterday, and exact same story, code came back within a few minutes, was able to clear it for the day after the first surf session (~1 hour of surfing at 3200rpm). Power seems off, boat just feels like it's dragging. Prop looks fine, I check/feel it every trip, nothing physically noticeable and I haven't hit anything that I'm aware of.

Also noticed that my fuel economy is getting worse. I've kept meticulous records -- our season average so far (48 hours) is at 6.19 g/h. Yesterday, we got 7.51 g/h. I know there a lot of factors (how long you're up, how often you're falling, etc, etc). Looking back at the history, there's a pretty clear pattern. When I added 500# of weight, economy took a hit. On trips with more tubing/less surfing economy is better. Overall, the trend is going the wrong direction though...

So, two questions:
1) When I took it to the shop, I dropped it off with 43.8 hours, and I picked it up (almost 2 1/2 weeks later) with 43.8 hours. When they are running it on the computer, do the hours not count? Or did they only run it for less than 6 minutes?
2) I can order a set of O2 sensors, however, I don't want to just burn through those, is there a definitive cause of this issue?

[Z3 LKG]

My O2 sensors were replaced by the dealer in early May. The issue hasn't returned and wave had the boat on the water every weekend sense. Good luck!

[tigemech]

I would bring it back to your dealer, tell them it still isnt right after they looked at it the last time. Its still under warranty

[hcooperrn]

I would bring it back to your dealer, tell them it still isnt right after they looked at it the last time. Its still under warranty

Yep, that's in the plan, I'm just trying not to be a jerk, and want to avoid having it in and out a dozen times at the same time. I get that warranty work is a pain for a dealer, and I also get that I paid a lot of money for the boat, not trying to stir up that discussion at all, so just trying to be as informed a customer as I can be, while not being a PITA customer either, it's a fine line sometimes. If there were other dealers offering competition it might be a different story, however, I'm a bit limited without driving a few hundred miles...

Will gladly take any advice, especially from those of you that work at dealerships, what's the best way to have the discussion that I'm informed enough to know that something isn't right, and that clearing the codes isn't the solution, while not being insulting at the same time? I'm a nurse by training, and I'm sure it's no different than patients of mine who used to go to WebMD to tell me how to do my job...

[tigemech]

Personally the only time a customer comes off as annoying, is if they think they know exactly what is wrong, and pretty much try and tell you how to do their job, because something they saw on the internet. What I appreciate in a customer is if they tell me, in as much detail as they can what is happening with their boat, and what they tried doing themselves, then letting me do the work. In this case its a very good chance it is the 02 sensors, but you dont need to tell them that you think that. If they are worth a darn they will figure it out. Tell them that you seem to be getting worse fuel economy, pretty much everything you said in the first post is a really good start. They are going to have to run it for more than 5 minutes on a fake a lake to find the problem. Is this the dealer you bought the boat from? Is the dealer close to a body of water for a lake test?

[hcooperrn]

Got it, I'll be sure to keep my research closer to the chest.

Yes, it's the dealer I purchased from, and no, they don't have a nearby in-water test spot anymore, closest state lake for them would be about a 30 minute drive.

[freeheel4life]

Agree with Tigemech. The more info you can give then the better. If they are using Diacom they can look at bank 2 o2 sensors and I would bet this week's paycheck that wideband o2 is reading no where near stoic. Which computer then trys to fix by adding more fuel to that bank(lengthens injector pulse time) hence decreased fuel economy, and code being set.
If you want to save yourself some hassle go and get yourself one of these as you seem pretty handy
https://www.walmart.com/ip/Wilmar-W1...&wl13=&veh=sem
You can get one at any decent auto parts store.
Pull out the pre cat o2 that is in your exhaust manifold and look down the hole. If you can visibly see water on sensor or pooled in manifold the gasket just upstream where manifold bolts to cats got installed wrong at Indmar assembly plant. You can also swab around in there with a q-tip and see if you get water. Obvious signs also will be a big rust colored patch when you look down the o2 hole. There should be no water in there at all so any signs of moisture and you've found your problem.
Not to talk smack on your dealer but sounds like they hooked up Diacom, cleared your codes, ran it for a minute or two(obviously less than six)without codes coming back. Called it a day. Hour meter will run when diacom is hooked up as long as engine is running. Ask them to print off freeze frame and extended freeze frame for codes. Will show what your wideband o2s were reading and what system voltage was when code was set so you can confirm if it was low voltage or if wideband o2 sensors aren't reading stoic. Would give them benefit of the doubt as a lot of times codes will stay away when running on trailer and require engine to have a load on it.
Diacom gives you a ton of info but if you don't know what expected values should be it is hard to interpret data that you are getting and using that data to come up with what problem is or where to look.
Regardless I would suspect water due to misaligned gasket at manifold. Easy fix and cheap parts.

[hcooperrn]

I pulled my post-cat sensors (top of the engine, easy to reach), there was definitely rust on them and even on the threads. I'll take a look at the pre-cat.

When people are replacing, is it the pre or the post, or both?

[freeheel4life]

Pre cats. These are your widbands(blue sheathing). Pull them as that's where water will collect. Just replacing isn't the answer if you have water. They are easy to get to as well.

Btw bank 2 is cylinders 5,6,7,8(ford cylinder numbering is entirely different than GM on these engines) and are starboard side so look closely at that side exhaust manifold.

[scoot18]

I am one of those other owners talking this same issue on another thread here, I have the same DTC and issue as you, We pulled the bank 2 sensor and it was wet. Bank 1 was okay, all dray. The shop owner told me that Indmar has had an issue with welds on the elbows that connect the manifolds to the cats and that is the route cause for the water getting in. There could be a gasket issue as well, but it is an internal weld on a baffle that is internal in the elbow that is causing all of the issue. Not likely that the sensors alone will correct the problem long term. Each situation can be different, but in my case the elbows and both sensors will be replaced, currently waiting on parts, hope to have this completed this weekend.

[freeheel4life]

Scoot-
I haven't taken any pictures of one but the aluminum gaskets that I've pulled out on all three boats that have had this problem were obviously misaligned. You could see it in the way the gasket got crushed after you pull it out of there. It is very difficult to keep gasket aligned after you start to put v band clamp back on.
https://www.jbtoolsales.com/permatex...EaAqA_EALw_wcB
I have been putting a heavy coat of this on gasket and exhaust manifold and letting it set up a bit before I bring cat manifold and v band clamp to the party so it can't shift during assembly.
Not sure about weld issues but could be. So far I know the three boats I've repaired haven't had any o2 sensor or STFT codes since. The gasket is a whopping 4 bucks from indmar I believe so if you are removing v band it's worth replacing regardless.

[scoot18]

Scoot-
The gasket is a whopping 4 bucks from indmar I believe so if you are removing v band it's worth replacing regardless.

I'm not sure if the dealer (dealer owner) is ordering those gaskets also, I imagine he would, when he checked my boat it was if this wasn't a new discovery, like he has already done this a few other times before on other boats. Looking at the elbows, they don't appear as if they would be that much trouble to replace, with the exception of this gasket placement and alignment per your experience, do you know if that is the case? I am trying to encourage the owner to do it at the dealers Lake location which isn't where the service facility is, in an effort to keep from having to tow it home and then to the dealer, 2.5 hrs each way; so I asked him if he'd be willing to do it at the lake shop and I would help him. Ideas?

[freeheel4life]

Not 100% Sure what elbows you are talking about so don't want to speculate. Are you talking about the problem being at the flange where cat manifolds meet exhaust manifold in relation to weld?? Only real issues I've seen so far with cat manifolds from indmar was in relation to their double wall tubing. At top where they turn down to YPipe the inner exhaust wall would get to close to outer wall and would get hot and start to cook powder coating. This was only a couple early model raptor though and believe indmar most likely figured it out as they make these cat manifolds in house.
If you follow water flow from front of engine it will become clearer how this whole system is working. Also helps to pull boots at y pipe and look in to understand, if you are the curious type, that water and exhaust dont intermingle until this point. Those boots are also directional and have to be seated just right so if they get removed note orientation and factory installation to make sure they are installed correctly when putting back together. If you are just replacing gaskets though it is not necessary to even touch those boots though. Starboard side is tougher job due to location of fuel pressure sensor unit location. Port side access is way better.

BTW should mention that we have sold a lot of Tige and Skiers Choice boats this year and have only seen this problem on three boats, so while there is some rumblings about this here on the forum would still say indmar is knocking it out of the park. Don't know of any manufacturer with 100% perfect turnout

[LTWellman]

I've been getting the same SFT 4238 code for a month. My dealer came out and did a software update and claimed it to be fixed. I told the tech about what others were experiencing and he told me, we've had great luck with what he had done to fix the issue....5 minutes away from the dock, guess what came back.
Needless to say I'm not pleased. I had a 2008 BMW M3, it had a ton of issues, the BMW dealer would be like, we updated your software and you're good to go, 10 miles down the road, it'd pop off the same faults...I'm not a believer in software update fixes.

[hcooperrn]

Got it back Friday, they replaced the O2 sensor, ran all day without a code, SOTP felt much stronger, rpms were lower while surfing (just over 3000), and fuel economy over 5.3 hours of run time came in at 5.27 gallons per hour, much better.