Transmission Sensor or ECU Limp Mode?
So I took some friends out this weekend in my '96 Prostar 205 LT1 for some tubing and fun. The boat ran normal as I was driving over to the spot where we usually tube on the river, I ran it through the motions mostly just to test it out and get used to it as it is only my 3rd time taking it out. I started off from idle and took off like I was pulling a skiier then cruised at about 3500rpm for a little bit and then took it up to about 4800 for about a minute just to make sure we were good at all speeds. After turning the boat off and swimming for about 30 minutes we got back in to tube. I was pulling a friend of mine who is about 240 lbs and his girlfriend about 110 lbs so not any crazy load. I took them through the first run for about 5 minutes of non aggressive tubing I'd say a 4 out of 10 on the tubing scale. Then the 240 lb'er decided he wanted to go on his own and challenged that I couldn't throw him off. So naturally I took the challenge and swung him back and forth at about a 7 out of 10 but never really exceeded 3500 rpm doing so. I was however powering through some turns. After about 2 or 3 minutes of pulling him through this I noticed I could not power over 3000 RPM's and when I tried to do so it was like the boat was keeping me from doing so, as if it was in a "limp mode". It didn't necessarily feel like the transmission was slipping just that it was keeping me from accelerating past 3000. So I took it out of gear and in neutral and the engine would rev up to 4800 RPM as it should. I also noticed at this time a whining sound coming from the bilge. I pulled the engine hatch and it sounded as if it was coming from the transmission. I then turned the boat off and immediately turned it back on, the whining stopped and the boat functioned perfectly. About two minutes later as I ran back down the lake I noticed the whining slowly getting louder from the bilge and again it would not go above roughly 3000 RPM. So I turned it off and back on again and it ran just fine again for another few minutes before having the same problem again. I checked the vitals of the engine and none of them were abnormal. Temp was about 120-140 the whole ride.
So from the circumstances that I encountered, it doesn't seem like clutch plates or anything like that. I am almost wondering if it is the pump that is for some reason not pumping enough fluid and there is a sensor that is putting it into limp mode, but I am not getting any Trans Temp light warnings or Check Engine lights coming on at all. I checked the fluid and it is at the perfect level. I am using the Dex/Merc fluid that was changed just prior to this launch btw. I have the Hurth ZF 450D. Does anyone have any advice for diagnosing the problem? Could it be excess vibration and a sensor that is causing it to limp? It seemed to be brought on by powering through turns (not power turns just normal tubing driving). The part that I am somewhat relieved by is that after 'resetting' the engine by turning it off and on it seemed to fix it at least for a minute which I am hoping is a sign of an easy fix and not a rebuild. Any help or advice would be appreciated. Sorry to be long winded but I figured if I armed you guys with all the info I had it may be easier to diagnose.
Last edited by Tateau18; 06-03-2013 at 05:55 PM.
Reason: Forgot to add some information.