04 Supra Launch (Temp Gauge Questions)

[tadsell23]

I have read on the forum of a few things to check and I just can't seem to figure it out! I had the boat winterized at the Supra dealership last November and didn't have any issues with gauge last summer. I summarized boat myself and took it out and noticed that the gauge wasn't moving off 100*.

I disconnected the wire to the sender and grounded it to the block briefly and noticed the gauge began to spiked. (Out ruling gauge)...I thought!!!!
So, I replaced the sending unit with a replacement at Autozone? Took the boat back out and I still have the same problem. Could it be the type of sending unit I put in? I thought that all a temp gauge does is reads resistance? I disconnected from the sending unit again and checked the gauge and it seemed to be working fine?

Anyone have any idea's? I'm beyond my mechanic skills now! :mad:

[OUI]

Sounds like your thermostat is stuck in the open position. Cheap and easy to replace.

[DAFF]

I agree on the T stat theory... Makes perfect sence.

[CornRickey]

So when you way "moving off 100" do you mean its on 100 regardless of the boat running or not or do you mean it goes up to 100 from 0 when running but doesn't go past ?

[tadsell23]

I went to the local Mastercraft dealership and they also said it sounds like the T-stat has stuck open so I will try changing it out this weekend and I'll let you know if it works. Thanks for the input! The gauge goes from 100* to 210* and it doesn't seem to move at all....

[tadsell23]

Well,

I changed the T-stat this weekend and still the same thing? The gauge will not read more than 100*? I turned off engine once and it climbed up to 135* but as soon as I started boat the gauge went back to 100*? I have grounded gauge and it spikes out every time, changed sending unit and t-stat and the boat gauge will not read more than 100*? The gauge starts off bottomed out then climbs to 100* and stops? I guess its a bad gauge? Anyone have any other ideas?

[tadsell23]

Anyone have any idea as to what I need to do other than take the boat to the dealership and wait two weeks?

I have changed the sending unit, 160* t-stat and re-grounded the gauge to the ground block on the boat...All things recommend to do by Supra dealership. I can pull off the wire on the sending unit and ground the wire and the gauge will spike...But when I take the boat out on the water the gauge will go from 0-100* and stop, but once you turn off motor with key on the gauge will climb to 135*.

[Jetlink]

You checked the ground, what about continuity through the lead wire? Is it possible the guage is bad? Not too familiar with these new boats though so take that with a grain of salt.

[tadsell23]

I ran and new ground wire to the gauge this afternoon and still the same problem? I think it has to be a bad gauge but everyone has told me if the gauge spikes when you pull the wire off the sending unit and ground it out that the gauge is good? I have done that and the gauge spikes out? I don't understand why the gauge will go from 0-100* while running but won't go any higher until you turn the motor off then it will climb to 135*? As soon as you start the boat the gauge will go back to 100*

[Jetlink]

Sounds like either a gauge issue to me, either with the gauge itself or like I said the lead and not the ground going to the gauge as you said you replaced the ground.

[tadsell23]

Well, after just about replacing everything...Sending unit, T-stat, re-grounding gauge and still having Temp gauge problems. I knew it had to be the gauge. So, I called Dallas Ski Boats and dropped off the boat with them to put a new gauge in the boat. About 10mins after I left they called and said the sending unit that I was sold by another dealership was the wrong Ohm sending unit...So, they replaced the sending unit with the correct one and it works perfect! So, to answer many peoples question...Don't go to auto zone, or just go buy a sending unit at the local boat dealership that says " A sending unit for a 5.7 will work on any boat" IT WON'T....Thanks again Dallas Ski Boats and everyone else that tried to guide me through this problem.