SAN GT40 Running COLD???

Hope you can help with this one...I'm sure it's less of a mystery than I'm making it out to be.

Since I bought my 2002 SAN GT40 in October, it has run at ~140* and not any higher, according to my temp gauge. Additionally, we've seen some small plumes of white steam coming from the exhaust, both while on the lake and in the driveway with the Flush-Pro attached. The exhaust has also smelled a little like gas, I've seen a slight sheen in the water, and the boat has idled a little rough, which to me means that it's running a bit rich.

After putting these all together and doing some more research, I decided to try swapping out the thermostat on the off-chance that the previous owner had replaced it with a 143* instead of the 160*. After popping off the housing, I discovered that the existing stat was in fact correct and looked to be functioning properly. I went ahead and replaced it anyway and ran the boat in the driveway for 20 minutes. It still did not get above 145*. I didn't see any steam and the gas smell decreased slightly, but it's not completely gone.

Does anyone have any idea what's going on? I've always read that normal operating temp for the GT40 EFI is 160* or so--is there a possibility my engine just runs a bit colder? I want to make sure that I'm not wasting gas and potentially causing damage to the engine by having it run this way.

Any help you can provide is appreciated...thanks!

The only thing I can think of is that maybe the temp sender for the gauge and the engine may be malfunctioning? If it is, its going to send incorrect information to the computer. Try replacing it. Those engines are suppose to run at 160*. The other thing you can check is that maybe the thermostat you bought is bad? I know its probably fine, but if the temp sender is not the problem, maybe the thermostat is stuck open, and if thats the case, the engine is going to have a hard time warming up.

Try replacing the temp sender. I'm pretty sure if the computer thinks its running cold, its going to send more fuel to the engine like as if the choke was on. Also, make sure you are getting correct voltage to everything. Just to make sure, check the alternator and make sure its putting out 14 volts when the boat is running. If the voltage is low it can mess with the computer and make the boat run funny.

Kyle, funny you mention that--I've also been having some alternator issues lately. I wonder if they could be related. I'll give those things a shot...thanks!

Yeah the boat needs 12 volts to run the computer properly. If the voltage drops it will make things act weird. My Malibu that i just put a TBI fuel injection system on, the alternator went out and it made my temp gauge read 140 and caused my tach to do weird things. Once I replaced the alternator everything was all good! Tach was solid and my temp gauge read 160. That may be your problem. I still would not rule out the temp sender though...

The tough part about getting the alternator checked is that none of the auto parts stores can do it if it's out of the boat. They say that if they can't look up the application/part number, they don't know the specs on it and their tester won't recognize it. SO, I have to figure out a way to squeeze the boat into the AutoZone parking lot and hook up the FlushPro to their hose bib so they can test it on the boat. Although, if they're just going to test voltage at the battery posts, that'll be a waste of time.

Yeah man just use a volt tester to do it. If its putting out 14 volts on the charge wire (usually orange) then the alternator is fine. You can even just test the voltage at the battery when the boat is running. If its anything below 14, then that alternator is probably going bad.

Well, took the alternator to an auto-electric shop that could test it, and it ran perfect. Just put it back into the boat, made sure the tension was good (1/4"-3/8" deflection) and started her up. Voltage at the battery before start was 12 even, voltage afterward was appx 13.7. So, looks like the alternator is ok. The boat is running in the driveway now to see if I can get it to heat up. If that doesn't work, next thing I'm going to look at is the temp sender.

Ran the boat for 20 mins and still won't go over 145*.