DT150 possible false overheat alarm

[CAustin]

Hi. New member here. I have a 2002 DT150 EFI on a 2002 Sea Chaser that I just purchased. Took it on our first outing and after about a minute or two on a plane, I get a constant alarm that stops when I back the boat down to idle. About a minute later, I can get back on a plane but the problem repeats until I back off, or the computer does it. It also does this on a fast idle. On the muffs with the waterhose, no alarm.

Now, the water indicator temp stays the same regardless and has a good stream. I have checked the impeller and plate ( both look brand new ), as well as both thermostats which look new also. The heads look pretty good inside behind the thermostat housings. I have tested both temp sensors(two wire type) with an ohm meter and hot to boiling water. I dont have specs for what range they are supposed to be but, there was no variance between the two during the test. I have also checked the pressure relief valve (broke two bolts in the process and had to pull the powerhead to fix, will be drilled/tapped tomorrow ) and it looked fine with very little corrosion.

I have read that on these motors, the thermostats at one time were changed to higher temp thermostats and that the change was close to that of the temp to set the overheat alarm off. I have also read of a factory resistor that plugs inline with the temp sensors to correct the false overheat problem. My question is. Is anyone familiar with this if it is true or had any other experience with this? I am going to test the thermostats to tonight to see what temperature they open up at but thats about all I can do for now until I get the powerhead back on.

Also. Please correct me if I'm wrong but are there two separate alarms for cooling and oil? It's my understanding that overheat is constant and oil is intermittent. Any help would be greatly appreciated.

[CAustin]

Ok. Thermostats tested. Both start opening at 118-120f(about 48c) and not fully opening until 125-130f(about 52c) provided my thermometer is correct. Both are stamped 42c which equates to 107.6 f. Either my thermometer is a little off or they open slightly off from the 42c(107.6f), which I doubt they are going to be exact and a little off. I did test the thermometer however, with boiling water and it was pretty close to 212f.

Is anyone knowledgeable as to about what temp these overheat alarms are set at? Help would be extremely appreciated.

[seaox230c]

yes to both...the newer thermostats are a higher temp rating than the stock original...there is also an issue with false overheat and corresponding rev limit light and downtrim. I believe the fix is a resistor..do a search on this site for overheat warnings and you should see your issue. . My 225 does the same thing on occasion. A quick turn of the key to off and back to start fixes it so I know its an electrical issue because a true overheat wouldn't go away in 1/10 second

[CAustin]

I searched this website by each page and by using the search option, but couldn't really turn anything up. I also called a local Suzuki outboard dealer and they stated that they wasn't familiar with the resistor situation. Then again they also stated that they only really deal with four strokes.

I found a thread somewhere about someone in a similar situation, with a 225 and asking where to find a resistor in between a certain range but it seemed a lot higher compared to what my temp sensors range at. My temp sensors drop to mid 30 ohms when placed in boiling water and rise to low 100's when placed under cool water.

When you turn your ignition off and back on, is it instant while the throttle is still up or do you drop to idle then cut off? How long does it last throughout your trip without going off again?

[seaox230c]

I am pretty sure I found all my info about the overheat here on this site..I will try to find. I bring the engine back to idle..the overheat alarm still beeps..I turn off and on in less than a second and I'm good for 10 min or for the rest of the day and sometimes several trips...its very intermittant

[JUST-IN-TIME]

you have a poppet valve and also a water pressure sensor

[CAustin]

you have a poppet valve and also a water pressure sensor

Checked the poppit valve. Had very little corrosion where the spring seats in the cover. I seriously doubt it was enough to stick it.

On the water pressure sensor. Do you know its location? I have really only noticed the two temp sensors on top of each cylinder bank.

[JUST-IN-TIME]

well if you cleaned the poppet, which is under the head
and the head has no corrsion
then it is either a clogg in the cooling jackets or a bad water pump housing

i would run without t-stats and see if it over heats
if it does its the water pump

but if your running lean, you will over heat also

the earlier models had water pressure sensors

[CAustin]

Hmmm. It went away at least for now. I got the powerhead back on last weekend and took the boat out yesterday. No alarms went off the whole day. I guess I either "accidentally" fixed it during the powerhead removal and reassembly by maybe hooking up a wire that wasn't connected completely or something. Now I have an oil leak coming from either the oil pump seal or pressure side hose to tend with. Fun.