1996 DT150s BASS random Overheat Alarm

[Delta Bass Fool]

I have a '96 DT 150 BASS engine on my Bass Boat and like many others here I have very similar problems w/a continuing Gremlin that throw me random over heat issue alarms w/the Temp sensor and Rev Limit lit up w/the buzzer Tones.

So far I have done as several here have suggested in other threads and my problem seems to be one of those that will require a little more digging on my part and hopefully a little help from all you great people here.

The following is a list of all the things I have tried todate.

1) New Water Pump.
2) Cleaned and checked T-Stats
3) Trimmed the Starboard side of my intake cowling just above the Temp Sensor on that side of the motor to prevent it from pushing on the wires to that sensor.
4) Just recently adjusted the Idle so that it idles at about 800+/-50. This was done after the water pump install and fabrication to the inner side of the intake channel under the Cowling.
5) Purchased a 15 PSI Suzi Meter to install when I get more time to get back to completing the planned upgrades.

I have not been able to figure out if it has a water PSI relieve Valve and if so where it is located so I can inspect to clean or replace as needed.

I purchased the Service Manual from Browns Point item number 99500-87D08-01E and so far I can not seem to find any specific details about the '96 DT 150S BASS.

I am by no means rich otherwise I would take it to a shop. However I am prety good w/my hands W/I have to be and am quite capable of learing things while doing my own repairs.

Any ideas or thoughts on what to check?

I just purchased a '94 DT150S supplimental Service manual on ebay This morning April 8, 2019. I'm hoping it will have something in it. I'll see in a few days when it arrives.

Edit:

Just found some info incase I need to use the links in this following thread related to cylinder head repair work.

https://forums.iboats.com/threads/unrepairable-suzuki-dt150-hp-2-stroke.671063/

[booter]

So from looking at this from Figure 3, it could a few things: https://www.brownspoint.com/store/pc...%20(87-97).pdf

1: I'd check the heat temp sensor
2: Water block sensor
3: I'd check the flow of your cooling system from the pickup, through the water pump, and through the block. What's nice about the DT series, you can remove the cooling hoses and see if you are getting water through the block or not.
4: check your grounds and make sure that they are not corroded. Sometimes bad electrical grounds can cause sensors and stuff to read funny.

[Delta Bass Fool]

Thank you booter. So how do I go about unplugging the hose. From the top of the head at the T stat or the bottom of the Head? I want to avoid making a big water mess under the cowling where critical electrical components are. All the grounds look good.

Edit: I'm looking for a map or chart of the water flow from the pick up to the exhaust in the service manual I have. I don't recall seeing one but I was never looking for one either.

[booter]

Thank you booter. So how do I go about unplugging the hose. From the top of the head at the T stat or the bottom of the Head?

I thought that the hoses were attached via a hose clamp or something similar used on today's radiator hoses. If nothing else, maybe try back flushing it from removing the hose at the pee hole and feel for the flow of water.

[Delta Bass Fool]

Yes there are 4 hose clamps, a set of two per cyl bank. Two at the top where the T stats are and two at the bottom. I am not sure which way the water flows, from bottom up or top down.

[booter]

From looking at the diagram in the manual (page 8), it should flow from top to bottom and into the thermostats.

[Delta Bass Fool]

From looking at the diagram in the manual (page 8), it should flow from top to bottom and into the thermostats.

Not sure what manual you are looking at. My manual has a specification sheet on page 8

[booter]

Not sure what manual you are looking at. My manual has a specification sheet on page 8

This one right here: https://www.brownspoint.com/store/pc...%20(87-97).pdf

[Delta Bass Fool]

I just found this diagram in my manual on page 27.

Sorry I took a break for lunch and a shower. Would have been back to reply sooner otherwise.

20190408_115146.jpg Suzuki DT150S water cooling passages.jpg

[Delta Bass Fool]

It looks like the water comes out of the T-stat housing and down the hose and back into the bottom of the engine before it exits back out of the engine to the surface water. So with that in mind I'll remove the hose from the bottom so I can place them outside the cowling area to check for flow with out spraying water all over the back of the engine.

Edit: Now if only I had some clear hose for this I could do it with out taking the hose off and instead just look to see how the water flows.

[Delta Bass Fool]

I have been brain storming for the last week trying to learn as much as possible about my specific '96 engine. DT150S is what in on the engine better known as DT 150 BASS. Also referred to in the service manual as DT150STC. Then a third reference lists it as DT150STCLT for the Suzuki Parts Look up. So with 3 different naming schemes for the same exact year/model you can see how I was confused when it came to finding information pertaining to my specific engine. I did not think my Service manual covered my engine but once I put all the different pieces of the puzzle together and figured out all the different engine designations were all for my engine I realized the last section in my Service manual with the "W" ('98) has all the test procedures for my engine even though my specific BASS engine was only made from 93-97 as far as I know. Oh and I found out another interesting fact. It Looks like my engine is suppose to rev up all the way until 6500 RPM as that is when it should throw a REV LIMIT code.

Now armed with the correct info I got my lazer pointed hand held gun style infrared thermometer out and put a new 9 volt in it for testing purposes. It also has a spot for a K style Thermal Couple that I will use in the water for testing temps as well as taping to the block for testing cylinder temps. I'm going to get all technical and try to follow a game plan here.

#1 pull T stats and use the suspended in pot of water and measure the water temperature to see at what temperature they start to open and what temperature they are fully open.

#2 Do the same as #1 for both Cylinder temp sensors while measuring the Ohms at specified temperature ranges.
The resistance check for the cylinder temp sensors is as follows.
Water Temp F 32 / 77 / 122 / 135
Resistance 5.3-6.6 / 1.8-2.3 / 0.73-0.96 / 0.33-0.45

#3 Replace Water Pump and inspect for worn water supply bushings etc.

#4 Check Cylinder temperatures with Thermal Couple while engine is running.

I just purchased on ebay what I'm hoping is new and not a defective Monitor Gauge. Suzuki no longer sells these So at $59.00 I am a bit skeptical but the seller offers a 1 year warranty for this Monitor Gauge. Worse case scenario I return it if it's defective and look for another one until I find a good one. I left my boat outside in the weather for the last 2 years and now the Rev Limit light is not working so I don't know what exact code I am getting. The only thing that happens now is the Temp Light stays on when the Buzzer sounds. The Rev Limit light use to work before I left it parked outside. Heck now the trim gauge don't even work. The RPM gauge was not working at first until I revved the engine in the higher RPM range.

I'm getting closer to getting to the bottom of this.

Edit: It looks like the Monitor will throw a temp alarm if up to 7 minutes after starting the Starboard side reaches 100C and Port side Reaches 120C. Then 7 minutes after starting it will throw a code at 83C Starboard side and 120C Port side. This comes right out of the manual. It don't sound right but it's in the manual so I'm thinking this may be why it does not sound the alarm right away after shutting it off and starting it back up right away. After restarting the engine the Starboard side has a higher range before it sets the alarm off for the first 7 minutes.

[booter]

Glad you are starting to figure it out. Hopefully it's something simple such as your monitor gauge.

[Delta Bass Fool]

I hope so, thank you booster. It will be nice to finally be able to troll for stripers and idle around using the hummingbird 997 wide si/di :) w/o worrying about overheating.

I just hope I don’t have to pull the heads for cleaning of the water jackets.

[Delta Bass Fool]

Do ya'll think it will make a difference if I skimp on the pump and get this after market one on ebay? https://www.ebay.com/itm/Water-Pump-...4383.l4275.c10

[booter]

I think that you'll be fine as long as the parts numbers cross reference.

[Delta Bass Fool]

Thank you booster, I think I’ll just go with factory parts since I am chasing an overheat alarm. I pulled the T-stats and suspended them in a pot of water and discovered that they start opening at about 132F and are completely open by 136F. So I don’t know if that means I should change them or not. They are suppose to start opening between 118-126F so about 6F off. I used both a digital gun with the Thermal couple and candy thermometer simultaneously and there was only about a 1-2F variance between the two. I also pulled both heat sensors. The starboard side philips screw was being very stubborn so I cutout two flats using a dremel so I could get a good grip on that screw with some vise grips. After I got a good grip with the vice grips it came right out pretty easy.

Two of the T-stat bolts were stubborn as well. One more so than the other. I had to work it back and forth about 1/8” -3/16” of a turn back and forth practically the whole way out. The bolt does have some corrosion on it too. Any suggestions on the best way to clean the threads in the head before I put the T-stats back in?

Oh yeah I almost forgot, both sensors have some kind of stuff on them. The service manual states not to use any oil on the sensor or down in the hole the sensors are housed in. The port side sensor has some kind of runny looking oil while the Starboard side has some white goop. I’m not sure what it is, could be white lithium or some kind of thermal compound IDK.

I took pictures but they are on my phone and I’m in bed already on the iPad making my rounds before I crash for the night.

[booter]

To clean your bolts for your thermostats, I would use WD40 or something similar and use some anti seize on the bolts when reinstalling. While you have your thermostats out, I would flush out the cooling passages just to ensure that there is no debris or anything else in the passages.

For the heat sensors, I would see how much a new set would cost and just replace them and see what the goop is and make sure that's all new as well. Maybe the one got hot and explains why it's more runny compared to the other sensor.


Does the service manual say what temperature you would get a high temp alarm? I would still think that your stats are fine, but sometimes you never know and would think that they would be fully open once the motor is warmed up.

[Delta Bass Fool]

From start up to the first 7 minutes of warm up the Starboard side will set an alarm at 212F. After 7 minutes from starting at 183F Starboard side will set off the alarm and on the port side 248F will set off am alarm at any time during operation. So at least now I know the T-stats should not be the cause of the alarm.

[Delta Bass Fool]

For the sensors it is about $70 for the port side and $50 for the Starboard side. And about $45 per T-stat. I am wanting to pull the heads just for total reassurance that the cooling passages in the cylinders are not blocked and to inspect the 4 anodes under the heads. Gaskets are about $20 each but I am more concerned with not being able to remove the head bolts. I read some people saying Suzuki is famous for snapping bolts in the heads and lower units. I did loosen the lower unit bolts to make sure they will come out because I can't recall if I used water proof grease back in 2011 when I last did the water pump. I don't know if the heads have ever been off. I am going to lean towards not considering how clean the engine was when I got it. All the paint was super clean on all the bolts and block, no scuffs or chips from wrenching.

Oh yeah I also noticed a pinched wire to the Starboard side sensor under the coil packs as well as an electrical taped wire coming from the ICU or something like that.

[booter]

You should be able to test your cooling passages without taking your heads off. I would hook a hose up to where the cooling hose goes into the block and ensure that water comes out the thermostat housing. If you are not getting water flow through them, then I'd take the heads off to clean out the passages. If you haven't replaced your water pump since 2011, it definitely needs replaced as well.