1996 DT150S Overheat buzzer and light problem at low speed and idle.

[Solarman]

Record temps on powerheads with thermal gun while you are flushing. Try to identify where the hottest areas are and read/record those temps.
Get the extra hoses off so the flushing goes throughout its normal paths. Write down temps. When too hot let solution cool, then run another cycle till hot, and keep checking / recording temps.

[N2 Fishing]

I’m finished flushing. Did it cold with engine off using an electric sump pump. It seems like it has helped and possibly fixed the overheating issue as far as I can tell. I say this because I’m still not comfortable running the enginewith how it is currently running. See remarks below.

The tell tell pee stream is very strong now and the engine stays cool enough to the touch that I can rest my hand on the top of the engine near the Thermostat housing.

HOWEVER:

There is a problem with the motor where once it reaches operating temps and the engine idles down. The engine is acting like it is freezing up and wanting to die. It pops and sounds like a major misfire. It scares me into thinking it is trying to lock up from poor lubrication.

I am running the engine off of a satellite fuel tank mixed with 50:1 fuel to oil ratio.

I pulled a hose that returns vapor/fuel from the bottom of the block and returns it to the VST. This hose is very spongie and slips right off of the nipple it connects to. I plan on replacing this hose and check valve associated in the return hose. This hose seems like it has been fuel soaked and caused it to become soft thick and spongie.

I made a video that shows how this nipple at the bottom of the engine is spitting out a lot of raw fuel. This does not not seem normal to me. Please take a look at this short video and give your best assertion as to if this is normal or not.

https://m.youtube.com/watch?v=yNNFIZ59Nxo&pp=sAQB

[N2 Fishing]

That fuel smelling fluid yhat was coming out of the Vent/lubrication nipple at the bottom of the power head that runs through a filter before dropping into the top of the VST had me concerned. So I pulled all the spark plugs and unplugged all the injectors to see if I could purge all that stuff out.

I cranked the engine over for about 10 seconds at a time letting it rest for a minute between cranking cycles.

I was able to get all that dirty looking liquid cleared out eventually and filled up 5 paper towels in the process.

Then I put it back together enough to start it and see how it would behave.

Initially after starting the engine It was doing a little chugging and popping or actung like it wanted to stop running and eventually it did die. So I primed the fuel primer bulb and started it back up.

I was doing this with the oil pump filling the VST and using the satellite fuel tank mixed at 50:1.

It started clearing up but was still acting a little odd but not as frequently and not as vilent or loud. I decided to record a video of it but then it decided to start running better so the video was of no use for diagnosis purposes as it had cleared up and started running better.

I let it run for about 5 min. Shut it down. Started it back up and let it run for 11 minutes. I could hold my hand on both cylinders and tge alarm never gave an over heat condition.

The tell tell pee streen is very strong and seems like it was most likely the cooling passages clogged up this whole time.

i still need to buy new fuel lines for the engine side on tge fuel pumps. The hoses I purchased are too thick.

while running it at idle for 11+ minutes I observed the port side get ss high as 160 degrees and the starboard side as high as anout 140 degrees on the too of the head where the temp sensors are located. Any place else like on the cylinder jugs or head on the lower cylinders read loser temps on both sides.

It'll be a minute before I can take this thing out for a tedt drive to see if the flush has solved the over heating issue.

To be continued:

[Solarman]

Will wait to hear the results.

Good luck. Post back on what it does.

[N2 Fishing]

Ok Update:

I took the boat out two days in a row, Saturday & Sunday. Tried to force an overheat alarm. I could not get the engine to overheat. This is very good for now and makes me very happy.

However even with new fuel lines and new Suzuki primer bulb, I am having to prime the fuel lines either during long idles or long drives through slow 5 MPR no wake zones or when engine is left off while fishing for an hour or two.

I’m thinking this may be related to one or both low PSI fuel pumps. If a pump has a small crack in a diaphragm or damaged check valve then is it safe to assume this could be causing the problem with loosing prime? Or should I be looking elsewhere.

What else could cause the fuel to drain back into the boat fuel tank?

[N2 Fishing]

I forgot to mention the engine was topping out at about 5700 RPM at WOT with no issues staying the course indefinitely. It seems the float tab in the VST is adjusted adequately.

[N2 Fishing]

I did have to replace the fuel strainer bowl rubber O-Ring a few years back when the engine first started having prime issues. Wondering If I should just replace the whole strainer bowl assembly to rule out any chances of air intrusion which may be leading to a syphoning type situation from an air leak in that fuel strainer bowl assembly.

[N2 Fishing]

Does anyone know how to test the tilt trim switch and gauge? I looked through the whole manual and was unsuccessful at finding anything.

[Solarman]

Sorry it's taking so long to respond, this site has been not responsive lately.
Not sure what you're trying to test. The tilt trim switch sends voltage to one wire for up, or to the other wire for down? And the guage...is it possible wires got disturbed behind guage/helm?

Good luck.