DF50, High Speed overheat alarm

[redaye]

For over nine months I've experienced an overheat alarm on my DF50 when I get above 4800 rpms. I've had in to my dealer 3 or 4 different times with this issue. We've replaced a lot of stuff. Here's the facts.
1.) engine is peeing fine, always has.
2.) replaced, water pump, thermostat, two sensors (exhaust and manifold)
3.) only occurs above 4800 rpms.
4.) temp alarm comes on and engine throttles down to idle. Temp alarm continues until I switch it off. Then back on. No alarm, and will run fine until I push it up to high rpms again.
Motor is an '05 and has 300 hrs on it. Kept in perfect condition. Serviced every year. Runs frequently but, I don't have to run far. Engine ran fine, high speed and otherwise until about 9 months ago.
Service guys don't seem to be able to trouble shoot this problem. I'm getting a little tired of replacing parts that don't need replacing. Love my Suzuki but, replacing good parts is getting old.

[Moonlighter]

When you replaced the water pump, did you do the full kit including the housing, or just the impeller?

If you didnt replace the housing, suggest you do that. A small imperfection in the housing that is not visible to the eye can be the cause of these kinds of issues.

[redaye]

Impeller and housing were replaced. New sensors, etc. Had it back to shop since your response. They removed the lower unit to observe cooling path all the way to the power head. All clear. Ran motor today. Still getting overheat alarm at over 4500 rpm. It looks like it's peeing good but, if you hold your finger over the port, it feels like it's pulsing. They want to pull the power head ? Does this sound reasonable to you? Motor has less than 300 hours. Need some direction here. I don't think this mechanic knows what he's doing. Just replacing parts.

[redlowrey]

Impeller and housing were replaced. New sensors, etc. Had it back to shop since your response. They removed the lower unit to observe cooling path all the way to the power head. All clear. Ran motor today. Still getting overheat alarm at over 4500 rpm. It looks like it's peeing good but, if you hold your finger over the port, it feels like it's pulsing. They want to pull the power head ? Does this sound reasonable to you? Motor has less than 300 hours. Need some direction here. I don't think this mechanic knows what he's doing. Just replacing parts.

.....You need to take a temp sensor gun out with you and when the temp alarm comes on take the cowl off and shoot a beam over your cyl head and exhaust manifold and check the temperatures. If the temps are high you won't have to do voltage drop tests on your wiring to the ecu from the temp sensor and exhaust manifold sensor. You might have a build up of salt in the holes in between your head and block and when going at high speed the restriction won't transfer heat away quick enough. In your post you say exhaust and manifold, the sensors are cyl head and manifold.

[Solarman]

You may have exhaust interfering with water flow? Do you have a strong pee stream, and good normal/ steady flow of water from exhaust port on back of motor when at those higher rpms? If flow spits and sputters when alarm goes off, you may have exhaust getting into water pathway somehow at those higher rpms?

I'm not as experienced with the 4 strokes, but this did occur on my 2 strokes.

Just a thought, good luck.

[Tides2]

Similiar problem on df50 - overheat occurs between 1000 and 3000 rpm - full throttle appears ok and temp lowers to about 60 c - just had head removed and cleaned at dealership but they stated that they could not get to all the waterways- problem still there - everything else checks out. - Mine is a 2007 motor and used in lake water only so i never flushed after use. - seemingly there was a lot of algae growth build up over time which may be theunderlying problem. - i am at the point of getting new motor -

[Moonlighter]

Have you tried a vinegar flush?

[wellcraft34]

I’d also check out the pressure valve, located on the port side down low under the midsection cowling. I’ve had those cause some strange overheat situations

[wellcraft34]

If the pressure valve is stuck closed you’ll get high speed overheat, stuck open low speed overheat

[Zijls006]

Hallo Redaye, is your problem solved? I having the same issue.

[Kunselmr]

Same problem as well. 2007 DF 40. Exhaust overheats. Cylinder head temperature is normal and flow appears normal. Had the motor torn down and passages cleared last year. It ran normal until now.