Both engines overheating

[Fred Durko]

I’m sure this topic has plenty of posts but I can’t seem to find but a few of them. I have a 2004 sx230 with the MR1 Engine.After about seven minutes in the water both engines overheat within 20 seconds of each other. I have flushed out both engines (Great video understanding the MR one cooling system )and have good water flow. I feel like it’s electrical maybe a bad sensor. Is there any common link between the two engines and the warning lights which cause it to go into limp mode.

 

[Jeremiah]

Have you tested the thermostat? I know it is unlikely that both are bad but definitely want to rule that out.

 

[Fred Durko]

Yes They’re working properly right now I’m running it without them.

 

[buckbuck]

This is highly unusual. There is probably an easy fix.
Did you happen to clamp the cooling lines coming from the jet pumps? I would suggest reinstalling t-stats as I feel they provide the back pressure required to fully pressurize the exhaust cooling. Keep us posted.

 

[Fred Durko]

The motors are not getting hot. They are running about 190 - 210 degrees. That’s why I was wondering if there is a common link between the two motors. The right Engines warning light will come on first than 20 seconds later left engine warning light comes on. I will shut the motors down and drift around start them up 15 minutes later all lights are off.

 

[boudin]

Are you getting water out the pissers? Pull each one off from the front of the exhaust, and blow compressed air through them.

-Greg

 

[buckbuck]

@Fred Durko Please take the time to watch this video.

You probably have 3 sensors that can report high temp. The analog one you reference is mounted on the engine block. The temps you mentioned are pretty typical operating temps. It would lead me to believe you are getting hi temp alarms from the exhaust sensors. Use an infrared gun to shoot various places on your engine. I have found the oil filter runs about the same temp as the engine at the analog sensor. The exhaust manifold has a spot where three holes dump the water into the exhaust stream. Those holes sometimes get plugged up, especially in salt water boats. Keep us posted.

 

[itsdgm]

I’m sure this topic has plenty of posts but I can’t seem to find but a few of them. I have a 2004 sx230 with the MR1 Engine.After about seven minutes in the water both engines overheat within 20 seconds of each other. I have flushed out both engines (Great video understanding the MR one cooling system )and have good water flow. I feel like it’s electrical maybe a bad sensor. Is there any common link between the two engines and the warning lights which cause it to go into limp mode.

Welcome, and sorry to hear about your issues.

As far as i know, there’s nothing in one engine that will report an alarm to the other engine. They have separate ecu’s, sensors, and alarm indicators. The only shared electrical is the battery.

Do you have any indication of cavitation/loss of thrust with the boat? Loss of thrust means loss of cooling water flow since the pump supplies cooling water to the engine.

Also, when’s the last time the spark plugs have been changed? Old/fouled spark plugs have thrown an overhead light on my boat before. It’s cheap and easy to eliminate plugs as the source of the issue.

Having it happen with both engines at nearly the same time is very unusual, unless there was a significant event in the past that affected both engines. It’s quite possible that there’s something blocking the cooling system somewhere. Possibly picked up at the same time. Have you checked the inlet filter screens? They’re located on the port side of each pump. Maybe they’re filled with sand or something.

 

[Beachbummer]

Since it's happening on both at the same time, I would not rule out sediment or debris deposited in some cooling passages/hose that is keeping the water away from some location in the engine. It's the one link between the 2 engines I can think off. Best of luck!

 

[CrankyGypsy]

@Fred Durko your description of the problem is extremely vague.
- "out on the water" - does that mean WOT?
- where are you (and previous owners) located - salt or non-salt?
- how long have you had this boat?
- "the motors are overheating...motors are not getting hot" - ok. is this via a laser gauge or YDS?
- does the overheat cause it to go into a definite "limp mode" (limited to 3000 RPMs) or does it just show the idiot light along with sounding louder with a loss of power?

there is no electrical link between the motors and there is no shared water way connecting the motors. the only thing they share is the air they bring through the intake and the water they bring in through their individual jets.

possible problems:
1) hoses kinked. odd they could both have a kinked hose, causing the same overheat threshold. it's hard to tell hooked to a garden hose. but if you clamp off the fresh water inlet from the jet where the garden hose adapter hose connects at the Y-fitting, you can get more pressure throughout the system for inspection.

2) bad thermosensors. again, odd they are both bad at the same time. best way to tell is to hook up the YDS and run WOT until it overheats. I did this alone, but a partner will help. monitor the rise of the Engine Temp in YDS - it should rise smoothly. if it jumps around, spikes, or acts erratic then the sensor is bad. most likely, it will work smoothly to a certain temp then suddenly spike up over 266*F and go into limp mode. it may also take a long time to settle back down compared to a properly functioning sensor - idling may not help, as you may need to shut down and wait 5-10mins. you should be able to replace the sensor under the exhaust manifold without taking anything apart.

https://jetboaters.net/threads/bad-thermosensor-intermittent-overheat.8032/page-2#post-139460

3) scale build-up. since they both overheat at about the same time, this would be my guess. this can kick on the overheat idiot light (around 250*F, i think), but may not cause a limp mode. instead, each motor could sound louder and feel like it has lost some power ...almost like cavitating. if it overheats due to scale, it may not take long to cool back down - simply idle around in the first detent for 1min. fixing this will require a closed-loop flush.

https://jetboaters.net/threads/closed-loop-flush-of-mr-1-with-marine-descaler.8443/

 

[Jgorm]

I'm with @Beachbummer that you clogged up the intake filters. That would explain this perfectly. As mentioned, nothing is shared between the engines except battery power.