Overheat issue solved

[BKirish]

hi all- been an owner of an AR240 going on our 7th season now and never posted but have used this forum extensively and it has literally saved me thousands. So I just want to say thank you to all.

Latest issue: had numerous intermittent port engine overheat advisories. Thought it to be debris, but it continued to get progressively worse yesterday on the water causing us to single engine it back to the dock.
Overheat again 30 min later, 2 min into flush. crap.... jet boater forum all evening looking into all the potential issues that could be the cause. Range of issue: simple-super complex. This am started with the simple stuff; Topping off battery charge now, switched spark plugs from Port/Stbd (new ones every season, and new set of 4 on order), pulled out the thermostats on both motors and one open, one closed (the one on the overheated motor closed.) I am hoping this is the dealio/culprit. thoughts?

I put one of these on order last night based on this site and my "strategy" this morning was 100% garnered from this site, thx again (assuming i have successfully identified the offender that is)

brian

 

[Julian]

Did you clean the intake screen?

 

[buckbuck]

@BKirish I hope that is the problem but unless that thermostat was hot when you noted it was closed, then it sounds like it was operating normally. We are here to help you if you need us.

 

[BKirish]

Did you clean the intake screen?

I did a visual inspection, appeared clean.

 

[BKirish]

@BKirish I hope that is the problem but unless that thermostat was hot when you noted it was closed, then it sounds like it was operating normally. We are here to help you if you need us.

So - yeah. Got excited, the bad thermostat is on the "good" motor. Was hoping they were both bad but after a hot water dunking I was back at square 1. Poop

 

[BKirish]

I could ID 3 sensors on each motor is that correct? Looks relatively easy to swap out sensors with good motor sensors to see if the problem lies within the sensors? Any advice to approach?

 

[Gym]

You could try running with the thermostats out to prove it one way or the other. No water leaks? How long from cold start to overheat?

 

[Jgorm]

The ecu will throw a code if the sensor is bad. You can view them with the yds to do a reality check. Does water come out the correct ports while in the hose? Does the same port feel hot in both engines?

 

[boudin]

Do you have water coming out the pissers at 6000 RPM+?

 

[buckbuck]

 

[buckbuck]

Above video is not your boat/ engine but similar

 

[BKirish]

Watched that video a dozen times. Nice work! Latest- swaped out the exhaust thermostat sensor with other motor and put in a new thermostat (prob not bad but ordered) On hose for 15 min all looked good, warm water coming out exhaust port- some residual waters coming out pump, water coming out thermostat port (terminology) and dropping out pee hole. Of note : water temp steady 81 degrees. Other motor: original good motor, no thermostat: other motor (original bad) teljermk sensor. Started, looked promising, all water ports doing their thing, watched as water temp crept up from 85 to 95 and shorty 1 min after got overheat. This motor had no issues unt I swapped thermostat sensors (and took out the actually bad thermostat) . New sensor on order. Learned a lot about the boat, thx for you folks and positive attitude!

 

[buckbuck]

Which port were you measuring?

 

[BKirish]

Do you have water coming out the pissers at 6000 RPM+?

Will check next time on hose - thx

 

[BKirish]

The ecu will throw a code if the sensor is bad. You can view them with the yds to do a reality check. Does water come out the correct ports while in the hose? Does the same port feel hot in both engines?

unfortunately the closest yamaha place is 1.5hrs away and i don't have access to a yds. I thought they were coming out the correct ports until... the "ports on both stbd and port exhaust nozzles (labeled exhaust pipe jacket in buckbuck's pic) appear to be intentionally filled with something. so there is definitely no water flowing from either motor from that port. all others appear/feel to be same/same.

 

[BKirish]

Which port were you measuring?

View attachment 76757

waterbox exhaust gas and T-Stat ports. The other port "exhaust pipe jacket" are both filled solid on each engine. definitely intentional.

 

[Jgorm]

What are they filled with?

 

[Sbrown]

What are they filled with?

Silicone like substance. It's normal.

Hate to tell you, but when you originally pulled the thermostats out, the one that was closed was the good one, the one that was open was probably the bad one. Without getting too complicated, too much water flow sometimes is as bad or worse than not enough water flow.

 

[Weeb]

Silicone like substance. It's normal.

Hate to tell you, but when you originally pulled the thermostats out, the one that was closed was the good one, the one that was open was probably the bad one. Without getting too complicated, too much water flow sometimes is as bad or worse than not enough water flow.

I agree a thermostat is normally closed and opens as the engine gets hotter. The silicone stuff freaked me out a little too lol just pull it out.

 

[buckbuck]

@Weeb I have been disconnected for awhile. If you are referring to the exhaust pipe jacket picture above having silicone in it - be careful!. I believe only the MR-1 engines had this. Your 1.8 liter engines do not have that and you may have opened a hole into your boat. Please double check by looking into that area by removing the hatch.