Bad Thermosensor = Intermittent overheat

[CrankyGypsy]

the YDS is in transit.

i just got done taking a look at the three water jacket holes at the exit of the main exhaust pipe. they were all completely clear. i even put a long/skinny screwdriver in each one and tried scraping the inside of the jackets, but it kind of felt like i was scraping bare aluminum and i didn't bring much gunk out with it. i'm hesitant to try running it with the waterbox off to see the flow on the hose with it still inside the boat - anyone done that yet?

 

[OperationROL]

What is the pressure control valve?

Pictures taken from post from other site mentioned above:

 

[buckbuck]

Hmmm..ok, I thought that was for tempering the cooling water before it went in the block. Thanks bro.

 

[buckbuck]

Cranky, you could do that to prove that you have flow but the hose won't put as much pressure on the system as running on the water at 8000 rpm. Make sure you clamp off the cooling line between the intake screen and the Y fitting to maximize flow while on the hose.

 

[CrankyGypsy]

note: the High Output MR-1 does not have a PRESSURE CONTROL VALVE
(it's an easy way to tell if you are truly buying an HO model and not a clone)

 

[Cobra Jet Steering LLC]

Have you used a non contact thermometer to take readings of various points on the engine like the exhaust manifold and water box when the overheat warning comes on. Compare the readings from both engines to see if you are actually overheating and if so where .

 

[CrankyGypsy]

the YDS arrived and i did a quick scan on both engines:
it's showing that all available sensors are NORMAL. i say "available" because there are more physical sensors/switches on the engine than there are listing in the YDS. should i assume that they are lumped together -OR- are those sensors/switches not linked to the software?

@Cobra Jet Steering LLC yeah, i'm going to run up to the store and buy one of those today.

 

[CrankyGypsy]

took some baseline (idle/no wake) readings on several surfaces with an IR Thermometer (General Tools IRT207) while on the garden hose.

"CYLINDERS" refers to the individual manifold outlets approximately 0.50" from the head mating surface. "MANIFOLD" refers to the starboard crease where the manifolds from cylinder #1 and cylinder #4 meet, almost 0.50" above the COLLECTOR mating surface. "HEAD" temperature was taken on the horizontal side of the cylinder head, behind the engine hoisting tab and more towards the starboard side of the engine.
i tried to keep the device perpendicular and consistently about 1.5-3" from the surface for each reading. i let the engines run at least 5 mins at each RPM before taking readings and i clamped off the pump's inlet at the y-fittings while on the hose.

 

[CrankyGypsy]

the port engine is the side that has been overheating:


the starboard engine was intermittently overheating last year. since replacing the manifold and crankcase thermoswitch, it has not been an issue:


my only concern at the moment is with the HEAD temps on the engine that is not overheating - even at idle it is 12*F hotter than the problematic engine in No Wake Mode. i took several readings here, and at one point, the starboard motor was at 200*F in No Wake Mode. oddly, the problematic port engine seems to cool more efficiently in every area.

i also ran the motor without the COUPLER between the MAIN EXHAUST and the WATERBOX to check the water flow there. I bought 2" PVC pipe with a coupler fitting. I cut about 8" of pipe and slid it into the MAIN EXHAUST then used the PVC coupler to enlarge the PVC into the WATERBOX INLET joint. i was getting good (or what i perceive as good) flow from all three holes in No Wake Mode. (temp tests were done with everything connected properly).

the next tests will be running it out on the lake.

 

[buckbuck]

Attached are some numbers I had on my engines. Also attached is the latest YDS down load when I put it to bed this past season.
I think you are going to find that your temps will come up while underway and when you drop to idle they continue to climb because there is not enough flow to remove the heat. Somewhere you have a restriction.
Is this a California boat? Does it have catalytic convertors?

 

[CrankyGypsy]

@buckbuck thanks for the files. I was thinking last night, that I need to take readings on more than the exhaust, like you did. it is not a California model (no catalytic converters).

I'm hoping to get on the lake tomorrow, but the weather just turned to windy and chilly (15mph at 61°F) for the next few days. if the lake is choppy, I may just stay tied at the wind-protected dock to at least compare the pump cooling to the hose cooling.

 

[Cobra Jet Steering LLC]

You really won't get a good reading using the hose and idling, after you do a good hard run on the water you will get a better idea of what is going on.
If you notice one of your engines getting louder as you run it I have found that loudness is directly related to the level of water in the muffler, lower water louder sound from the exhaust. I still believe you have a issue with a heat sensor, I played around for months dealing with a bad sensor. Sometimes it would put the alarm on and kick into limp mode sometimes it just set off the alarm. I thought some of my pin connectors may be wet or corroded etc so I cleaned everything and sprayed silicon on the connectors before plugging them back in.
I learned not to spray water directly on the engine or any wiring connectors. What I do is cover the engines with spray white lithium grease, this has been very good for salt water use/ I have over 265 hours on both of my 2014 fx ho cruisers with no issues from electrical problems or corrosion, the only other thing I always do is add zinc to the ride plates . As for rinsing the engines I use car wash soap inside the engine via the flush kit prior to turning on the water, when the soap stops coming out the exhaust I stop rinsing. If I ever get water inside the hull I do rinse under the engine but I never spray water on top of it.
My supercharged Yamaha s h o had the issue with the sensor at between 500 and 600 hours, that sensor was behind the intercooler, but I believe most Yamaha sensor issues are the ones on the water box. As for your m r 1 engines check with @fairpilot I recall he had quite a corrosion issue with his in the exhaust manifold area. However if I recall correctly he ended up with water in his oil.

 

[OperationROL]

note: the High Output MR-1 does not have a PRESSURE CONTROL VALVE
(it's an easy way to tell if you are truly buying an HO model and not a clone)

Thanks for the info. One less thing to check.

 

[CrankyGypsy]

i think i found the problem

@Cobra Jet Steering LLC - you were right, again. seems to be the Engine Thermosensor.

at Lake Tarpon, FL today (air temp 64*F, water temp 68*F):
i ran the boat at idle and No Wake for about 10-15mins at the dock, taking temps on the exhaust and anywhere i could get a good reading on the engine itself. both engines were reading similarly on the IR Thermometer to what i was getting in the driveway (the starboard was again running about 10*F more in each area, except it was about 20* higher on that one head area). then i ran both engines at WOT. the boat ran great - i was actually starting to worry the chilly day was going to keep it within normal limits. the port engine finally tripped the water temp light on the dash but did not limit me to 3000RPMs. it just sounded boggy and lacked power. again, everything was about the same temperature: 10*F warmer on the starboard engine; 25-30*F warmer on the starboard engine at that one area of the head only(!!!). it cooled and i did it again with the same results. the results were so what i expected that i didn't even bother to write them down.

then i hooked up the laptop/YDS and ran it until it threw the error again: this time, the live Engine Temp Sensor in the YDS turned from the normal blue to an orange with a reading above the 266*F threshold ...maybe 268*F or something. letting it cool for a few minutes to drop below 266*F at idle, i did this a couple times with the same results. then i ran the same test on the starboard engine. it was holding steady at 145-155*F at the Engine Temp Sensor. all IR readings between the engines were what i expected/normal. obviously, running the engines at a lower RPM following WOT (rather than shutting them down) helps remove a lot of heat. also, it seems that running the boat with the throttles in the forward detent helps cool the engines much faster than the "Neutral" - probably because you're flushing the exhaust water well away from the intake.

with it likely narrowed down to the Engine Thermosensor, i started unplugging them on both engines while idling to monitor the YDS temps for differences. the port (problematic) engine's sensor was erratic - once plugged back in, it would bounce around the reading it had before the unplug and usually settle on a few degrees higher/lower of that reading. the starboard engine's sensor would very quickly settle into the reading it had without bouncing around it. and again, there was a 100*F difference between the two in the YDS. since i was alone, the one test i wanted to run but couldn't was watching the YDS while at WOT to find at what temp the port sensor would just go haywire. in any case, i'm fairly certain this is the issue. i even ran it the length of the lake (how long it took to overheat each time; about 5miles) with the Thermosensor unplugged - it was throwing the Port Engine idiot light (3 blinks), but ran beautifully. on the GPS, it was running 46-48mph against the wind and 50mph with it (winds: NNW 15mph). once near the dock, i plugged it back in so i could use the No Wake mode - no lights/errors.

i think if i remove the two water hoses on the case near the engine anode, i should be able to get a wrench on the sensor to remove it.

 

[Cobra Jet Steering LLC]

Sounds like you have the issue , but you were out there today! I'm in Pinellas county also and I stayed home haaa. too cold for me to be on the water today.

 

[buckbuck]

Good job Cranky. I hope you find that to be an easy fix.

 

[CrankyGypsy]

yeah, it was cold - i hid behind the windshield while underway.
the water looked rougher from the dock than it actually was, and it was about 4degrees warmer than the air temp.

thanks, buckbuck. i was able to finagle a miracle getting the crankcase thermoswitch out/in of the starboard's engine last year with the exhaust still on. compared to that, this thermosensor should be cake.

 

[CrankyGypsy]

i replaced the thermosensor today with a used one. since it's an HO, i was able to pull the two water hoses under the manifold between piston #4 & #3 for access to the sensor - otherwise, the Pressure Control Valve might need removed by non-HO owners. then i was able to blindly get a 17mm open box wrench onto the sensor and break it free, swap in the new one, snug it up, and re-attach the hoses. done. water test next week.

the old one was definitely not looking good:

when i did the manifold replacements, i noticed the rubber that fills/protects the back of the sensor had broken out (i actually thought this particular sensor was on the other engine). i cleaned it really well and then sealed it with a few coats of Corroseal - a rust converter that i requested a free sample of. i had hoped it would convert the rust and seal any new water out. well, obviously that stuff did not do a very good job at all.

 

[Cobra Jet Steering LLC]

geeee who would have ever guessed? LOL

I bet you have a bad heat sensor I had the same problem and learned it is a common issue, had it fixed under warranty and no more issues.

 

[buckbuck]

That has got to make you feel good that you definitely found your problem.