Bad Thermosensor = Intermittent overheat

[CrankyGypsy]

solved: Post #34

i think i remember reading about someone fixing a re-occurring overheat issue, but can't recall the member ...or if it was even this site. if i remember correctly, the "fix" was flushing out a theorized build-up of crud for an extended period of time - i'm curious about the set-up, time, and if any chemicals were used? this is my first boat, but there seems to be quite a bit of crust built up in various places to me.

for some reason, @Ronnie @OperationROL @sysinu all pop into my head for possibilities, but i couldn't turn them up in my searches.


THE DETAILS:
my port engine has been temp faulting. throughout this season, it seemed to fault more often/earlier/easier. my prior outing was october on my way back to the dock after wakeboarding. i know it's not accurate, but feeling various areas, i could not tell one engine was running hotter than the other. out of frustration, i unplugged the thermo switch on the crankcase to avoid the limp mode and get it back to the trailer. it started up an ran fine in the driveway during the flush. i figured i'd mess with it over the winter.
well, my family is in town, so we took it out yesterday (81*F air temp with 72*F water temp). i kept it around 8ooorpms in hopes of preventing the overheat because that worked at the beginning of the season. this time the temp light came on, but it did not go into limp mode. ??? instead of preventing me from going over 3000rpms, it got very loud/boggy and felt like it was cavitating. i pulled some small grass from the cleanout, but it did not help. unplugging the crankcase thermo switch did not change anything either - i did not try unplugging the thermo switch on the exhaust. we anchored for a while and once it cooled, everything was fine again.
looking around today, i am seeing that the inlet on the port engine's water box is showing more "tarnish" than the box on the properly-running starboard engine. it has a layer of dusty/crusty residue on it - like it is evaporating water off it and leaving the minerals behind. so it may indeed be running hotter. my worry is there may be a gasket issue within the large rubber elbow of the exhaust instead of a build-up issue?

last season i had overheat issues with both engines during extended WOT, but the starboard engine has not had an issue this year. prior to the 2015 season, i had both engines out of the boat. at the time, they both got new exhaust manifolds, oil, plugs, air filters, thermostats, a drive-train alignment, and refurbished OEM impellers with new OEM housings. i was careful not to pinch any cooling lines and there are no leaks (brittle lines and rusty clamps were replaced). both pairs of pee-holes are clear/flowing equally.

i will be purchasing the YDS. i'm also going to install the 22mm Trail Tech Temp Sensors near both thermostats like cybuch has:

i want to rule out any false error codes and be able to see trends of the temps in real-time while noting the circumstances the YDS can't: determining if/what variables (RPM and straight vs slalom) increase the temp and which cool the engines better. i'd also like to know what temp trips the idiot light on the dash.

 

[Bruce]

Have you checked the cooling intake strainer?

I have only experienced overheating twice. Both times it was due to debris in the jet causing cavitation. I would take a very close look at that jet to see if anything could be in there.

It is possible that something was in the jet causing your cavitation and overheating yesterday then it washed out while you waited for the engine to cool.

 

[buckbuck]

Cranky, have you checked the cooling lines and the plastic fittings? The oil cooler fitting and the exhaust manifold both have substantial restrictions in them. The Y-fittings also may have plastic flash in them from the factory due to improper manufacturing.
A couple years ago OperationROL had some overheat issues that were resolved by flushing. This was during a Shelbyville trip.

 

[Cobra Jet Steering LLC]

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.

 

[CrankyGypsy]

thank you much, guys.
i'll check the strainer and fittings (i checked both Y-fittings when i pulled the engines, but didn't check any of the others that didn't need removed) while i wait on the Trail Tech sensors and YDS ...if it's a bad switch, they should find it.

one questions: will pump cavitation that is bad enough to cause an overheat allow for a solid/strong pee-hole stream? am i wrong thinking that it would cause some sputtering at the pee-hole if there's air in the system?

 

[Julian]

I would think that if you have cavitation caused overheat you would NOT have a strong pee flow (from both pee holes for that engine).

There was a post at one time about crusty thermostat causing an over heat (if I recall correctly)....flushing might clean the thermostat...I'd pull it off an visually inspect it.

If you have strong pee flow, I doubt your intake strainer is clogged....but it is easy to check and clean.

 

[txav8r]

Cavitation will definitely interrupt cooling water and thus your pee hole streams. You have two for each engine, one from the thermostat and one from the exhaust. If this has been an ongoing condition since engine removal, I would consider that your cooling line runs may have a restriction. And I would again check those fittings @buckbuck is talking about and look at his video, it is excellent detail of the cooling system, how it works, and what can restrict it. The video may give you some ideas of other areas to check in the system that you may not have thought about.

 

[itsdgm]

I'll throw out something from left field here. But our vintage engines were very sensitive to spark plug condition. I had an overheat issue that was resolved simply by changing the plugs. There weren't any classic signs of fouled plugs and they were less than one season/30 hours old.

Just something to think about. I hope you figure this out soon.

 

[Ronnie]

@CrankyGypsy , it wasn't my thread that you are thinking of but I do recall something very similar where the poster not only resolved his issue by flushing extensively with at hose, he also explained / outlined the entire cooling system of the mr1 (140 and/or 160 hp engines). It may have been buck bucks post and I think it was on the other site and was titled mr1 cooling system or something close to that.

Whenever I've had temp warnings on my 998 cc, 1,052 cc and now 1,812 cc Yamaha engines it was right after my impeller was fouled by floating vegetation. Once I cleared the debris, including any in / blocking the pump strainer the warning would go away.

Sorry I couldn't be more helpful. Good luck getting this resolved quickly and inexpensively.

 

[Scottintexas]

When you say you replaced the manifold did you also replace the exhaust pipe #12 on the picture below, if not do you remember checking it?
we have seen those cooling passages get clogged on salt water boats, douggotschalk did an extensive breakdown with pictures, his and the person he was helping were intermittent cooling problems, I can't seem to find it at the thread at moment to attach for reference,

 

[Scottintexas]

I still can't find the blocked cooling passages thread but here's a good read that popped up from a google search at YJB about a bad gasket blocking the passages,
http://yamahajetboaters.com/forum/viewtopic.php?f=1&t=40908&start=45

 

[Scottintexas]

douggottschalk pictures and explanation are on page 2 of the link above,

 

[CrankyGypsy]

i appreciate it guys.
i was very careful not to kink the cooling lines during re-install and i'm getting good flow out the pee-holes.
both thermostats are only one season old.

@itsdgm if it's as simple as a plug, that will be awesome.

@Scottintexas thanks for the link!!! i only replaced the manifolds (between the crankcase and the exhaust collector) because they were leaking and/or corroded ...didn't notice any build-up in them though. and i didn't want to open up the can of worms that was #12 (those gasket$ add up) - but looking at the pics in that link really quick, it doesn't seem as daunting as i had thought. it actually looks like it might be a possibility to pull that portion without engine removal: maybe just remove the airbox and then pull the cleanout tray to move the water box?
because of the mineral deposits i noticed on the water box inlet, i wouldn't be surprised if this turns out to be the problem area. actually, i noticed some discoloration/staining of the gelcoat near that engine's outside exhaust port at the jet - it scrubbed off, but it makes me think it was getting hotter exhaust fumes than usual
...the clues are all pointing to the douggottschalk posts on YJB.

CHECKLIST:
- disconnect/move water box and inspect the water jacket holes.
- replace the plugs, run YDS (rule out thermo switches), install the Trail Techs, then water test.
- consider extended flush on hose.
- pull the main exhaust pipe (i may end up pulling both to give them a thorough cleaning).

 

[CrankyGypsy]

just remembered: when i yanked the exhaust to pull the manifold on the starboard motor (the port is the one currently giving me problems), i had a bit of sand and tiny rocks dump out of the collector. i'll bet that stuff can make it back into the main pipes, combine with some salt crystallization, and clog them up like concrete.

 

[Ronnie]

Can you loosen the crud that may be I the hoses by hand or with compressed air or just try and flush it out with water?

 

[CrankyGypsy]

Can you loosen the crud that may be I the hoses by hand or with compressed air or just try and flush it out with water?

it's been an ongoing problem that seems to be gradually worsening. I'm definitely going to give it a go by starting with the least evasive options. I'll try popping hoses and flushing at different locations. but from what I've seen and what was in that link, it probably isn't going to budge without some scraping. I've been very good at flushing/cleaning, especially after salt water ...unfortunately, I've realized over the past two years that the previous two owners may not have been.

 

[Gym]

just remembered: when i yanked the exhaust to pull the manifold on the starboard motor (the port is the one currently giving me problems), i had a bit of sand and tiny rocks dump out of the collector. i'll bet that stuff can make it back into the main pipes, combine with some salt crystallization, and clog them up like concrete.

@CrankyGypsy Operating in the shallows can cause that. One of our members, possibly @Mud Skipper had a plugged cooling passage from ingested sand. Remember our intakes draw from 3 feet down at idle even though our draft is less than half that. With regard to flushing I have used CLR a couple of times as a preventative as I boat in the salt. You can also use vinigar.

 

[buckbuck]

is the video for cooling system. But you probably know more about it than I. You have a reputation for being very mechanical.
Going by memory, the 'overheat thermoswitch' will turn on at about 225 degrees F and stay on until it drops to about 190 degrees F. I have a YDS download where I got to 244 degrees (while trouble shooting my issue). Once I corrected the problem I could never get temps above 210.
Off topic, but could you take a look at the oil pressure input (oil pressure switch) once you have your boat at operating temp and YDS connected? At idle my boat always turns that 'on' according to the YDS but I never get a dash light. OperationROL's old boat did the same. I think it is just a characteristic of the MR-1 but am curious if yours does the same.

 

[OperationROL]

I did have an overheat issue that was resolved with a good flush. However, the overheat issue did return for the current owner. I have been trying to help him resolve the issue (intermittent). This thread provides great options to try. Seems like the pressure control valve, water-box gasket holes and the main exhaust pipe and the next logical steps.

 

[buckbuck]

What is the pressure control valve?