DF140 Overheating

[TXFishin]

I have twin 2003 DF140's. In preparation for spring, and to avoid issues, I have performed the following maintenance.

New fuel filters from tank to engines

New Fuel lines from the tank back to the engine

New Primer bulbs (the heavy duty Yamaha bulbs)

Serviced and cleaned the IAC valve and set the idle per service manual

New zinc's including the rectifier zinc's

Fresh oil change, engine and gear case

Fresh fuel with Startron added

New water pumps/seals

New Thermostats

New spark plugs

The other day I was running at around 4000 rpm, both engines running like a sewing machine, all the sudden the check engine light and rev light with an alarm shows up on the starboard engine, it sags and looses power, I throttle back to idle, turn off the engine and it restarts fine.

This occurred 4 times in a 2 hour period, in-between it ran perfect as always, the temperature gauge never showed any signs of over heating, tale-tail was strong, and each time I would shut the engine off and restart and it would run fine again.

From what the gauges and alarm tell me, it looks like an overheat, but didn't seem hot, and from what I understand there are two conditions that would cause this, #1 cylinder or exhaust reaching maximum temp #2 the temp to rise time

I realize the temperature gauge it self may be slow to respond, but even after restarting the temperature was within normal range and didn't appear to be overheated.

I assume that since I am not getting any self diagnostic codes that all the sensors are working properly

I am not so sure that the source of the problem was an actual overheat situation

At this point I am wondering if I might have a sticky pressure relief valve triggering the temperature/rise alarm or a loose/corroded wire or something?

With all the maintenance that has been done on the engines, from what I could find on-line, I have already eliminated some potential causes.

This even happened once on the water hose, I made sure the water flow was good and the flushing cups were attached, it occurred within 15 minutes of starting the engine, turned off the engine and restarted and ran fine for the rest of the flush out

Has anyone had this sort of issue, or know what might be going on?

Any help or ideas on this issue would be greatly appreciated

Thanks!

[keakar]

try this:

drop the lower unit and pull the thermostat, then backflush from the thermostat opening and see if you see white powder or flakes coming out. if you do then you have a buildup of corrosion in the block that could be blocking the water passages in the heads. you might be able to flush most of it out this way if its not too bad but i doubt it.

if the problem continues the short answer is to pull the heads and check/clean out the water passageways since even the best cared for engines will still have buildup in them after 9 years.

now the bad news is as we all know, its never just as easy as unbolting and replacing head gaskets because (at least for me) you always seam to have a bolt somewhere that wont come out and you snap it off and have to fight with that PITA.

the internal temps can go up quickly and can take a minute or two to reach the outer surface of the block so it could indeed be overheating or maybe just a hot spot that not getting water to it. i think you are right to be unsure since you havent confirmed anything gets hot yet but im not shocked a motor that old is having cooling issues if the heads were never removed and cleaned out.

[Egorena]

DF140 Getting Hot

Good morning. I've got my DF140/2003 on the table right now. Found a tremendous amout of corrosion breaking loose and clogging up the #4 cylinder water jacket. Never got hot, but this hot spot was causing water leakage into the engine holder. Well, that is my theory. Engine has always run like a clock.

[TXFishin]

I really appreciate all the advice and ideas on helping to resolve this issue.

I didn't think about the engine possibly being salted because past advice / experience has shown that a salted outboard slowly runs hotter and hotter, and is consistent, where as this issue appears to be random, sometimes it will run for months without issues then start acting up again, however this is not to say that there could be debris floating around that periodically cause water flow issues, but both engines are running identical temps, and it doesn't seem to run consistently hot, slowly getting hotter and hotter as time goes on like I have seen in the past with salted engines

Also, when changing out the thermostats and the other maintenance work such as replacing the zinc's on the rectifier which allows you to view into the water passages I did not see any unusual build up

I will definitely back flush it though since I am going to removing the lower unit to double check the water pump and the water pump housing seal around the pick up tube

[TXFishin]

Good morning. I've got my DF140/2003 on the table right now. Found a tremendous amout of corrosion breaking loose and clogging up the #4 cylinder water jacket. Never got hot, but this hot spot was causing water leakage into the engine holder. Well, that is my theory. Engine has always run like a clock.

What was the resolution or fix for this issue? Remove the head and clean the water passages?

[keakar]

I really appreciate all the advice and ideas on helping to resolve this issue.

I didn't think about the engine possibly being salted because past advice / experience has shown that a salted outboard slowly runs hotter and hotter, and is consistent, where as this issue appears to be random, sometimes it will run for months without issues then start acting up again, ...

to offer an opinion on that, its like a salt shaker, its full of stuff but the holes only get blocked occassionally at random, this is what i think you were seeing. there are spots in and around the heads that are 1/4" or less space so even if they are 2-3" wide its still only 1/4" across

the minute you shut off the engine the water pressure drops and the "collection" of debris settles out, when you restart the engine itss flowing to a narrow spot where it jams up again and when enough blockage is there things start getting hot internally long before the outside since most sensors and guages read the water passage. if the water isnt getting overheated then the surface of the engine might not overheat either because the water is bypassing the hotspot and not picking up that heat.

not saying for certain thats whats happening but i hope that clarifies what "might" be going on

What was the resolution or fix for this issue? Remove the head and clean the water passages?

that would be my recommendation for both motors since they are 2003 models and when you do it be aware you will find there is a plug to block the water passage on each side of each head to direct water to flow completely around the whole head and not bypass any areas. look in the service manual and you will see it in the pictures (on mine it looks like a rubber hose stuck in it) i would clean around it as best as you can but not try to remove or mess with that plug if you can avoid it

[TXFishin]

to offer an opinion on that, its like a salt shaker, its full of stuff but the holes only get blocked occassionally at random, this is what i think you were seeing. there are spots in and around the heads that are 1/4" or less space so even if they are 2-3" wide its still only 1/4" across

the minute you shut off the engine the water pressure drops and the "collection" of debris settles out, when you restart the engine itss flowing to a narrow spot where it jams up again and when enough blockage is there things start getting hot internally long before the outside since most sensors and guages read the water passage. if the water isnt getting overheated then the surface of the engine might not overheat either because the water is bypassing the hotspot and not picking up that heat.

not saying for certain thats whats happening but i hope that clarifies what "might" be going on


that would be my recommendation for both motors since they are 2003 models and when you do it be aware you will find there is a plug to block the water passage on each side of each head to direct water to flow completely around the whole head and not bypass any areas. look in the service manual and you will see it in the pictures (on mine it looks like a rubber hose stuck in it) i would clean around it as best as you can but not try to remove or mess with that plug if you can avoid it

One thing that leads to me think that it may not be a salt issue is when replacing the thermostats and the two rectifier zinc's I was able to get a good look at the enside of the larger water passages and they looked to be in pretty good shape. This is not to say there is no issues in the smaller passages though?

I am definitely going to investigate this more to rule out all possible issues

[keakar]

well i'd be lying if i said i remembered exactly how the water flow works but IIRC the thermostat controls the waterflow for the headsand cylinder passages and the block waterflow is a direct unrestricted flow straight through which is why it gets less "salt" buildup then the heads and cylinder water jackets. also the larger passages allow any growth to easily be washed away.

most of the engines i found with buildup in the heads had little to no buildup in the main block passages.

your service manual should show a diagram of how the water cooling system flows

[TXFishin]

well i'd be lying if i said i remembered exactly how the water flow works but IIRC the thermostat controls the waterflow for the headsand cylinder passages and the block waterflow is a direct unrestricted flow straight through which is why it gets less "salt" buildup then the heads and cylinder water jackets. also the larger passages allow any growth to easily be washed away.

most of the engines i found with buildup in the heads had little to no buildup in the main block passages.

your service manual should show a diagram of how the water cooling system flows

Sounds logical for sure. The only thing that is confusing is why it would be an intermittent issue? I have been around engines that were salted up, and from what I seen is that they tend to run hotter and hotter over time, and when it gets to the point of overheating you would have to sit and let it cool down before it would start back up, but when this occurs all I do is turn the engine off and right back on and I am under way again.

I guess there still is a possibility that a "flake" or other debris have broken loose in one of the larger cavities floating around that could every now and then plug one of the smaller passages.

I even heard on a different engine that the rubber grommet on the top of the water pump housing was leaking, allowing the water pump to suck air around it causing it to overheat, but then again I would think something like this would be pretty consistent

[keakar]

I guess there still is a possibility that a "flake" or other debris have broken loose in one of the larger cavities floating around that could every now and then plug one of the smaller passages.

what im thinking is its a handfull of flakes that are like a brillo pad that arent able to pass thru the engine and leave and sometimes they are stacked so water can pass and sometimes the are restricting too much water flow

[TXFishin]

what im thinking is its a handfull of flakes that are like a brillo pad that arent able to pass thru the engine and leave and sometimes they are stacked so water can pass and sometimes the are restricting too much water flow

I am going to try what you mentioned, removing the lower unto and back flushing from the thermostat and see what it looks like

When you do this, do you seal the hose around the thermostat opening or just let gravity pull the water down?

I have also heard about people using lime-away, CLR, or Vinegar but I am not so sure that would do a lot of good, and from what I read it might make it worse if it dislodges more build up that i am unable to flush out

[keakar]

i did a little of both, i used a nozzle to give some blasts to it to knock things loose and i held the hose there and i also put the thermostat housing back in place and connected the hose to it that way i could use full pressure and volume to flush it.

i also went the other way a few times by hooking the hose to the water tube for the waterpump and got a lot of trash to come out both ways. every motor is different but just keep going untill you dont see anything coming out after a while.

when i finished i plugged the water tube and filled the block up with the used motor oil from my truck and let it sit overnight so the oil could neutralize any surface corrosion in there. flush the motor once more after to get most of the oil out and it will kill some grass but you dont want to let that loose in the water at the boat launch.

its not envoronmentally friendly and your first trip in water you will still leave a sheen everywhere but its the only way i know of to slow the corrosion down and neutralize it best you can short of taking the motor down.

[TXFishin]

i did a little of both, i used a nozzle to give some blasts to it to knock things loose and i held the hose there and i also put the thermostat housing back in place and connected the hose to it that way i could use full pressure and volume to flush it.

i also went the other way a few times by hooking the hose to the water tube for the waterpump and got a lot of trash to come out both ways. every motor is different but just keep going untill you dont see anything coming out after a while.

when i finished i plugged the water tube and filled the block up with the used motor oil from my truck and let it sit overnight so the oil could neutralize any surface corrosion in there. flush the motor once more after to get most of the oil out and it will kill some grass but you dont want to let that loose in the water at the boat launch.

its not envoronmentally friendly and your first trip in water you will still leave a sheen everywhere but its the only way i know of to slow the corrosion down and neutralize it best you can short of taking the motor down.

What about using a product like salt-away or something from the top down?

[keakar]

havent tried it yet but anything that will penetrate and neutralize the corrosion should be fine, i often tend to give things twice the time they recommend for things like that unless they are corrosive themselves

corrosion is very acidic (like battery acid) so besides removing and cleaning it you must find a way to stop the corosion by neutralizing the acid contained in the porous surface of the metal

[TXFishin]

havent tried it yet but anything that will penetrate and neutralize the corrosion should be fine, i often tend to give things twice the time they recommend for things like that unless they are corrosive themselves

corrosion is very acidic (like battery acid) so besides removing and cleaning it you must find a way to stop the corosion by neutralizing the acid contained in the porous surface of the metal

At least it will only help to clean out.

The other culprits I can think of that would cause a instant temp alarm might be an electrical issue, faulty sensor, the po-pit valve, or the water pick-up tube is leaking around the pump hosing causing the pump to pull air around the tube causing the the impeller to cavitate, which could be compounded if the pop-it valve doesn't regulate the pressure properly.

What ever it is I think it is being triggered, or thinking it is being triggered, by the Temp. rise vs Time rather than a full overheat situation, otherwise if it was a full overheat from general lack of cooling, either from being salted, lean on fuel, or poor water circulation, then it would still be hot after turning it off and then right back on, and might explain why the engine temperature never rises enough to detect it on the temperature gauges, the Temp. rise vs Time kicks in before it has a chance to get too hot