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]

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]

Originally Posted by Egorena

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]

Originally Posted by 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, ...

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

Originally Posted by TXFishin

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]

Originally Posted by keakar

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]

Originally Posted by 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

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]

Originally Posted by TXFishin

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