2015 DF15 overheating issue

[MasterSchwag]

I have a 2015 15hp suzuki outboard and it seems to have an overheating issue. Ive researched this topic a whole lot, and so far Ive only replaced the impeller < which was needed bad. Ive ordered the thermostat and will replace it as well when I get it. Before replacing the impeller overheating was an intermittent problem and would happen at any given time while moving (not idle). And yes the pee hole always spit water to some degree maybe just not full speed. After replacing the impeller the overheating was more of a steady problem happening less often but was reproducible by just keeping on the throttle for a minute or so. After a minute or so of cruising the red light comes on and the motor starts chugging and barely running (like a fail safe kicked in). I assume it thinks its overheating still but the pee hole water never gets hot! The motor has low hours on it and runs awesome until that red light comes on.

At this point, it doesnt sound like the thermostat is stuck but it seems like maybe a temperature sensor is bad? Can anyone point me in the right direction?

[Murray]

When you replaced the impeller did you replace the entire water pump assembly or just the impeller?

https://www.boats.net/catalog/suzuki...001/water-pump

Item 19. The link is from 2014, no listing for 15hp in 2015. The reason I asked about the kit is that sometimes the under panel(part #4)will warp causing inefficient water circulation. The water from the pee hole exits before it enters the block, basically the pee hole is an indication the the impeller is spinning. On my engine I have two temperature sensors (2009 DF90A), Cylinder Temperature Sensor, beside the thermostat and an Exhaust Manifold Temperature Sensor, in the exhaust manifold.

https://www.boats.net/catalog/suzuki...ch-df15ath-p03

Part #1 is one temperature sensor, no indication of a second temperature sensor so maybe your engine only has one temperature sensor. I’m not familiar with your engine so I really can’t help you there. Hopefully someone with more knowledge on the smaller hp engines will chime in.

[MasterSchwag]

When you replaced the impeller did you replace the entire water pump assembly or just the impeller?

https://www.boats.net/catalog/suzuki...001/water-pump

Item 19. The link is from 2014, no listing for 15hp in 2015. The reason I asked about the kit is that sometimes the under panel(part #4)will warp causing inefficient water circulation. The water from the pee hole exits before it enters the block, basically the pee hole is an indication the the impeller is spinning. On my engine I have two temperature sensors (2009 DF90A), Cylinder Temperature Sensor, beside the thermostat and an Exhaust Manifold Temperature Sensor, in the exhaust manifold.

https://www.boats.net/catalog/suzuki...ch-df15ath-p03

Part #1 is one temperature sensor, no indication of a second temperature sensor so maybe your engine only has one temperature sensor. I’m not familiar with your engine so I really can’t help you there. Hopefully someone with more knowledge on the smaller hp engines will chime in.

Yes sir I installed the whole impeller kit with the gaskets. The old one was warped and not working well I believe but the gaskets looked like brand new! Installing this kit made a huge difference but now the problem is still happening just more predictable. Im sure at this point its the temp sensor and this engine should only have one but Ive no idea where it would be lol. Any diagram or guide to finding its location?

[Murray]

Temperature Sensor, beside the thermostat and an Exhaust Manifold Temperature Sensor, in the exhaust manifold. If you only have one then I would GUESS it would be near the thermostat

[2014DF25ARS]

I had cooling problems with my DF25A engine. Mine would overheat if I let it idle for more than a few minutes. When I revved it or got underway, it would cool down and run fine. I found the tips on one or two of the blades on my impeller were broken off. This left me concerned that the missing pieces might be stuck somewhere in the cooling channels, so I removed the thermostat and blew compressed air down the channel toward the impeller. I convinced myself the path was not obstructed. After replacing the impeller and housing, I haven't had any more problems for the past 2 years. Did you see any damage to your impeller? And parts missing?

In my case, the pump wasn't working well and would not provide sufficient water flow when the impeller was spinning slowly. In your case, it sounds as though the water pump can't provide enough flow to remove the heat generated by the engine at high speed. I agree with you - it could be the sensor. But that seems unlikely to me. If I were in your shoes, I would remove the thermostat and make sure it's working OK. You probably know the process: put the thermostat in a pot of water with a thermometer, and heat the water until you see the thermostat open.

FYI, there are two types of heat failures which will cause the motor to go into "limp mode" to avoid damage. The error will trigger if:

(1) The motor gets too hot, i.e. above a certain temperature, or
(2) The motor temp increases at too high a rate, i.e. too fast.

Of course, you would also see this type of problem if your motor is mounted too high on the transom, such that it can't pull water when the hull is on plane. It's not ventilating, is it?

[MasterSchwag]

I had cooling problems with my DF25A engine. Mine would overheat if I let it idle for more than a few minutes. When I revved it or got underway, it would cool down and run fine. I found the tips on one or two of the blades on my impeller were broken off. This left me concerned that the missing pieces might be stuck somewhere in the cooling channels, so I removed the thermostat and blew compressed air down the channel toward the impeller. I convinced myself the path was not obstructed. After replacing the impeller and housing, I haven't had any more problems for the past 2 years. Did you see any damage to your impeller? And parts missing?

In my case, the pump wasn't working well and would not provide sufficient water flow when the impeller was spinning slowly. In your case, it sounds as though the water pump can't provide enough flow to remove the heat generated by the engine at high speed. I agree with you - it could be the sensor. But that seems unlikely to me. If I were in your shoes, I would remove the thermostat and make sure it's working OK. You probably know the process: put the thermostat in a pot of water with a thermometer, and heat the water until you see the thermostat open.

FYI, there are two types of heat failures which will cause the motor to go into "limp mode" to avoid damage. The error will trigger if:

(1) The motor gets too hot, i.e. above a certain temperature, or
(2) The motor temp increases at too high a rate, i.e. too fast.

Of course, you would also see this type of problem if your motor is mounted too high on the transom, such that it can't pull water when the hull is on plane. It's not ventilating, is it?

The impeller was just warped but the seals and inside the pump was mint condition! And its 1 and 3/4 inch too low at the moment so I think its not ventilating?

Ive installed a new impeller and temperature sensor from the factory, and it runs longer before overheating but still kicks in safe mode. I havent installed the thermostat yet but will tonight if possible. Water is coming from the peehole perfectly IMO and never does the water get hot to the touch. So im starting to wander if the thermostat is the problem?

[Murray]

The water from the pee hole is only to determine if the impeller is turning, at least with my engine. The water exits out the pee hole before it goes through the block.

[MasterSchwag]

The water from the pee hole is only to determine if the impeller is turning, at least with my engine. The water exits out the pee hole before it goes through the block.

Ok so Ive replaced the impeller, temperature sensor and the thermostat now and will take it out tomorrow to see what the final results are.

I noticed when I took out the old thermostat this is what it looked like inside. If water is flowing through here why is it mucky?
If there is a clog somewhere, where would it be? I know the motor has been dragged through the dirt for some time!

SmartSelect_20200229-223427_Gallery.jpg

[Murray]

The picture is a little blurry, what is that? Mud and lake bottom? Your first post you stated low hours so I assumed corrosion shouldn’t be an issue. Is this a salt water engine?

[MasterSchwag]

The picture is a little blurry, what is that? Mud and lake bottom? Your first post you stated low hours so I assumed corrosion shouldn’t be an issue. Is this a salt water engine?

Forgive me for being ignorant, this is the first motor I couldnt afford to take to a mechanic! Yes this is a saltwater motor and after removing the thermostat I now suspect the motor spent a lot of its life dragging ass through the mud. Im not sure what it is in the pic but it looked nasty. The motor looked to be in immaculate condition all the way around so I had no reason to suspect anything wrong! It does have low hours because Ive seen the maintenance receipts since it was purchased. I believe I bought the boat some time after the 20 hour service was done. Its had a gradient overheat since the first time I tested it but knew I may need to do some more maintenance.

The elderly lady I bought the boat from lived on a 1/2 mile long shallow canal leading to the indian river. The boat never had a trailer, so it always traveled through the shallow canal. (When I say shallow I mean six inches to a foot deep). To add insult to injury the motor also hung 3 inches below the keel of the boat so it was dragging really bad in the shallows.

[Murray]

Once you get that crap cleaned out I would suspect your overheating issues are solved. Is that gunk soft or get soft with the application of water? Reason I’m asking if soft then it should flush out the water jackets if solid then you might want to consider a vinegar flush.

[MasterSchwag]

Once you get that crap cleaned out I would suspect your overheating issues are solved. Is that gunk soft or get soft with the application of water? Reason I’m asking if soft then it should flush out the water jackets if solid then you might want to consider a vinegar flush.

It was muddy feeling. How do I even begin flushing out the motor lol?

[Murray]

Clean out what you can with your hands. Run it in a barrel or on muffs and collect the exhaust water just to see how much crap comes out. Scratch the idea of running it in a barrel, makes no sense running muddy water through a new impeller and thermostat. Keep the old thermostat probably nothing wrong with it. You really don’t need to see how much crap is in there it’s one of those “be interesting to know” The real test will be on the water.

[MasterSchwag]

Clean out what you can with your hands. Run it in a barrel or on muffs and collect the exhaust water just to see how much crap comes out. Scratch the idea of running it in a barrel, makes no sense running muddy water through a new impeller and thermostat. Keep the old thermostat probably nothing wrong with it. You really don’t need to see how much crap is in there it’s one of those “be interesting to know” The real test will be on the water.

So I should run salt away thru the ear muffs and cross my fingers that it makes it through the engine? If water isnt going through my engine but its peeing how do I know its clearing up the clog? If the motor is in the water and peeing strong how can we know anything is blocked?

[Murray]

Not sure how you would run salt away through muffs, that’s more of a barrel thing. I’d take it out on the water and see if your overheating problems are solved. The bulk of the sludge should backup at the thermostat and you’ve got that cleared. You could run salt away won’t hurt, your call. Concerning “the clog” you might have gotten it all at the thermostat, there might not be anymore issues, you won’t know until you try to reproduce the overheating issue.