Suzuki 2011 DF150 Overheat issue

[jrozycki]

My last trip of the 2022 season I was idling around trying to find a spot to fish and the overheat alarm went off. I did what any reasonable fisherman would do and dropped anchor and fished for a few hours! When I pulled anchor and drove back to the docks the engine never over heated.

So this spring I:

• replaced the thermostat (old one was corroded with white crust) I'm in sound off SE CT / RI
• performed a complete water pump kit install

First trip out this spring it happened again putting out from marina in a no wake to open water. I realized if I throttled to a few hundred RMPs higher than I was running through the no wake the temp goes down. And cruising on plane the temp stays at 160.

So I pulled boat and:

• Dropped lower unit to double check the water pump install
• replaced the rubber bushing at the top of the water pump even though the old one seemed fine but thought it might have a little slop
• Back flushed the engine through the water return hose into the thermostat housing (with thermostat removed of course) and water flows out the water tube just fine (lower unit obviously was still removed)

With the lower unit still removed and the water return hose still disconnected from the lower part of the engine, I put a garden hose directly on the water tube and turned hose on full blast and water never came out the return hose. The water basically comes out of the driveshaft housing aft of the water tube. If I let the water run long enough it eventually pees but sort of weakly.

My main question: injecting water into bottom of the water tube, shouldn't water easily be be reaching the thermostat to where I'd see it exiting the water return hose?
And if it should, which it doesn't in my case, it sounds like I have an issue with my water tube or its connection with the powerhead.

Any thoughts?

 

[99yam40]

Not sure about your motor, but water out of the Tell tale does not come from/thru the stat on any outboard

 

[jrozycki]

Not sure about your motor, but water out of the Tell tale does not come from/thru the stat on any outboard

 

[jrozycki]

I agree. My manual shows the tell tale as a branch in the water flow before the thermostat.

 

[99yam40]

Running a piece of weedwacker line up the TT will open up the restriction.
or try blowing some compressed air up the tell tale while running on muffs or in a tub.

 

[jrozycki]

Running a piece of weedwacker line up the TT will open up the restriction.
or try blowing some compressed air up the tell tale while running on muffs or in a tub.

Thanks but perhaps my post was not clear. I'm overheating at idle. No water reaches the thermostat when i blast water straight into the water tube with the lower unit off. I'm thinking the connection at the upper water tube and bottom of cylinder block is leaking.

An engine can have a totally clogged TT tube and the engine could still be getting cooled water just fine. Water out of the TT is just an indicator that your pump is pumping. I've already ensured that the TT tube is not constricted, regardless.

The main question I'm trying to answer is why doesn't water reach the thermostat when i blast water up the water tube with a garden hose? I'm assuming a garden hose flows as much if not more water than the water pump could.

And i don't think the water tube is blocked as i can feed a stiff rod all the way up to the bottom of the cylinder block.

I've already back flushed engine with CRL through the return hose thinking i have blocked water passages within the cylinder block.

So my thought is that something is wrong with the seal at the top of the water tube and engine block.

Just looking for confirmation on that. Thanks!

 

[jrozycki]

Found my issue. I took off the oil pan water jacket and found a hole corroded through allowing water to leak back down into the lower unit

 

[jrozycki]

Found my issue. I took off the oil pan water jacket and found a hole corroded through allowing water to leak back down into the drive shaft housing.

 

[99yam40]

Wow, that is strange

 

[jrozycki]

Wow, that is strange

The tech at my marina said somewhat common for Suzuki's. They use JB weld to fix things like this, so that's how I fixed mine

Since it was a wide hole, I JB welded a piece of aluminum stock over the hole and then filleted the epoxy around the edges. Water pressurizes this space so this should work.

I know when I first found the hole, I wedged some rubber gloves over the hole and installed the cover to hold the gloves in place, and when i ran water from garden hose into the water tube, water came out the thermostat return hose as I was expecting.

This hole was basically depressurizing that water jacket and only under higher rpms did enough water make it into that jacket to pressurize it enough to force some water up to the cylinder heads to keep the engine from over heating, but not enough pressure to completely fill the heads and force water to exit through the return hose. Like I said full garden hose on water tube I never got any flow out the thermostat return hose. Might explain why at high rps it only cooled down to 170.

Under low rpms probably all of the water leaked through that hole causing temp to rise.

 

[palumanic]

Found my issue. I took off the oil pan water jacket and found a hole corroded through allowing water to leak back down into the drive shaft housing. View attachment 382473

oh, looks pretty bad

 

[FIN FEVER]

Great, now I have to procure a gasket and take mine apart to check just to see what mine looks like. Thanks for posting your findings.

 

[FIN FEVER]

While I was doing fluid changes on my 2010 DF150, I decided to pull my water jacket cover and was pleasantly surprised to see NO corrosion! StillI guess always flushing has paid off.

 

[Crispin]

I am chasing an overheat alarm but haven’t done my impeller yet. I did find this tho which is bad like the OP jrozycki… This water came squirting out when I trimmed up out of the water. Can someone speak to how bad this is? If it’s just a water jacket, I also was thinking JB Weld. I saw a gear case is $1500 and that’s before changing everything over.
There is a hole corroded through the case but I think it’s just through to a water jacket and not in to the actual gear case.
I’m a little disappointed in amount of corrosion. I’m boating in drinking water and the anodes are in pretty good shape. Should I change them anyway?