Severe corrosion on Suzuki 15hp

[Captain Bill]

Originally Posted by ranger42c

I've recently discovered the over-heating problem. We only have about 17 hours on the outboard, and it went into limp mode as I brought it from ramp to mother ship. The whole cylinder head was clogged with salt; the techs had to chip it out... huge $$$ to learn that...

Turns out part of the problem seems to be that running fresh water through the flushing port, engine off, apparently doesn't at all route fresh water up around the cylinder head. Gotta to that with the muffs, engine running, so the water pump circulates flush water everywhere.
<sigh>...

-Chris

Is this a Suzuki?

[a64pilot]

I run mine while flushing, I figure it must be getting water through the head, or it would overheat pretty quick?

[Captain Bill]

Originally Posted by a64pilot

I run mine while flushing, I figure it must be getting water through the head, or it would overheat pretty quick?

Are you using ear muffs or the flushing port. If I understand the flow path correctly the flushing port is above the water pump. I suppose some water might back flow into the pump but it could be a bit hard on the impeller. When mine first overheated it had been running for at least 10, maybe 15 minutes. I was above idle but at low speed in a no wake zone. I'm sure the thermostat had not opened because before I cleaned it it was still closed at 190f. If idling it might take quite a while for the thermostat to open.

[ranger58sb]

Originally Posted by Captain Bill

Is this a Suzuki?

Yes, DF15A.

Could well be about that thermostat thing; when the engine's not running, the thermostat isn't open... so maybe that inhibits full circulation of water being injected only through the flushing port.

Maybe.

-Chris

[Captain Bill]

Originally Posted by ranger42c

Yes, DF15A.

Could well be about that thermostat thing; when the engine's not running, the thermostat isn't open... so maybe that inhibits full circulation of water being injected only through the flushing port.

Maybe.

-Chris

I think they charged me $275 when the pros cleaned it out. I actually ran fresh water through the flush port for 2.5 hours and it still overheated before I took it to them. I don't think any water was getting through the head because the thermostat was closed. They said it was clogged with salt and they had to use acid to get it out. What kind they didn't say. I used Ospho diluted about 4-1 and Ospho is 44% phosphoric acid. It chewed up the salt/precipitate quite quickly. I sprayed it through the thermostat hole and through the Anode hole. I did it three times and loosened some of the bigger chunks with a pick. I then flushed it with water with the thermostat and anode covers off between sprays. A lot of crap came out of those holes. It took about two hours but most of that was waiting for the acid to work and cleaning the thermostat. I'm now carrying a spare thermostat. I sprayed about a pint of diluted Ospho into the engine. After I finished I took it for a nice run to make sure all of the acid was flushed out of the system. That beats paying $275. I don't know if this a unique problem associated with Suzukis or a generic problem with cruising outboards that don't get flushed with fresh water regularly. Salt Away is supposed to be used to clean salt out of your outboard according to the package, but I've never heard anybody say they had issues if they didn't use it. Suzuki advertises the motor as lean burn. From my pilot days I know a lean mixture burns a lot hotter than a rich mixture. Maybe Suzukis burn so lean that they run hotter than the critical temperature for raw water cooled engines.

[a64pilot]

I only flush it through the port. I made a short hose with plastic threads, cause I didn’t like threading my metal garden hose into the plastic engine ones, so my little hose makes it plastic to plastic.
Exhaust gas temps and engine water jacket temp don’t necessarily track, as long as there is enough cooling water flow.

Even with the thermostat closed, there should be bypass flow of water, not as much as when the thermostat is open, but some flow.

Bill, I’m going to go out on a limb and say you have a problem with your particular motor, and it’s not a design problem, or there should have been a whole bunch of overheating stories by now.
My guess is your thermostat is bad and sticking at times, a bad pump or something.

[ranger58sb]

Originally Posted by Captain Bill

I think they charged me $275 when the pros cleaned it out. I actually ran fresh water through the flush port for 2.5 hours and it still overheated before I took it to them. I don't think any water was getting through the head because the thermostat was closed. They said it was clogged with salt and they had to use acid to get it out. What kind they didn't say.

Our service guys had to dismantle some of the parts (that were in the way) and then chip the salt deposits out, a bit at a time. They had pics to illustrate, too, and it was way more than $275 <sigh>...

Partly because it took three different visits to finally get to the root of the over-heating problem, which wouldn't show up when they ran the motor in a barrel. Or even when they ran it with the dinghy in the water... but I think without a load. Running it in a barrel of Salt-Away for several hours -- what they usually use to flush -- didn't fix it. My guess is that it might have done, eventually, if it were being run hot enough for the thermostat to open and long enough to be effective.

Originally Posted by a64pilot

Even with the thermostat closed, there should be bypass flow of water, not as much as when the thermostat is open, but some flow.

Bill, I’m going to go out on a limb and say you have a problem with your particular motor, and it’s not a design problem, or there should have been a whole bunch of overheating stories by now.

Our service guy said that's not the case; raw water only gets to the head when the water pump is in action and the thermostat opens. OTOH, he's a (major local Suzuki) service guy, hard to know if that's really authoritative.

Still, I wouldn't have called any of this a design flaw. If what he said is true, the manual could be more explicit; I only used the flush port because I didn't see any reason -- stated in the manual -- to have to start the motor.

I think our own situation is exacerbated by non-use. Four years old and only 17 hours... Usage dropped dramatically after we lost our last Golden Receiver... and when we're docked at home, we're blocked in, can't launch the dinghy without moving the mother ship first...

-Chris

[Captain Bill]

Originally Posted by a64pilot

I only flush it through the port. I made a short hose with plastic threads, cause I didn’t like threading my metal garden hose into the plastic engine ones, so my little hose makes it plastic to plastic.
Exhaust gas temps and engine water jacket temp don’t necessarily track, as long as there is enough cooling water flow.

Even with the thermostat closed, there should be bypass flow of water, not as much as when the thermostat is open, but some flow.

Bill, I’m going to go out on a limb and say you have a problem with your particular motor, and it’s not a design problem, or there should have been a whole bunch of overheating stories by now.
My guess is your thermostat is bad and sticking at times, a bad pump or something.

You are assuming the bypass port is not clogged with precipitate, which it was. As I noted, both incidents occurred after the motor was sitting for a month. Ranger42, has a low use engine so maybe that has something to do with it. My first thought was the waterpump, so I changed it out before taking it to the pros. The blades had taken a set from sitting and may not have been pumping very well, but I think it would have taken more than 10-15 minutes of running at slow speed to clog the head with salt/precipitate. In any case more regular flushing is in my future, so we'll see if that makes a difference. I'm also going to make it a practice to change my internal anode every time I change my leg anode and that will give me a good idea of what kind of buildup I am getting, if any.