DT9.9 cooling problem

[Pettson]

Hello good folks.
I'm new here. ☺

I recently acquired a 1989 DT9.9 that starts and runs sweet as a bee.
Problem is we have no cooling. I've gone through the water pump, re-checked it seven times, thermostat, and flushed all the water lines. But still no go.
What else should I look for? running out of ideas now.

[Murray]

”I've gone through the water pump“ Does this mean you’ve replaced the entire water pump assembly with a new kit? The kit would contain new impeller, base plate, gasket and o ring.

[Pettson]

Yes. Replaced the whole kit. Even cleaned the gasket surfaces, and made triple sure the impeller was twisted in the right way?

[Pettson]

But wait now!
What O-ring?

[Pettson]

I got a Suzuki original spare parts kit. Had the impeller, gaskets and the little wedge thingy... But no O-rings?

[Murray]

On my engine (2009 DF90A) there is an odd shape o ring that fits in the pump housing ensuring a good seal to the base plate. If your kit didn’t come with one then you don’t need it. Your post #1 you state you are getting no cooling. What lead you to that conclusion? Overheat alarm, no telltale or a hotter than normal engine? Salt water engine?

[Pettson]

There's no telltale at all, only hot, dry exhaust fumes. Engine gets smokin' hot after only a minute or two.
I checked the thermostat, and even tried rinning the engine without it, but to no difference.

I don't know the engine's full history, but the previous owner used it in sweet water, as was I going to do.

It hasn't been used for a couple of years, but starts and runs sweetly, apart from the cooling issue.

[Murray]

When running the engine, are you in a barrel with enough water to completely submerge the entire water pump plus a couple of inches?

https://www.boats.net/catalog/suzuki...350/water-pump

Can you get a garden hose to part #10 and force water into the water tube while pulling hoses off trying to find where there might be a blockage? While running the hose try shoving a stiff weed wacker cord into the telltale hole seeing if you can dislodge any blockage. Try running the garden hose into one of the cooling hoses and see if water comes out the next cooling hose. Basically you need to determine where the blockage is if that’s your issue. Do you have a Suzuki genuine service manual for your engine? The manual will have a diagram for the cooling water path. Search vinegar on this forum, perhaps a soaking in a vinegar solution might help.

Hopefully someone more familiar with your engine will chime in with ideas.

[Solarman]

#1. Many owners don't understand that the impeller must be wet, to be lubricated (all motors). If the motor was ever started/turned over enough without water, the impeller can fragment, sending pieces of the rubber impeller up into the motor. If this possibly happened there might be some blockage causing a lack of flow of water to cool the motor.

#2. Another possiblity, is that exhaust pressure is preventing water being picked up by the water pump. This is usually caused by burned out grommets connecting the water pick up tube that supplies water to below the pump. Exhaust pressures blow through the burned out grommets pushing water back from getting to the pump, the pump can't get water and the engine gets hot.

#3. If the water supply tube from the water pump to the motor is, damaged, not connected properly, or the connecting grommets are damaged/not good, then the water being pumped up may not be getting up to the motor?

#4. This same exhaust "back pressure" can occur if there is a hole(s) in the exhaust plate on the side of the cylinders, but most of the time, you should still have some kind of tell tale output? This depends on where, and how big the hole(s) actually are?

Without knowing the actual history of the motor, I would remove the lower unit, inspect/change the grommets that supply water to the pump, as in #2 first; at the same time, I would put a sock/screen on the water tube that goes into the top of the water pump, then using a garden hose, with a rag around it put back pressure in the thermostat hole backwards (thermostat out) to see if anything was blocking the pathway from the pump, by checking what gets caught in the sock/screen attached to the water tube. If you have fair water pressure, you should also get water through the tell-tale?

Good luck, post back on what you find out.

[Pettson]

Thanks for the ideas.
I'll do some experimenting with the garden hose tomorrow. ☺

[suzukipr]

Hello, im working on a recent acquired DT4 motor. I found a overheating issue. After multiple multiple test in a barrel with a drill, I found the issue is air bubbles trapped inside the impeller. Previously I seal the exit water passages under the engine to divert all water to the tell tale hole and prevent the exhaust to push back the water, but that does not solve the issue. So I worked first to prevent as possible air entrance to the pump. I found two little drain holes under the leg, and are capable to send exhaust bubbles to the pump when running at high rpm. Then I be sure to seal the pump housing and the lower plate. If it leak exhaust in to the housing, its a problem again. Right now I decide to modify my pump housing, to pump the water from the top of the housing, I think is the best way to pump away all air bubbles all the time. I will let know if that works. Have a nice day.

[Murray]

Air bubbles? Are the air bubbles really exhaust gas bubbles? I’m not familiar with the DT4 cooling system but the exhaust exiting out the engine should have a separate passageway than the water intake system. Usually the water intake is at the front of the lower unit and mid section and the exhaust exits out the rear portion of the mid/lower through the prop.

[Solarman]

Suzukipr, start by using your own post. Give us details on your motor, then tell us your problems. Dont seal drain holes, or weep holes, dont seal pump plates, or anything like that. Exhaust getting into pump should not happen.

Start your own post, give us your motor info, stop sealing everything up!