DT-4 outboard water pump

[Daveinet]

Purchased a new to me boat last year. Being new to outboards, I never knew there was supposed to be water coming out the hole out the bottom of the engine. I used the boat all last season, and no water ever came out the hole. So, I've now learned that hole exists, and one should see water coming out of it. I can't believe the engine lasted all season without any cooling. I never ran the engine wide open, and usually less than ten minutes at a time. Somehow it survived. Last week, I pulled apart the pump, expecting to find a damaged impeller, however the impeller is in perfect condition. I have blow air through the whole system, and air flows out the little hole, as well as down the vertical shaft. Put the whole thing back together and yet no water flows out the hole. I popped the rubber cover off, where the shifter access hole is. As soon as I did this, I could see water coming out he bleed hole. Basically what was happening is that as soon as there was any kind of back pressure against the exhaust, it would prevent the pump from pumping. Exhaust was actually coming out the bleed hole at the bottom of the engine. I looked at the pump and found there is a tiny hole that sprays water on the shaft. There was water coming out that hole, but no water pumping up the tube. I removed the lower unit again, and ran it with my drill. A small amount of water pushed up through the hole that connects to the tube, but as I put my thumb over the hole, there was no real pressure, and all the water flowed out the tiny hole that sprays on the shaft. Not knowing what else to do, I plugged the hole with JB weld, as well as plugged the hole that is drilled between the outlet and the pump housing. (Looks like it is some bleed back hole to drain the water out of the engine) Any way, plugged both holes, and now I could feel pressure with my thumb. Put the engine back together, and now have water flowing out the hole on the bottom of the engine like it is supposed to.

So, while it works, it all seems very strange. The holes I plugged are all original factory drilled holes. I have no idea why they are there, or how this was originally designed to work. Does anyone know? Does anyone have a DT-4, and know about these holes? Or do these holes not exist in other units?

 

[woodster]

take some pics of what you are talking about so we can answer you questions plz and post them here

 

[Daveinet]

The pump is back together and the holes are plugged with JB weld, so it would probably not show up well in pics. I did a real quick drawing (sorry MSPaint). What is shown in red are where the holes are. The vertical tube has a rubber insert, shown in grey. the lower red hole feeds from the vertical tube back into the pump. The other hole just sprays water horizontal at the center shaft (shaft not shown)

 

[Chief RA]

No matter the type of outboard, all of them need the rubber impeller replaced every couple of years. Its likely yours is not sealing the rubber blades to the pump walls and not pumping because the rubber has hardened Get a new rubber impeller and put it in and redrill those holes out as they are pressure relief holes and should be open. That should do it. Chief

 

[Daveinet]

The impeller inside looked new, but I also replaced the impeller anyway, but it still would not overcome the exhaust pressure and pump water without plugging the holes.

 

[Chief RA]

I am not familiar with your motor model. Who makes it? I have never seen an outboard that the exhaust does not freely exit just above the prop. Chief

 

[kloudie1]

Suzuki DT-4, right?
Dave it sounds like you may have too much side clearance on top/below the impeller.. Maybe a gasket out of position? Gasket # 15 must be below part 16

Make sure the water seals are good.. Parts # 6 and 18 in attached link.. http://www.brownspoint.com/store/pc/BP_AP_AssemblyDetail.asp?ID=6540

Make sure you have the correct impeller.. my link may not be for your engine..

 

[Chief RA]

Claude: Sounds likely your suggestion of upper/lower impeller sealing as a problem likely is the answer since he says he has a new impeller. As we both know the exhaust is not the problem nor the holes he must reopen.
Chief

 

[Daveinet]

Yes, the drawing is correct, but of course does not show the holes that are in mine. When I inspected the impeller, the top and bottom does seal OK on the vanes of the pump.

Yes, I realize the exhaust is a symptom, not the source of the problem. As soon as the exhaust is under water, the back pressure is greater than the pump pressure, so it pushes the water backwards until the exhaust actually comes out the bleed hole. But there is some unknown issue as to why that happens.

 

[Chief RA]

You bet, because the exhaust should not be affecting the water pressure. Lots of the prints and parts layout do not show the pressure relief holes. Chief