Siphon hose pumping water into boat

[jds12]

Hi all,

I recently replaced my sport jet drive (mercury 175 xr2 1997 sea rayder).

My siphon hose is actually pumping water into the boat, only while running. Can someone give me an idea why this might be happening.

Appreciate any help.

 

[Julian]

As I have no idea what a siphon hose would have to do with a jet pump set up....I am of zero use here!! Perhaps if you posted some pics, we might have a better idea of what you are up against?

 

[jds12]

It's supposed to siphon out any water that gets into the engine compartment while underway. It's actually hooked to the jet nozzle and the suction is supposed to pull any water out.

I just can't find any info on why it would be flowing in instead of out like it's designed to. It's only coming in when the engine is running.

Figured someone might have a better understanding of how it works.

Thanks

 

[Julian]

Obviously would work on some form of negative pressure in the pump. If the point where the intake is inside the pump is obstructed at all it may be causing positive pressure at that location and reversing the flow. Without a photo of the intake and where it is drawing from the best I can do is guess that something in the area of the point at which it is pulling water through to is clogged, or missing caulk or malformed in some way.

One option would be to simply plug it up and buy a bilge pump, hose and through hull fitting.

If you can get us some pics we might be able to spot something.....

 

[jds12]

Thanks Julian.

Here's the explanation that I found:


On the auto siphon hose up near the top there should be a little fitting that will have a tiny hole through it. If this hole gets plugged it will siphon in instead of out. Also, if there is something at the nozzle end that is wrong it can do this. Things like the pipe outlet partially blocked, if you have the vertical deflector in it they sometimes get bent or break free and cause turbulence in the nozzle that will affect your bilge siphon.

Apparently it's normally used on jet skis. I guess that the newer jet boats don't have this set up.

 

[Scottintexas]

We don't see to many Mercury drives on here, maybe @Bilmon or @Cobra Jet Steering LLC can help, they have some experience with the older types,

 

[Cobra Jet Steering LLC]

If it is only coming in through the pump siphon hoses when the engine is running I can only think of one reason, the o rings where the siphon tubes mount up to the pump housing are bad or totally missing . The tubes should be on the forcing cone behind the impeller , that part bolts to the main body of the pump, where the openings of the tubes mount against the pump body you must have a good seal or water from the pump will get forced into the siphon tubes and some of it will go back into the boat

 

[jds12]

Is it part #3 in this diagram?http://www.boats.net/parts/search/M...ial Number 0E203000 Thru 0E344999)/parts.html .

The fitting screws into the main jet pump body. Looks like it's sealed with thread sealer.

Also, could I just block off the siphon tube or will it mess something up by not being sealed correctly?

Appreciate the help

 

[jds12]

This is where the siphon tube enters the jet drive housing. Is it the fitting with the red sealer you're talking about? Thanks again.

 

[Cobra Jet Steering LLC]

That is actually different than what I was thinking your pump had, however the forcing cone where this tube ends up at the right on this picture should have a hollow tube that is inside the cone, as water is forced past the hollow metal tube it draws water from the boat so perhaps the tube is missing from the inside of the forcing cone.

 

[jds12]

Is that the little metal "pipe" that sticks out of the nozzle a few millimeters? It's still in there.

Would it hurt anything if I just blocked it off with a metal cap screwed into the jet drive housing? I do also have a bilge pump installed.

Thanks again

 

[Cobra Jet Steering LLC]

I would try to find how the water from the pump is getting in the hose. But I guess blocking off the rubber hose would end the problem as long as this is really where the water is getting in the boat and not from one of the other hoses from the pump.
Have you actually seen the water entering the boat via the siphon pickup

 

[jds12]

Yes, I picked up the tube as soon as I saw water building and it was streaming out of the siphon tube.

Not super pressurized but definitely flowing out of it.

 

[Cobra Jet Steering LLC]

I would check and find out the correct length of the pipe since all the ones I have ever seen are about 1 inch long , I just looked at several I have and all of them are 1 inch or longer. maybe your tube is broken off and this is allowing water to be forced inside it and back in the boat, the cone where the pipe is located has a lot of force in it the tube has to be long enough for the passing water to create a suction if it is only a couple millimeters long it won't work properly. this is a jet ski part with 2 of those tubes but you get the idea of how long they need to be.

 

[jds12]

Okay, I'll double check the length and see if it looks broken off.

I appreciate the help. Thanks again

 

[Cobra Jet Steering LLC]

here is another one with 2 however you can see the length of them and anything shorter may be a problem

 

[Bilmon]

from my 240 manual but should be the same. http://www.boatinfo.no/lib/mercury/manuals/240efi_jetdrive.html#/54 Hose is routed up over the exhaust manifold you didn't by chance mount it below the water line? Tube is not as long as those shown in Cobra Jet's pic, top edge of tube is flush with the jet body and lower edge projects maybe a half inch on my m2 pump. Plugging it shouldn't hurt anything as the bilge strainer gets plugged with crud anyway and it's not related to the cooling system, just there to help keep the bilge dry.

 

[jds12]

Ill have to double check that. I'm pretty sure the end with the screen is below the water line, but not the siphon break.

The screen was laying on the bottom of the hull. That's where I assumed it had to be to do it's job.

Appreciate the info, thanks

 

[Bilmon]

Yep, the screen pickup lays on the bottom of the bilge but the siphon break is at the top of the hose as it goes over the engine

 

[Cobra Jet Steering LLC]

Since the water is being pumped in ONLY when the engine is running I don't understand how the anti siphon hose could have anything to do with that. If it were entering when the boat is not in use , just sitting in the water then it would be a suspect.
Somehow the water in the forcing cone is being sent into the siphon tube back to the hull. I would also be sure the reverse hood is ALL the way up in forward since that can deflect some water back at the nozzle. I would try hooking a hose to the pickup tube in the hull and see where it comes out, then block the tube where it sits inside the pump and see if there is some other area that it can leak out since a leak would mean water could be forced inside that spot when the engine is running however I still believe it has something to do with the small tube in the nozzle.