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Intake hose to jabsco pump


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Hi. I have a short length ( approx 1m )  of reinforced clear braided hose from the keel tank to the Jabsco cooling pump on the front of my engine. Has been there since I put the engine in maybe 5 years. Looking at the engine as I passed it the other day I noticed that the hose had collapsed and sucked nearly flat. Does anyone know if there is a better solution which I can still fasten with jubilee clips ( 12mm Internal diameter ) or just keep a spare length of hose and change at regular intervals. Thanks, Kieron.

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33 minutes ago, Fitter kieron said:

Hi. I have a short length ( approx 1m )  of reinforced clear braided hose from the keel tank to the Jabsco cooling pump on the front of my engine. Has been there since I put the engine in maybe 5 years. Looking at the engine as I passed it the other day I noticed that the hose had collapsed and sucked nearly flat. Does anyone know if there is a better solution which I can still fasten with jubilee clips ( 12mm Internal diameter ) or just keep a spare length of hose and change at regular intervals. Thanks, Kieron.

Are you talking about a keel cooling tank or a mud box? I suspect a mud box but you never know.

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Hi Tony. It's a cooling tank which I created in the vee of the boat hull. Boat was originally raw water cooled but I changed to a tank. The Selby and Pocklington canals in this area are bad for weed later in the year.

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Thanks but as its now a sealed circuit - whatever is leaving the engine returns to the tank ready to be sucked out again - so I would not expect the hose to collapse. Maybe flatten on a kink but the coolant should be cold or at least cool so the plastic would soften less.

I have had similar hose on my skin tank to Jabsco pump for the close to 20 years we have owned the boat and it looks like it was fitted from new so about 27 years.

 

I wonder if the tank outlet has partially blocked with rust flakes or something that allows the Jabsco to build up suction.

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There is a strainer on the pickup which I have checked for obvious obstructions . Will blow back down the new hose when fitted to check it is clear. Re coolant temperature I have got a temp gauge taken from a sender on the engine which rarely registers. Only really when working against the tide for prolonged periods, which isn't something I prefer to do but to catch high tide at ocean lock Goole I push against the flood for a couple of hours. The coolant does get hot then but I can still immerse my hand in the tank when I remove the cover so maybe 50-60 deg C. I think that's what the gauge registers. I guess this might have been enough to soften / weaken the hose over the years.

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I doubt you'll learn anything. Just to stop any debris from the tank circulating through the pump & around the system. Maybe seems unnecessary on an engine that would have been raw water cooled but I thought it good practice to put a strainer on the pickup pipe.

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Thanks, a perfectly valid reason, I know I would not have bothered but would have flushed the engine well. For all intents and purposes my Bukh is the same (skin tank & Jabsco) and the impellers last for years. A lot is to do with a low lift cam but  have never seen much impeller scoring like we see on direct cooled boats.

 

Cheers.

 

 

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If you are sucking a vacuum the rubber heater hose is also likely to collapse as it is desgned for positive pressure

For any sort of suction you need a hose with a spiral wire reinforcment designed to prevent collapse under negative pressure.

Not sure if asap sell this, if not look at ARCO industrial range but chose one suitable for hot water service as this is made from better rubber compounds.

You have been lucky using PVC braided pipe at that temperature as it would go soft and degrade quickly, you will probably find it has gone hard by now!

 

 

Edited by adrianh
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8 minutes ago, adrianh said:

If you are sucking a vacuum the rubber heater hose is also likely to collapse as it is desgned for positive pressure

For any sort of suction you need a hose with a spiral wire reinforcment designed to prevent collapse under negative pressure.

Not sure if asap sell this, if not look at ARCO industrial range but chose one suitable for hot water service as this is made from better rubber compounds.

You have been lucky using PVC braided pipe at that temperature as it would go soft and degrade quickly, you will probably find it has gone hard by now!

 

 

 

Like Tony, I don't think there would normally be any significant suction in the first place in the supply pipe to the pump from the skin tank. Therefore an unexplained blockage appears to exist. Undoing pipes and blowing through them may well identify the problem.

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42 minutes ago, adrianh said:

If you are sucking a vacuum the rubber heater hose is also likely to collapse as it is desgned for positive pressure

But there shouldn’t be any suction. It’s a closed loop, so all the pump should be doing is circulating the water by pushing as much as sucking. 

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If Kieron can put his hand in the tank to check the temperate  it suggests to me that it is open so unlike a skin tank where the water going in tends to push the cool water out this one could just increase the level. It sounds to em almost like one of teh staionary engine cooling system that is just a tank of eater gently steaming away.

 

He also said its in the keel so its lower than the engine thus the Jabsco will have to suck to a degree.

 

Still think these may be a blockage although 1/2" or 5/8" pipe seems rather small to me for a main cooling pipe so some may be caused by pipe restriction.

Edited by Tony Brooks
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1 hour ago, Tony Brooks said:

If Kieron can put his hand in the tank to check the temperate  it suggests to me that it is open...

I missed that bit, sorry. 

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Hi. Thanks all for comments / advice on this. I made the tank as a sealed unit with the floor of the boat as the top and a removable plate in the floor to access for maintenance. The idea was to have it ( the top / lid ) bolted down at all times, but in practice I leave it in place but not bolted down just in case I need access on the move for some reason like physically checking the temperature and also so I can check the level and condition of the coolant from time to time. When one of the head gaskets burnt through a few years ago the first sign I noticed was a film of oil on the coolant. Like I mentioned the run to the pump is only short. 1 metre at the most with a lift of around 30cm, so not a great deal of suction required. I will give the pickup pipe / strainer a proper check next time I'm there to fit the new hose I've ordered. The lid is 3mm plate and fits well onto studs recessed in the floor so the system is quite well sealed from outside contaminants even when not secured down.

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