SHETLAND OWNERS ASSOCIATION

So I’m sat here pumping out my holding tank with a motorbike oil extractor! Turns out it’s full when I thought it only had a small amount in it… most of this is not mine, yuk.
I bought a 12v 6.5amp (78watt) self priming macerating pump. It fits perfectly onto the outlet on the gunwhale and has the ability to pump 1.2m (4ft) in height. Unfortunately not to prime - it doesn’t have enough power to lift liquid in the large pipe 90cm to prime itself.
Any ideas as to how I get round this? I’m lucky everything seems to be broken down to liquid as what I’m doing here is not a long term solution.
Thought the venting pipe might be blocked as it was linked but it split when I heated it to get back in shape. I’ll replace the pipes but want to think about my options, need to be able to use public pump outs as well as my own. Maybe I just need a heavyweight pump.

Btw it’s a 100L tank.

I'm not an expert in holding tanks, but I have heard of people pumping air in to push the contents out...

Clive is this for the toilet ?
Our boat has a cassette toilet, if your tank is where the pilots seat is, then that's where are leisure and starter batteries are on our boat.
It's amazing how the same boats are so different, even if they are the same year.

Hi Ian. They seem to vary details in almost every boat! Probably because they were made to order originally. Our batteries are in the same place as you, the holding tank in the picture is the other (starboard) side. We had a porta potti on our previous boat and it always had a chemical odour. This one is completely smell free. It was relined before we picked it up and I asked them to get rid of all the carpet in the head. It is all easy to clean and keep fresh now.
It’s amazing how much there is to do on boats, it’s definitely a hobby! I’ve started at the stern and I’m working my way forward, reading about holding tanks I saw the pipes need replacing every 10 years or so, so that’s a winter job!
Dellquay13 - that’s a good idea, I have a small air compressor that might well do the job.

Some people rig up the footpump from their tender. It would be easier to stop pumping should the s#!t hit the fan.
Maybe the toilet itself could be the pump if you open the airvalve on the flush inlet?
I'm really glad I don't have a holding tank to deal with, I just pump away and give all the Pembrokeshire Surf dudes dysentery...

Update. When we next took the boat out the loo leaked. Turns out an end cap had broken. So I bit the bullet and replaced the pipe work and bought a repair/service kit and a cap. Basically replaced it all. No leaks on testing or when on the water last Sunday.
Yesterday I used my compressor to prime the pump and bingo it worked a treat - thanks Dellquay for the suggestion. All rinsed and clean and woking properly. Custom made some connections in the process!