2GM20F revving flat out on it”a own and won’t shut off.

[steve yates]

So I went to the boat today and when I pulled the dipstick there was a flow out of the hole and very runny so definitely diesel in the oil.
Pulled the lift pump and it looks like diaphragm must have gone because there was diesel coming from the back of it.
Glad I found a possible cause so will replace it and put through two oil changes and then see how we go from there.

Yes, my mate just got back to me. He had identical symptoms when I was aboard last year.

The lift pump membrame was leaking, so the lift arm didnt work properly and deisel mixes with the oil. The run away is the oil burning and being used as fuel if I remember rightly.
The fix was to replace the lift pump. He got a cheap one, and then replaced it immediately with the yanmar one, so its probably worth spending the money first time.

 

[wipe_out]

Yes, my mate just got back to me. He had identical symptoms when I was aboard last year.

The lift pump membrame was leaking, so the lift arm didnt work properly and deisel mixes with the oil. The run away is the oil burning and being used as fuel if I remember rightly.
The fix was to replace the lift pump. He got a cheap one, and then replaced it immediately with the yanmar one, so its probably worth spending the money first time.

Thanks Steve, It's good to know I have found the likely cause..

A run away diesel seems to be a more common issue than I would have thought after talking to a number of people yesterday trying to track down a pump.. I am amazed that there is not something like an intake butterfly valve that can be used to shutdown the engine in such a situation built into them for emergencies..

All I ever heard when I had petrol powered boats was how dangerous they were being petrol and they would blow up so diesel was the thing to have.. After this experience is seems diesels have their own way of trying to commit suicide which arguably seems more common than exploding petrol tanks..

 

[scottie]

Thanks Steve, It's good to know I have found the likely cause..

A run away diesel seems to be a more common issue than I would have thought after talking to a number of people yesterday trying to track down a pump.. I am amazed that there is not something like an intake butterfly valve that can be used to shutdown the engine in such a situation built into them for emergencies..

All I ever heard when I had petrol powered boats was how dangerous they were being petrol and they would blow up so diesel was the thing to have.. After this experience is seems diesels have their own way of trying to commit suicide which arguably seems more common than exploding petrol tanks..

Flaps as described are fitted as standard to some much larger engines for this exact reason especially in hazardous applications
not sure just how common a issue it is although perhaps traumatic enough for any instance to be widely discussed

 

[wipe_out]

good result, now would be interested learning where and for how much you'll get your lift pump please.
FWIW, the original is a Mikuni (a v.reputable Jap brand for carbs and fuel systems)

Also how many hours on the engine?

cheers

V.

To answer your questions now the job is done..

Engine has a 1210 engine hours..

For the new pump (Yanmar part), 4x copper washers, gasket, 5L of oil to do two oil changes and two oil filters came to a little over £180.. Job itself was simple enough just in an awkward location on our boat so a lot if working at strange angles..

Ran the engine for about an hour and a half on the pontoon and checked the oil levels every 30 min.. Seemed to be the same so looks like we are in business...

 

[vas]

thanks,

that means lift pump was around 150quid, not cheap...

V.

 

[wipe_out]

thanks,

that means lift pump was around 150quid, not cheap...

V.

There were "cheaper" ones available online but I decided to take the original part from a local agent because it meant I could get it fast and be back on the water this weekend..