DF115 stalling after being used at speed

[Majorjob]

Hi all.

I have a DF115 2006 with under 300hrs on it.
It normally operates fine but lately has developed an issue.
After running at speed then idling down and mooring, it would start fine after half an hour or so then idle along fine. But as soon as I begin to throttle up it would stall. Sometimes it would start straight away but I have had it not wanting to start for 10min or so.
It does seem to be worse when I have been using full throttle for a long period of time.
It has only happened since I replaced the low pressure full filter and the water separator.
Any advice appreciated.

[artdf175]

only after replacing filters
I would double check the gaskets to make sure they are not leaking air into the fuel system
run the engine and observe the small inline fuel filter for air bubbles
Art

[Majorjob]

Ok, will do.
Should the fuel primer bulb be firm? I am finding it lacks much resistance.
Thanks again.

[Moonlighter]

A soggy or soft primer bulb thatbis difficult to get to pump and firm up does often indicate an air leak, consistent with what Art mentioned.

[Bcribb]

Hi all.

I have a DF115 2006 with under 300hrs on it.
It normally operates fine but lately has developed an issue.
After running at speed then idling down and mooring, it would start fine after half an hour or so then idle along fine. But as soon as I begin to throttle up it would stall. Sometimes it would start straight away but I have had it not wanting to start for 10min or so.
It does seem to be worse when I have been using full throttle for a long period of time.
It has only happened since I replaced the low pressure full filter and the water separator.
Any advice appreciated.

My DF150 was doing the same thing. I was running on both batteries on my battery switch. One of my batteries was bad so I kept the switch on the good battery. It's been running good every since.. Prior to doing this I had changed the HP fuel filter,had the injectors cleaned, changed lp fuel pump, cleaned vst tank,changed spark plugs,drained fuel tank and cleaned, replaced all fuel hoses and primer bulb,replaced aic valve, cleaned all battery cables and it still did the hesitation on take off and hard to start..Worth a try to run on 1 good battery and make sure your volt meter is showing around 14 volts..

[Majorjob]

Thanks for the info guys.

I did check for air leaks and all seems ok. I did however find that the fuel primer bulb was just not supple enough to pump correctly due to it being a bit old now.
I replaced that and it did eventually pumped up and was firm with no sign of leaking.
However the next morning it was soft again and needed lots of pumping to regain pressure. Should this be the case because I never needed to prime the system previously and would assume once this was done it should remain so.
Thanks in advance.

[artdf175]

Thanks for the info guys.

I did check for air leaks and all seems ok. I did however find that the fuel primer bulb was just not supple enough to pump correctly due to it being a bit old now.
I replaced that and it did eventually pumped up and was firm with no sign of leaking.
However the next morning it was soft again and needed lots of pumping to regain pressure. Should this be the case because I never needed to prime the system previously and would assume once this was done it should remain so.
Thanks in advance.

I recently had a similar problem old primer bulb
it was leaking air into fuel system- the crimps on each end of the bulb failed
when it wasn't running allowed fuel to flow back to the tank that in turn required a lot of pumping just to get fuel to flow to back to the bulb
Art

[Moonlighter]

What brand of primer bulb did you get? There are cheap and nasty ones that often have dodgy valves in them that allow fuell to run back into the tank.

Genuine Suzuki, Yamaha and Merc bulbs are all good and rarely have bad valves. I would avoid most of the after market ones.

If you have used a genuine new bulb, then although you checked, the results still suggest a possible air leak, do they not??

If the bulb was old, possibly some of the fuel lines are also old and deteriorated? Think about that....

Also, in my experience, if the lines are older but are still in OK condition, the best way to ensure a leak free joint is to disconnect lines ar all joins, cut off an inch of the old section where the clamps were, and reclamp on a fresh section of hose. I always add a light coat of gasket goo to the barbs on all lines to help ensure a good seal.

[Majorjob]

Thanks again for the info!

I did buy a cheap primer bulb, I was in a rush so I will look for a quality one.
I think ill just replace all the fuel lines and crimps. I noticed the small crimps on the fuel filter were not a tight as I think they should be so will sort them out also.
Using some gasket goo sounds like a good idea.
Ill let you know how I get on.

Regards.

[catacom225]

Just run it on a spare portable tank and see is the problem persists, aftermarket primers are not the best at times but you should get a few days out of it, it sounds like its not staying pressurized or the VST is not filling up

[Majorjob]

Thanks for that.

What is a VST?

Regards.

[SemperFi_FL]

OP, did you ever get a resolution to this? I'm having the exact same issue. Have replaced primer bulb and fuel/water separator so far, and just ordered parts to replace mechanical fuel pump with electric. Still trying to figure out how to access anti-siphon in my particular boat (Triumph CC).

[Majorjob]

Hi.
Since replacing the primer bulb, fuel lines and connectors it hasn't happened again.
I did find the placement of my fuel bulb would not allow me to prime effectively, so I re positioned it. Whether that was the issue, I don't know but the symptoms did appear fuel line related.
Sorry I cant give you a definitive answer.

Regards.

[SemperFi_FL]

Updating in the hopes this helps some other unfortunate soul. I replaced bulb, fuel/water separator, anti siphon, fuel lines, and the mechanical low pressure fuel pump. These were spread over two weekends, with a little bout on the water after each where I was sure I had fixed the issue, only to be disappointed when it crapped out same as before. After that, I decided hell with it and replaced the low pressure pump with an electric. Sea trial after that and we started up and ran just fine either two or three times during the day. I could feel a little shudder coming up on plane after one stop, but that's it. My best guess is that it's vapor locking, and that mechanical pump didn't have enough oomph to punch through the lock. The electric seems to. No idea why this started so suddenly after a year and a half of flawless joy, but there you have it. I'm just glad the electric pump fixed it, because I was going to have a hard time convincing my wife we needed a whole new boat. Hope someone else sees this at some point in their frustration and is able to save some steps.

[SemperFi_FL]

ETA: Electric fuel pump is Carter brand, part #P4389. I got on Amazon, but Jegs has it as well. I also installed a little inline pressure gauge where the bulb used to be so I can keep an eye on the pressure fluctuations. That part is probably not necessary, but I'm curious about things like that. The pump definitely self-regulates; I can see fluctuations in pressure under different loads. As low as 1PSI on earmuffs to 6 under high load.

I left the low pressure mechanical pump connected. It free flows so it doesn't matter if it's there, and I have the bulb under the helm seat as a backup JUST IN CASE the electric ever dies. Again, probably not necessary, but that's just me.