Mercury 150 V6 EFI Lunges underload

[wdel9]

I have a 1997 Mercury V6 EFI 150 HP. Starts fine, runs great at idle. When I increase idle past 1200 rpm the boat wants to lunge. It lunges then backs off then lunges and backs off. It does not die. When I back off the throttle the boat cruises at slow idle perfectly. I suspect fuel related problem. I took off the fuel filter cannister and dumped into a pan. No water in the fuel and fuel seemed to be clean. The boat has a hand pump primer bulb and gets hard when pumped. Seems to hold pressure. Please advise me of problem or ask questions
Thank you,
wdel

 

[gss036]

Re: Mercury 150 V6 EFI Lunges underload

Check the water/fuel seperator filter and VST (oops) on the engine.

 

[wdel9]

Re: Mercury 150 V6 EFI Lunges underload

What is VSP? I did check that filter no water.

 

[Ram57]

Re: Mercury 150 V6 EFI Lunges underload

I think he ment VST- Vapor Seperator Tank. There is another fuel filter in that tank. If its never been replaced then this filter is probably whats causing the restriction.

 

[wdel9]

Re: Mercury 150 V6 EFI Lunges underload

I found a picture of the VST. I know where that is on my motor. Are you saying I have to take this apart to replace the filter or is it inline? Not sure I saw an inline filter. If I have to take apart the VST to replace the filter do I need a new gasket kit?
The only filter I have seen is the fuel seperator filter. I took that filter off, poured into a shallow pan and there was no water nor dirt. Lubed the seal and replaced this filter as per the owners manuel. I was wondering if there was a filter inside the tank?
Thank you for your responses.

 

[Ram57]

Re: Mercury 150 V6 EFI Lunges underload

Yes the filter is located in the VST itself. I believe the only thing that you need to change is an O-ring not a gasket set.

 

[wdel9]

Re: Mercury 150 V6 EFI Lunges underload

I added 6 oz. of Sea Foam to my gas tank (10 gal. of fuel) and so far as of today the boat runs like new. Thank you all for your help. I will let you know what happens next. By the way what is Sea Foam?