2003 Mercury EFI 4 Stroke 115 HP

[LSaulmon]

I have a 03 Merc. 115, it frequently stalls when shifting between forward, reverse, and back to idle. I recently changed the fuel filter (attached to front of motor), drained the gas tanks (one plastic and one alluminum), replaced the fuel lines, spark plugs, and changed the oil and oil filter. I also added a 10 micro water / gas filter. Boat has fresh fuel and I added sea foam. I ran the boat last weekend, started out great, but after sitting parked for a few hours, our next trip was the exact opposite, engine ran rough cutting in and out, at full throttle the engine would start coughing and fall on its face. I spoke with a boat mechanic who recommends removing the fuel injectors and having them cleaned at a lab - cost of $170 - I asked another boat mechanic (second opinion) and they recommend ( at $70 per hour ) having them diagnose the engine and check the hi pressure fuel filter. I am at a cross road, I don't want to throw money down on a guess or assumption of the problem, that could be expensive. If anyone has any suggestions from past experiences, I would welcome your thougths on the matter.

 

[hauki]

Re: 2003 Mercury EFI 4 Stroke 115 HP

Did you get the issue resolved?
I have a 2001 115 4-stroke that stranded me.
It sputtered a couple of times at WOT and, after I stopped to fish (using my electric trolling motor), the Merc wouldn't start. It would idle and then die as soon as I put it into gear.
Luckily someone saw me and I got a tow back.
The next day it started fine and once again at full throttle it started to sputter and miss. Once I slowed down and stopped it wouldn't start again.
Back at shore I switched gas tanks (from built-in to cruise-a-day) and it didn't help.
Any answers?

 

[patbalmos]

Re: 2003 Mercury EFI 4 Stroke 115 HP

You more than likely need to have the injectors cleaned and have the screen in the vst pump cleaned also. to clean the vst screen you need to pull the intake manifold off and take the cover off of the vst tank the screen is located on the bottom of the high pressure pump. be sure to order a new gasket for the top of the vst housing. 170 sounds to high for the injectors they should cost around 25 a piece. there is a company located locally here that does a very good job and provides a flow readout both before and after cleaning.

 

[spicoastie]

Re: 2003 Mercury EFI 4 Stroke 115 HP

The 115 have a fsm(fuel supply module) pull fsm and check the pressure regulator for debris and make sure the attaching hose did not split, if that hose splits it will flood your intake manifold making the engine run rich and foul plugs. hope this helps have replaced many with these symptoms.

Brett

 

[cbmel]

Re: 2003 Mercury EFI 4 Stroke 115 HP

The 115 have a fsm(fuel supply module) pull fsm and check the pressure regulator for debris and make sure the attaching hose did not split, if that hose splits it will flood your intake manifold making the engine run rich and foul plugs. hope this helps have replaced many with these symptoms.

Brett

I have a 90 EFI that suddenly began running like crud. It's on a pontoon boat on a lift. How hard is it to pull the FSM? I suspect that the "I don't like ethanol" hose has split.

 

[ampalan]

Re: 2003 Mercury EFI 4 Stroke 115 HP

I bought a one of these motors brand new. Had the same problems along with several others. Had to replace the high pressure fuel pump and the injectors.
Along with that the powerhead was replaced in the first 3 months of operation. The control module went out the 3rd year. Now it's setting in the yard with a dead short in the electrical.
I admit I use this boat alot but it's been rather expensive to keep in the water. But when it is running... it does run well. Oh i almost forgot.... had to replace the coil as well.