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Hey all,
I recently bought a boat with a clean 2002 F115. The boat fired right up and would run at 6000 RPMs with no issues. During a fishing trip I had the boat idling and/or barely in gear to fight the current I noticed a faint gas smell and then a few minutes later the boat was starving for fuel and if left unattended it would eventually starve out. What I found was I could not get the motor to hold prime. After a few squeezes of the ball all was well. My initial thought was I must be sucking in air. So i went to the tank and check to make sure the vent was not clogged. Then I pulled each hose off and reattached with two hose clamps. I then moved on to the 10 micron filter and prime ball and replaced both of them. The problem proceed. I then got my 3 gallon dingy tank and bypassed everything and problem proceed. After this I discovered that when I trimmed up I would see oil or gas in the water. Further inspection found fuel leaking out of intake silencer. I assumed the motor was flooding. Furthermore, I noticed that it was "making oil" . I thought this played into the flooding narrative quite well but I replaced the thermostat too for good measure.
After reading this forum I knew that VST tanks are infamous for casing all sorts of problems and I figured it was a good maintenance step to do on a new to me motor. My suspicion was the needle in the VST was bad and I was getting too much fuel in the VST. As a result, I was flooding the motor at low speeds. I then changed the inline filter on the motor, cleaned the VST tank, new vst filter and gasket, and replaced a noticeably warn needle and set. I then drop the boat in the water and it idles great. That issue was gone. However, I after I took the boat out for a test run I found that I no longer had any top end. At around 4300 RPMs the motor would bog down and starve for fuel. So I fixed my first issue and now I have a top end issue. So I pulled the VST back off again inspected and reattached thinking I must've hooked something up wrong, left something unplugged ect. Of course no change.
My next idea was that the low pressure pump was bad and causing the "making oil" issue and the holding prime issue. I replaced it with a $219 genuine OEM fuel pump again confident that this would solve my issue. The pump had no effect on the rpm loss however I don't seem to be "making oil" now. (The caveat to that is I haven't put much time on the boat with these problems occurring. Since the boat runs great at low RPMs I am only going outside the no wake zone to apply load and returning to the dock.) Sooo my next step was to clean injectors. I used a battery and compressed air to move a combo of carb cleaner and seafoam through them and did not see any large particles coming out. Everything looked clean but still no power up top.I am now getting tired of throwing parts at this thing,
** I then bought a harbor freight pressure tester (probably not too precise but good enough)
Key on first time 30ish
key on second time up to 40-44
Low RPMS runs from 36-44
4200-4300 the pressure drops to 20 PSI
MAIN QUESTION: So does this drop in pressure signal a bad high pressure pump? bad fuel pressure regulator, VST starving for fuel, motor going into limp mode, bad temp sensor, vacuum leak?
I can pull the vacuum line off the pressure regulator and it run rich at cold idle but once I tried it once the motor was warm after a test run the motor would bog down and eventually die.
I really need your help on this one, I feel like I am just slapping parts on as I go and Im stumped....
Long time user first time poster. I thank you for your help
I recently bought a boat with a clean 2002 F115. The boat fired right up and would run at 6000 RPMs with no issues. During a fishing trip I had the boat idling and/or barely in gear to fight the current I noticed a faint gas smell and then a few minutes later the boat was starving for fuel and if left unattended it would eventually starve out. What I found was I could not get the motor to hold prime. After a few squeezes of the ball all was well. My initial thought was I must be sucking in air. So i went to the tank and check to make sure the vent was not clogged. Then I pulled each hose off and reattached with two hose clamps. I then moved on to the 10 micron filter and prime ball and replaced both of them. The problem proceed. I then got my 3 gallon dingy tank and bypassed everything and problem proceed. After this I discovered that when I trimmed up I would see oil or gas in the water. Further inspection found fuel leaking out of intake silencer. I assumed the motor was flooding. Furthermore, I noticed that it was "making oil" . I thought this played into the flooding narrative quite well but I replaced the thermostat too for good measure.
After reading this forum I knew that VST tanks are infamous for casing all sorts of problems and I figured it was a good maintenance step to do on a new to me motor. My suspicion was the needle in the VST was bad and I was getting too much fuel in the VST. As a result, I was flooding the motor at low speeds. I then changed the inline filter on the motor, cleaned the VST tank, new vst filter and gasket, and replaced a noticeably warn needle and set. I then drop the boat in the water and it idles great. That issue was gone. However, I after I took the boat out for a test run I found that I no longer had any top end. At around 4300 RPMs the motor would bog down and starve for fuel. So I fixed my first issue and now I have a top end issue. So I pulled the VST back off again inspected and reattached thinking I must've hooked something up wrong, left something unplugged ect. Of course no change.
My next idea was that the low pressure pump was bad and causing the "making oil" issue and the holding prime issue. I replaced it with a $219 genuine OEM fuel pump again confident that this would solve my issue. The pump had no effect on the rpm loss however I don't seem to be "making oil" now. (The caveat to that is I haven't put much time on the boat with these problems occurring. Since the boat runs great at low RPMs I am only going outside the no wake zone to apply load and returning to the dock.) Sooo my next step was to clean injectors. I used a battery and compressed air to move a combo of carb cleaner and seafoam through them and did not see any large particles coming out. Everything looked clean but still no power up top.I am now getting tired of throwing parts at this thing,
** I then bought a harbor freight pressure tester (probably not too precise but good enough)
Key on first time 30ish
key on second time up to 40-44
Low RPMS runs from 36-44
4200-4300 the pressure drops to 20 PSI
MAIN QUESTION: So does this drop in pressure signal a bad high pressure pump? bad fuel pressure regulator, VST starving for fuel, motor going into limp mode, bad temp sensor, vacuum leak?
I can pull the vacuum line off the pressure regulator and it run rich at cold idle but once I tried it once the motor was warm after a test run the motor would bog down and eventually die.
I really need your help on this one, I feel like I am just slapping parts on as I go and Im stumped....
Long time user first time poster. I thank you for your help
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