2000 20i strange problem

[boatwakes]

If all you're lacking is power above 2000 rpm go to the ANTI-SIPHON valve located at the top of the fuel tank pick up tube. Replace with an NPT to barb brass fitting (full flow) and test run. If it solves the problem, replace with a NEW aluminum anti-siphon valve from a marine store as running with a full flow non anti-siphon isn't safe.

[Ruger761]

Sorry guys, I disagree with all the above suggestions, you're looking at a throttle/mounted shifter problem. The linkage behind the shifter/throttle mechanism is disengaging and the throttle spring and shifter cable are falling back to idle/neutral position. Then re-engaging and shifting in and out of gear gets the cable pivot points back into position and it goes again. Pull the shifter assembly off the wall and look behind it that both the cable pivot points are anchored and that the mechanism itself doesn't have any damage or missing parts.

Everyone can have their own opinions of whats going on, but when a boat runs fine and then it only does this after sitting for 30 min to 1hr typically points to vapor locking/fuel issue not a shifter issue. A shifter issue would do it no matter how long the boat sat and would even do it on the very first start up and run.

A bad anit-siphon valve can cause vapor locking symptoms when its just a bad valve blocking full fuel flow. No more than they cost if you have a marine store close, Id just replace it with a new one once you try the brass barb full flow testing.

[boatwakes]

Thegreatwhay, are your symptoms of fuel starvation/sluggish engine above 2000rpm instantaneous or after a few seconds of running at those rpm? I agree with TeamAllen that your fuel pressure needs to be monitored during the acceleration and above 2000rpm but we also need to know which motor you're dealing with. I'm assuming Mercruiser so you're fuel pressure should be at 30psi+-2psi at all times. If it deviates lower, try the above mentioned anti-siphon valve resolution, fuel filter replacement or running a small gas can with an unobstructed fuel line picking up from it. If higher, your fuel pressure regulator is at fault. You can purchase the fuel pressure test gauge at any auto parts store, just be sure you get the unit for EFI systems, they usually run about $40 and can test pressure up to 100psi. Unfortunately, there are many symptoms that can present for individual engines and sometimes information gets lost in translation. Do your best to give us as much information and the scenario surrounding your symptoms and when they started so that we can give you the best treatment without too much fodder. Hopefully both of you guys can get your separate issues resolved before too long and get back out on the water. Keep us posted!!!

[thegreatwhay]

Boatwakes,
Thanks so much...Thanks all of you. To answer the question, last year I tested the FP and it was good. What I did not do, is test it while accelerating. I will give that a shot next. I will say that since I wrote the original post, I tried to pull the gas tank, but realized I would have to remove the transmission. So I did do some other hose checks and did find a problem, but not sure if it is the same thing which you are speaking of. See image. The breather tube as I call it, goes up into a one way valve, then goes on to the outside of the boat. The metal elbow that goes outside the boat was 100% clogged with crystalized substance. Gas I suppose. So I cleaned that. The valve could flow freely with out the external outlet being attached, so I assumed the one way valve is ok. Is this particular hose where the anti siphon valve is that you are speaking of? I would probably say it isnt, because you said for the gas pick up. There was an inline filter that I basically removed because I thought it was causing the problem. Note: Both of these things did help the performance a little, but problem still exists. To the best of my knowledge, I cannot find a anti-siphon barb. The barb that exists there is a elbow, with no check valve inside of it.

So I guess I am hoping the FP check will help us decipher what it could be. Pressure regulator is certainly something that I need to take a gander at. As for when it happens, it isnt clockwork. Sometimes it happens immediately on full throttle, sometimes it happens at 3k rpm, and then most of the time, it does happen around the 2200 range. But it is never perfectly consistent.

The engine is a 350 MAG MPI Mercruiser.

Thanks again to all of you. This forum has always been such a great place with lots of great insight.

[thegreatwhay]

For some reason the image seems to have been lost.
Trying again.
tank1.png

[lammbn]

if you read the service bulletin attached in the second post it describes exactly what i am experiencing. I accidently filled up with regular instead of premium this weekend and the problem got a little worse. i want to replace the fuel/water separator just to be sure it is new. not going to lie about the fact that i really havent looked too hard for it but could someone point me in the right direction to find a new one? also i want to inspect the anti-siphon valve, guess i will have to remove the piece over the top of the fuel tank and try to find it.

[Ruger761]

I've been ruining QuickSlivers # 35-802893Q01 available at most walmarts. Far as the siphon valve go to any marine store and get one with a 3/8" barbed end I think it is. Be carefully taking off the our one and installing the new one. Aluminum threads strip out very easy.

I will say on my particular boat I tied both made no diff. Especially as the summer temp increased both water and air. So this year I added the secondary lift pump with no issues yet. And the testing will continue all summer thought the hottest days. Then I will know for sure the fix out of the service bulletin was correct.

[Ruger761]

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[thegreatwhay]

Ok everyone...here is the latest...My Dad and I took the boat out and did a fuel pressure check...there is definitely something happening under load....which now I need to figure out which of the issues may be causing it....
The FP upon start up is about 39 to 40...then while under light acceleration, the FP sticks to about 38...then after acceleration, you can slowly watch the pressure start dropping...all the way down to 10 or so, and of course the boat starts to want to cut out. After letting off the throttle, the pressure will build back up to 40 psi while sitting waiting....then you can repeat and same result...
I have a question though, the manual calls the electric pump with the fuel water separator a Booster... is this different than the fuel pump. (May be stupid question...sorry) I am wondering if that is failing or there may be some blockage inside of it??

Also, is ethanol more dense than gas? Could it be 'heavier' making the pump struggle to get the fuel out of the tank?

Sorry so many questions.

[thegreatwhay]

Lammbn,
Did you ever get your problem resolved? I ended up pulling the fuel booster out and it had some debris that was in front of the small screen prior to going into the pump...Hoping this was the issue, I put everything back together...and still the same problem...so now I have to narrow it down to what I think may be the actual booster = (fuel pump?) or the Pressure Regulator. Both are so dog gone expensive....
Any other suggestions ladies and/or gents?

[boatwakes]

Definitely the regulator is bad so plan on changing it AND the brass adapter that goes into it, they often break when trying to transfer from one regulator to another so we just change them both now. Your high pressure fuel pump is probably okay because the usual symptoms we see with them causes the engine to surge from around 3200rpm to 2800rpm as fuel pressure oscillates from 30psi to about 10psi. The booster pump is the low pressure fuel pump which draws up from the tank and then delivers to the high pressure pump and it's around 4-7psi full time. The one way valve in the fuel tank vent is just that, a check valve to theoretically keep water from entering the tank through the vent. And the anti-siphon valve is connected directly at the top of the fuel tank to the fuel feed hose for the engine.

[thegreatwhay]

Boatwakes,
Just to be clear, there is a regulator on the fuel rail, and one down by the high pressure fuel pump...which one are you speaking of?
Thanks!

[boatwakes]

On the fuel pump. Whats your original serial number?

[thegreatwhay]

Boatwakes,
Not sure if you mean engine serial... But here it is.. 0M390833
I have replaced the antisiphon valve and went ahead and bought the fuel pressure regulator in case the antisiphon valve doesnt work...
The fuel pressure regulator does not look like fun to get to...any recommendations...
You are my hero...

[boatwakes]

Ok your fuel pressure is set at 43psi +- 2psi for that engine. As for the regulator, you must remove the whole pump from the engine mount, just two 9/16" nuts on the mount, and then replace the regulator on the fuel pump. Easiest way to do it includes removing the two fuel lines that go to the pump from the fuel filter and the high pressure line that connects at the back of the engine at the fuel rail. You'll need a special 3/8" fuel line disconnect tool available at the auto parts store to remove the high pressure line. The regulator that's on the fuel rail may also have some debris in it so before any disassembly of the rest of the system, pull the clip on the upper regulator and inspect the internal screen for crap and clean as required. If you want to replace that regulator too, you can use the automotive version part number BWD 23043P for $45 or the mercruiser part number REGULATOR, Fuel Pressure (#885174) for $190. Again, be careful removing the brass fitting from the fuel pump regulator as they like to break so expect that to happen. PM me and I'll give you my shop number and I can walk you through it if you need. Good luck.