Engine runnig rough Help!!!

[Thomas Chobot]

I have a 1998 Pre 2200I with a 350mag with 350HRS on the motor.Yesterday,I did some boarding for a hour.Shut the boat off for a Hour and when I went to start it,it ran rough at idle and when I tryed to put it in gear there was no power.This happened one other time but I was able to somehow clear it out.Both times the Temp outside was in the 80's The tank was almost full.Could this be vapor lock? Any other suggestions? Also,how often should you change your water/fuel seperator?

[TeamAllen]

Change water separator annually. The older boats like our have ,increasingly, been having this fuel vapor lock issue. One theory is the increased ethanol in the fuel.

Most have had success with changing the fuel regulator. It has a rubber diaphragm that deteriorates, I guess.

This year I decided I will run a new Sta-Bil fuel additive for Marine use for Ethanol gas. Here is a link to the thread.
http://tigeowners.com/forum/showthre...hlight=ethanol

[Thomas Chobot]

The other time that the boat was running rough it had Real gas not that crap that they sell now!! Do you think that was why the boat was running rough?

[Thomas Chobot]

Where is the fuel regulator located? Also,are they expensive?

[chpthril]

When was the last time you filled it up? Was it on the water or on the road at a regularly used busy station. If the gas is not recent, it could be vapor lock caused by warm temps acting on winter blend. Low fuel pressure or leaking injector, fuel pump or regulator (anything that lets the pressure bleed off when engine is stopped) will increase the chances of vapor lock. Just like the pressurized coolant system in a car raises the boiling point in order to prevent boiling, we pressurize the fuel for the same reason.

[Thomas Chobot]

The gas was from a busy station in town.Is there a way not to get that vapor lock?

[TeamAllen]

The symptoms most vapor lock issues demonstrate aren't running rough. It is more after a hard constant run then stopping. Often referred to a "Hot Soak". The hot, not running, engine and air temperature inside that closed engine box really build up. When you are ready to go the engine will sputter a little, but not restart for awhile. After it cools down your ready to go again.
Is that what you are experiencing? I have been able to minimize the heat in the engine box by running the fan all the time and letting the boat idle to cool down before I turn it off.

Have you replaced the distributor cap and rotor in a while?

The fuel regulator is located on the engine, down low, closest to the drivers seat. It has a plastic cover for the fuel cooler. The fuel pump is located in there as well. Fuel regulator is $85

http://www.perfprotech.com/store/***...R,2335-90.aspx

[Thomas Chobot]

No I have not changed the distributor cap and rotor since I owned it.Also when you say fuel cooler do you mean the water/fuel seperater.If I can get it running in my driveway with the fake-a-lake when the motor is cold what do you think the problem is? The one other time this happened to me was 3 yrs ago but somehow it stopped surgging and running rough at idle.I have not had any other problems with it.

[dogbert]

The symptoms most vapor lock issues demonstrate aren't running rough. It is more after a hard constant run then stopping. Often referred to a "Hot Soak". The hot, not running, engine and air temperature inside that closed engine box really build up. When you are ready to go the engine will sputter a little, but not restart for awhile. After it cools down your ready to go again.
Is that what you are experiencing? I have been able to minimize the heat in the engine box by running the fan all the time and letting the boat idle to cool down before I turn it off.

Have you replaced the distributor cap and rotor in a while?

The fuel regulator is located on the engine, down low, closest to the drivers seat. It has a plastic cover for the fuel cooler. The fuel pump is located in there as well. Fuel regulator is $85

http://www.perfprotech.com/store/***...R,2335-90.aspx

I'll second the suggestion for running the fan while stopped, especially if you're just picking up a rider or dropping one in.

It sounds more like a vapor lock issue, but the distributor cap is also worth checking.

[TeamAllen]

The fuel cooler is not the water separator. It is where the fuel pump is. It takes fresh lake water in and sends it past the fuel pump and lines to keep the fuel cool. It should look exactly like the diagram in the link I posted in post #7.

I'm not sure why it be "surging" at idle?
I would start with the basic tune-up stuff. Replace plugs, plug wires, cap, rotor, fuel water separator and clean the spark arrestor.

There is also this little check valve located at the fuel tank that has been know to cause problems. It is called the anti siphon valve. Here are a few older threads you can read.
http://tigeowners.com/forum/showthre...i+siphon+valve
http://tigeowners.com/forum/showthre...i+siphon+valve
http://tigeowners.com/forum/showthre...i+siphon+valve
http://tigeowners.com/forum/showthre...i+siphon+valve

[Thomas Chobot]

Where is the Siphon valve located? I am changing the water/fuel separator today.Why wouldn't the siphon valve stick all the time? One more thing that I forgot to mention,the alarm went off for a little while the engine was running rough once but not every time.I try several times to start the engine(ran for 15 sec and shut off)Do you think if I leave the blower on and the radio on I will drain my battery.I only have 1

[dogbert]

If your alarm went of, the engine's computer should have a code associated with it. You'll need to take it to a service place that can read Mercruiser codes. I'd do that before you start swapping out parts.

A question about what you describe as running rough. Is this at idle when you first start it or when you're actually running at a decent amount of RPMs? If it's the former, try pulling out the knob below the throttle (keeps it in neutral) and giving it a little gas. This will usually clear up any fuel supply issues for me from overheated fuel. Otherwise, if it's running rough at RPMs it could be a fuel supply issue. Teamallen mentions a couple of possibilities.

But I'd find out what the code was...it's likely related to your issue.

[Thomas Chobot]

I tryed pulling out the knob and cleaning it out.The first time that it happened 3yrs ago I had it in gear and it cleared out,but not this time.Also,wouldn't the alarm stay on all the time.When the alarm came on I shut it off in about 5 seconds,when restarted it 2mins later and the alarm didn't stay on.

[dogbert]

When my fuel pressure regulator went out, it started alarming at higher RPMS (over 2500), but we really didn't notice much of a difference. I took it to the dealer thinking it was overheating. They were puzzled at first, but then read the codes. When the alarm came on, it would beep 3 times about once every 30 seconds or so.

I'm not saying that it's your fuel pressure regulator, but it could be.

[TeamAllen]

Where is the Siphon valve located? Do you think if I leave the blower on and the radio on I will drain my battery.I only have 1

The anti siphon valve is located right at the fuel tank. It is connected to the fuel line leaving the tank and is screwed into a brass elbow. They are very inexpensive. I only have one battery also, but no stereo. No problems yet.