Engine stumbling & dying?

[NCSUmoomba]

I searched the old posts, but didn't find exactly what I am looking for. So for the first time on Sunday, I had to get towed back to the ramp. I have a 2001 Outback with the Assault 320 TBI engine that has about 315 hours on it. We ran the boat for about 4 or 5 hours on Sunday, and on our way back to the ramp, the engine began stumbling and cutting out and then it died. We checked everything over, didn't see anything wrong, and after a few minutes, it started back up and we continued. Then it did it again. The guages looked fine, although I was wondering if the temperature was a little bit high (it was pointing midway between the halfway point or straight up, and the 180 mark).

We checked the impeller, and it looked and pumped fine. All the plug wires and connectors were tight. The fuel filter/ water separator is new (I replaced at the end of last season when I winterized), the fuel pump is running and we could see the injectors working. We are baffled. It seemed to start back up after it cooled off and/or sat for several mintues, but eventually wouldn't run at all. A couple of times, when it started back up, it was idling higher than normal and it would "hunt" for idle for a short time.

I thought the Perfect Pass may be going haywire, but I unplugged the actuator, but it had no effect. We also were wondering if the thermostat (I assume the boat has one) was stuck only halfway open and the boat was overheating and going into limp mode, but it would cut all the way off instead of cutting the RPMs to 1600.

Some of the old posts mentioned fuel filters and fuel pressure and water in the gas. I have the spin-on style filter/water separator, is that the only fuel filter on my boat? is there an inline one somewhere also? Isn't it the job of that filter/separator to capture any water in the fuel? I only put 89 octane in the boat, and I do not buy gas from small non name brand stations.

Anyone have any ideas how to diagnose this? Thanks for the help!

[NCSUmoomba]

Anybody have any ideas?

[Yellowmobius]

I would be suspect of H2o in the gas. I assume you have a throttle body. Look in the throttle body for any dropletts of H2o. Did you recently fill? what is the fuel level in the tank?
When it happened to me I noticed it when pulling a tube at slower speeds (angle of the boat and fuel pickup changes and it was getting mostly water)

Doesn't matter where you fill, you can still get a bad fill. Avoid filling when you see a tanker at the gas station. When a tanker fills the gas station tanks they churn up all kinds of crap in the tank, after a few hours the stuff they churn up settles down.

H2o may or may not be the issue but it is one to rule out.

[JesseC]

I would also look for an inline filter that the factory may have installed. Follow the fuel line from the fuel pump all the way to the tank. The spin on fuel/water seperator may have been added later possibly by the dealer.

[RYAN]

Sounds like h20 as well, there is usally one fuel filter on the outbacks. If someone has replaced the orginal fuel pump with another one, look sometimes just above the fuel filter where it attaches to the fuel pump, there could be a much smaller one fuel filter mounted there. Also what helped me out was to take the carb off, remove the float bowls and clean it throughly. Look at the fuel you dump out, check for abnormalites. Change the plugs after you remount it.

[Spicer318]

I had the same thing happen on my 2001 Mobius after I rebuilt the carb, changed the fuel filters, and put in new gas. I started hunting in the electrical system and found a lot of corrosion. I checked all of the components ( starter, coil, distributor, fuel pump, and oil pressure meter). Everything checked fine, I even took the distributor to NAPA (only took out because I had no problems re-timing the engine). I think my biggest problem was that I had a lot of corrosion on my distributor cap, but possibly could have had a loose connection on somewhere in the system. I also added some dry gas to the tank and Lucas cleaner just as a safety.

I am assuming your motor turns over and doesnt catch, thats what mine was doing.

Start small with the dry gas and wire connections. Also try calling indmar they helped me out a lot, as well as skiers choice.

[K_E_N]

Sounds to me more like ignition problem than water in gas. I would think that if it had been water, you wouldn't have ran for 4-5hours with no problem, then it show up; you would have noticed it a bit sooner.
Anyway, replace your distributor cap and rotor and visually inspect all of your wires. If any one wire appears to be rusted or corroded replace them all. Often a distributor cap can have a failure that you can't see that easily. Also, be absolutely certain to check your coil wire. Ignition wires, especially the coil wire, will often begin to fail when put under stress such as higher temps before completely failing.

[BensonWdby]

Just a thought - we have a 99 Mobius that displays similar issues when we start getting low on gas. Since the fuel gauge on these boats is pretty useless we use that as our indicator. We will be running fine all day, and then we go to take someone out of the water and it works, but as we level out the boat chugs, looses power and may die. but we usually throttle back when it first starts showing signs. Then we restart and take it easy back to the dock and re-fill... Works fine after that.

You did say you were boating for 4-5 hours? Depending on what you were doing and your initial tank level you could certainly have been flirting with low enough fuel in the tank to cause this. It almost seems like the location of the fuel pickup in the tanks starts sucking air as the level drops and the boat is at a certain angle...

Good luck
Dave

[kaneboats]

Had a similar issue yesterday and thought I was out of fuel. We had run almost nonstop for 4-5 hours and were heading in when I lost power. I pulled back the throttle and checked everything. All was good and the engine never died. The gauge was showing about 1/4 tank. I idled for a minute or two and decided to try running up again. Ran right up to cruising speed, then full throttle with no more problems. I think when fuel gets down toward the bottom the pickup can suck air sometimes.

[Spicer318]

I was out the other day for about 2 hours and it happened again. all of my connections were fine and gas is going to the carb (carb actually backfired). I took of the distributor and there is oil under my pickup coil. Boat wont start now. Embarrassing tow back to the dock, when I was out of state on a trip with my friends. Starting to think I will have to take it to the dealer. Worst part is I have only had the boat a month.

All fuel filters are clear.

01 Mobius 310HP carbureted

[zabooda]

I've had to replace my electronic igition in my 98 when I bought it in 2002. Some of the same issues. A good mechanic will find the problem.

[thoke]

I have the same problem. 2001 Mobius 310 HP eletronic fuel injection. Just started last week. I spoke with Vince at Discount Inboard Marine this evening and he told me to check pressure on shreader valve on rail coming into throttle body. He also stated that Skiers CHhice had a problem with their fuel pump systems in this year and they make a re-furb kit. I have to find the right size shraeder valve to check, but sounds like a similar problem.