Vapor Lock

[sbagley]

New 05 Mobius LSV has vapor locked (or at least that's what we think it is). After running the boat for 3 or 4 hours the boat started popping, chugging, backfiring and after about 30 seconds just dies.

It has happened anywhere from 75 degrees to over 100. I talked with the dealer and Indmar while stuck on the lake for 8 hours troubleshooting (we were on a trip 6 or 7 hours from the dealership). Both the dealer and Indmar think it was vapor lock.

We tried cooling the lines, removing gas cap and numerous other things - no luck. We did get it running for a few minutes then it just died again. Since owning the boat 3 times we've gone on trips and everytime the boat has died.

I guess this boat was a mistake? Any ideas on what could be causing the vapor lock - if that's what it is?

Thanks.

[smokedog2]

well, it is not vapor lock. Vapor lock is a starting issue, not a running issue. The gas cap vent keeps the tank from pulling a vacuum as the gas is used, but that is not vapor lock. Vapor lock is gas/water/air vapor in the fuel lines, I've never heard of it in a fuel injection engine (but I do not get out much).

Drain the gas tank & change the fuel filter if getting to the dealer is a pain, otherwise hand it off to them.

If it were me, I'd change the filter, put some water eater in the tank and go for a test run (with another boat).

All this assumes all the gauges look normal.

I'd bet money this is a fuel issue.

SD2

[BLKOUTLS]

sbagley
what engine do you have. If you where able to restart and run for a few minutes and then it died again I would look at something other than vlock. All the gas would run out of the bowls and the boat probably would only run for about 15/20 seconds, if it is a carb and truly vlocked. Give a little more info on boat,gas, filters, fuel lines ,oil pressure,and such.

chris

Thanks a bunch for the replies,

Its the EFI 320hp engine. (Fuel Injected Engine - LSV option from the carb 310hp). I got this for easy starting since in Utah where I live the lake elevations vary from about 3,000 feet to 6,500 feet.

--------

I did get it to run again after being stuck on the lake for 8 hours. It ran for 10-15 minutes then when I slowed down and put it in neutral, it died again and wouldn't start.

Drove home and took it back to the dealer, they talked with Indmar and decided that I just ran it too long without proper ventilation which caused the vapor lock. Seemed like a really lame response but I went ahead and took it back out last night.

After running it for about an hour to an hour and a half it killed while I was idling in neutral. It started back up and ran for about a half hour then died for good. This time I kept the blower on the entire time. The gauges all looked right the entire time - Temp: 170-180, Oil Pressure, etc. everything was normal.

Just as it died it was chugging and while in neutral the RPMs would go up and down without me touching the throttle.

I took it back in first thing this morning and they are going to look at it again.

Thanks again for the replies. I know and understand motorcycle (motocross) engines real well, I raced them for years but I don't know much about boats.

Again any ideas are very welcome as we try to figure out what's going on. I've now been stranded 4 times with this boat and my family is getting pretty worried to even go out on it.

Thanks

[sbagley]

Thanks a bunch for the replies,

Its the EFI 320hp engine. (Fuel Injected Engine - LSV option from the carb 310hp). I got this for easy starting since in Utah where I live the lake elevations vary from about 3,000 feet to 6,500 feet.

--------

I did get it to run again after being stuck on the lake for 8 hours. It ran for 10-15 minutes then when I slowed down and put it in neutral, it died again and wouldn't start.

Drove home and took it back to the dealer, they talked with Indmar and decided that I just ran it too long without proper ventilation which caused the vapor lock. Seemed like a really lame response but I went ahead and took it back out last night.

After running it for about an hour to an hour and a half it killed while I was idling in neutral. It started back up and ran for about a half hour then died for good. This time I kept the blower on the entire time. The gauges all looked right the entire time - Temp: 170-180, Oil Pressure, etc. everything was normal.

Just as it died it was chugging and while in neutral the RPMs would go up and down without me touching the throttle.

I took it back in first thing this morning and they are going to look at it again.

Thanks again for the replies. I know and understand motorcycle (motocross) engines real well, I raced them for years but I don't know much about boats.

Again any ideas are very welcome as we try to figure out what's going on. I've now been stranded 4 times with this boat and my family is getting pretty worried to even go out on it.

Thanks

[dkjbama92mari]

sbagley,

I concur with smokedog. I believe it is definitely a fuel issue. To be honest, my gut makes me think that its as simple as water in the gas. When I was young, any time our boat had a running issue, my father blamed it on water in the gas, and 95% of the time he was right.

Checking both the Moomba and Indmar owners manuals, i didnt see anything about a water separator. The moomba one mentions a fuel filter, thats it. The chugging and backfiring you describe usually indicates a lean air to fuel ratio. Since you have EFI, you know that the engine is getting the right amount of fuel. The only way it couldnt would be if there was a sensor problem, and tha would thow a code and turn your check engine light on. If there is water in he gas, the computer still thinks its giving the engine the right amount of fuel, but it really isnt. For an example: the computer calculates that 10 units of fuel per firing cycle is appropriate. If there is, just for example, 20% water mixed with the fuel, the computer thinks its giving the engine the ideal amount. But in reality, it is only getting 8 units of fuel per firing cycle. Presto, instant lean condition.

Now i know what you're thinking. Hmm, 20% of a 40 gallon tank would be 8 gallons of water; thats alot. Here's the catch; gas and water may collude, but they will not mix. If left to sit, the water will eventually just settle back to the bottom of the tank. When sitting on the bottom it is probably below the level of the fuel intake. Once it gets shook up, all it takes is for some of that water to get sucked into the pump and you’ve got problems.

Here’s another point. An engine can sometimes run at higher RPMs with some water in the gas, but it will NOT at lower RPMs. And once it dies, it will be difficult if not impossible to restart. This would explain why you got it to run awhile till you slowed down and it died again. I’m thinking that when you did get it to crank, you just got lucky and the pump managed to suck up some fuel that didn’t have quite so much water in it and got the engine fired up.

Just in case you didn’t know. The main way of getting water in gas is condensation in the tank. It happens when you store the boat with less than a full tank of gas. Everything gets nice and warm inside the tank during the day. Then, when night comes, the cool night air cools the walls of the fuel tank causing the moist air inside to condense on the walls. If you think about it, after a week or so, this could amount a pretty good amount of water. Even if this turns out to not be the source of your problem, I URGE you to just get in the practice of filling your tank on the way home from a day on the lake. If the tank is full, there isn’t anywhere in the tank where water can condense at.

OK, I apologize. I’ve managed to turn an extremely simple theory of the source of your problem into a thesis paper. Oh well, any thesis needs a conclusion so here goes. If you haven’t taken smokedog’s advise, then do so. Drain the tank completely, change the fuel filter, and refill with fresh gas. It’s a likely cause and a simple fix you should consider before you just start guessing and throwing parts at the boat out of pure speculation.

Good luck, hope this helps, and I REALLY hope I’m right after typing this much.

Cheers,
DKJ

[greygoose]

In your last post you stated that the RPMs jumped arond and the boat went dead.
Make sure that all electrical connections from you seding units such as the oil sending unit are tight. There is a connection from the oil sending unit that goes to your gauge and one that goes to your computer. Make sure the connections are tight. Just a thought.

[Dave A]

Could be a sensor issue. My TPS sensor was bad when I first picked up my boat. It ran for about 4 hrs, then when I was coming in to the dock at an idle, the rpms would fluctuate and then the engine would die. It restarted, but it was all I could do to keep it running to get it on the trailer. I was in a no wake zone, so I'm not sure it the boat would have continued to run if I was at cruising speed or not. I belive there are 3 sensors, the TPS, the MAP, and something else, not sure sorry. Ask you dealer about this. I have not had a problem since and my dealer told me Indmar had received a bad batch of sensors and had no way of tracking them. Good luck, hope this helps.

[Yellowmobius]

Water in the gas sounds like a good suspect.
Drain your tank or have it drained you might be surprised.

P.S. Don't fill at a gas staion if you see a tanker there. They mix up all the crap in the bottom of the tanks when they fill them. It is a good source of engine running problems.

[dkjbama92mari]

BTW guys,
Please don't discount my opinion as a newbie because of my low post count. I'm at 159 on the Supra board. I just got bored and decided to throw my $.02 here because the service forum there is pretty dead and i enjoy working and discussing mechanical things.

Like i said before, check the cheap and simple things before you start spending money throwing parts at it on mere speculation.

Cheers,
DKJ