MPI 350 flooded??

[rough rider]

I recently purchased a 2005 bayliner225. It is powered by the merc 350 MPI. I am new to fuel injection boat engines. After a few hours on the lake we pulled into a cove to anchor and swim as usual for us. A couple hours later when it was time to go, the boat wouldn't start. It cranked over fine and after a while it finally started with a cloud of smoke. It happened again over the weekend and I don't know how to diagnose this problem. Where do I start? Do I need to get a code reader to begin? The other boat we just sold had a two barrel Rochester and it was no problem to get started even if it were flooded. Any ideas?

 

[alldodge]

I recently purchased a 2005 bayliner225. It is powered by the merc 350 MPI. I am new to fuel injection boat engines. After a few hours on the lake we pulled into a cove to anchor and swim as usual for us. A couple hours later when it was time to go, the boat wouldn't start. It cranked over fine and after a while it finally started with a cloud of smoke. It happened again over the weekend and I don't know how to diagnose this problem. Where do I start? Do I need to get a code reader to begin? The other boat we just sold had a two barrel Rochester and it was no problem to get started even if it were flooded. Any ideas?

When you were trying to start it, was it like it might barely hit every once in a while but nothing steady?

Does it always fire right up if cold, or if you stop for just a brief time (like time to change tubers)?

Once you get if fired up it runs fine until you stop and let it sit again for a longer time?

 

[rough rider]

It always starts fine after brief shut down.

When the motors cold or been a week or more since last started it usually takes 3-5 seconds of cranking and she comes alive.

When it wouldn't start I do remember it almost starting a couple times but I can't remember it to clearly. It was last month and a few trips ago. It has me worried because it happened again over the weekend and I don't want to get stranded with the kids on the boat. Heading to lake havasu this weekend and trying to get all the bases covered.

 

[alldodge]

Starting to me like your dealing with vapor lock. When the engine gets hot after a good run then you slow down and stop. The heat start soaking into the fuel lines and components. There are Merc bulletins out there and many threads. Best thing you can do is when going to stop for a while, is let the engine idle for a longer period of time. Turn the blower on and let it run while your idling. Opening the engine hatch can also help, just need to get as much heat out of the engine bay.

Another think I have found which can help is using non-ethanol gas (if you can find it), or modifying your fuel system which will take the fuel return line back to the tank instead of the fuel filter

 

[rough rider]

That's very interesting. So what clears the vapor lock? I don't know what to do next time it happens.

 

[thumpar]

Open the hatch and let it cool down. If it doesn't start right up put the throttle only all the way forward. Always works for me.

 

[alldodge]

That's very interesting. So what clears the vapor lock? I don't know what to do next time it happens.

If your symptoms are what I mentioned above then you need to get the vapor out. Giving it some throttle can help and opening the hatch, blowers all help. Going full WOT cause the injectors not to fire, in flood mode, go to 80% throttle or so. Other methods are as previously mentioned

 

[rough rider]

Well I've been on the lake for two days and both days were vapor locked. I tried all the suggestions given and so far none seem to work.
The throttle position doesn't help at all.
The temperature this weekend was 117 degrees.
What seemed to work consistently was to try to start the motor four or five times and then wait five minutes.
After the five minutes, she would start right up. Why isn't there a way to push fuel through the fuel rails and into the tank? There has to be a way to fix this issue. There are lots of boats out here this weekend that probably have this engine.
How and where can I add a line to let the vapor out?

 

[alldodge]

The best way to fix it is to disconnect the return line going back to the filter and send it back to the tank. This can be done if you have a return fitting on your tank not being used, or by connection the return line back to the gas fill hose/neck. There are some places which do this work, but it needs to be done correctly. This pic illustrates how its done. Some engine manufactures already do this such as Indmar.

 

[rough rider]

So returning to the tank instead of the filter is going to fix this? Is it because the tank is vented and the vapor will be pushed by the fuel being pumped in?

 

[alldodge]

Once vapor comes from boiling it needs to go somewhere. Same thing would happen if the fuel system was dry, it needs to be bleed. So when the pump turns on prior to starting it will push vapor if any back to the tank and escape. If vapor goes into the filter it just recirculates. This is just my thoughts but those that have done the return to tank, all vapor lock issues are gone

 

[rough rider]

I am surprised that merc would not have done the return to the tank to begin with. This has to be a common problem. I just don't know why I am the only one on the lake trying to start there engine on the hot afternoons in lake havasu.
I have read so many threads on vapor lock that I am thoroughly confused on how to fix it.
This return line to the tank makes the most sense to me so far.
I saw that merc has a bulletin calling for adding a check valve in the line.
I also saw that adding a low pressure fuel pump into the fuel system somehow helped some people but there're still not pushing the vapor anywhere to escape?

 

[Fun Times]

What is your engine serial number.

Also being an 2005 you may already have a check valve but in what location is the question and that will depend on what drain system you have.

Standard Cooling System(7 Point Drain)item#13
Standard Cooling System(Single and 3 Point Drain)Item #2

Sometimes the check valves can fail (stuck open) allowing hot water to flow down to the fuel pump...That is if you have the Gen 2 cool fuel system which is questionable being an 05 engine model. Do you have an Alpha or Bravo drive?

 

[rough rider]

It is an alpha drive for sure.
I do not have the engine SN with me.
I see the check valve in the parts drawing but can not picture in my head where that check valve is. I will see where it is and if it has one today.

 

[rough rider]

Does anyone have any idea if the vapor lock happens before the fuel pump or after?

 

[skippy2235]

I think it is the IAC, Idle Air Control valve, that is dirty or not working correctly, Also could be the ECT, Engine coolant temp sending unit.
the IAC allows air flow past the throttle to control start and idle. The ECT tells the computer how hot the engine is. If getting wrong readings, then computer gives false fuel flow.
You Tube has lots of info about these items,

 

[rough rider]

I'll check those videos out today. Thank you

 

[alldodge]

Does anyone have any idea if the vapor lock happens before the fuel pump or after?

After the pump, on the high pressure side

 

[Fun Times]

https://en.wikipedia.org/wiki/Vapor_lock

Vapor lock is a problem that mostly affects gasoline-fueled internal combustion engines.
It occurs when the liquid fuel changes state from liquid to gas while still in the fuel delivery system. This disrupts the operation of the fuel pump, causing loss of feed pressure to the carburetor or fuel injection system, resulting in transient loss of power or complete stalling. Restarting the engine from this state may be difficult.
The fuel can vaporize due to being heated by the engine, by the local climate or due to a lower boiling point at high altitude. In regions where higher volatility fuels are used during the winter to improve the starting of the engine, the use of "winter" fuels during the summer can cause vapor lock to occur more readily.

In some cases you can usually help remove vapor locking quicker by pushing in on the fuel schrader valve found on the fuel rail. Have a rag handy though. https://images.search.yahoo.com/sear...fp&fr2=piv-web

Is the fuel old by chance? What station (brand) do you typically use?

 

[skippy2235]

On my boat, I have a fuel heat exchanger. First thing raw water gets to is the fuel heat exchanger. then goes to the power steering heat exchanger, then the engine.