MP 5.7 Fuel related problem

[bsfreefalllt]

I have a new to me 2005 24V with the MP 5.7. I've had no problems with it 3-4 days on the lake. 2 days ago, it cranked fine when cold. After pulling some wakeboard and tubing runs and wavesurf run...it wouldn't crank well. It had to turn over almost a minute before it would barely struggle to fire up. I took it out again today and same thing. Cold started fine. Hot didn't want to crank. It also has a long continuous alarm that occurs with key on but goes away when cranked. The center small red light is on.

I checked the fuel pressure with key on and when cranked which was good 55 psi.

I also think that the power is not as good as it was.

The problem started after we tried our first port wakesurf...loaded up rear locker and front ballast to about 700 lbs. Put a suck gate on. Ran it about 1000 yards without a very good wave and decided to bag it for the day. I read another post about water getting into the gas tank from the poorly positioned air vent below the gas fill on the far back corner.

So, I'm thinking maybe it's water in the fuel. After purchasing the boat, I put in 20 gallons of ethanol fuel to whatever the previous owner had. It ran fine until the wavesurf event. Not really thinking clearly I decided to fill up with fresh ethanol-free gas. It took 29 gallons and I added 2 bottles of iso Heet. The same thing happened again except when I opened the engine bay I saw 3-4 pillows of white smoke coming from the rear of the motor. I got it started and pulled it on the trailer planning on taking to a mechanic. Unfortunately, every mechanic I've talked to said they can't pull codes for MP or they are swamped with winterizing work and can't get to it for a month.

SO I have time to try my best to sort it out with a buddy. How can I siphon some fuel out to see if there is water? I understand from other posts that you can't come from the filling.

If there is water, what do I need to do to get it cleared up?

How many gallons is the fuel tank?

Thanks,
Brent

[TigeFamily]

Easiest way to siphon the gas is probably by disconnecting the fuel fill line from the gas tank and doing it from there (if your floor is removable).

Other things to check that are maintenance items and tend to cause issues if not kept up with.... distributor cap, plugs and plug wires. Have you replaced the fuel filters?
If that engine has a carb, you may need a rebuild if it sat for any period of time with ethenol fuel in there since when phase separation happens, it turns to gunk and will clog up a carb quick. Doesnt sound like this is the case tho if it starts cold but doesnt want to start hot. Kindof sounds like maybe vapor lock is happening?

Consider Vapor lock if it's a hot day. “Vapor lock 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” Open the dog house to allow cool air into the engine 9
compartment. This may be a good practice while you are figuring out what to try next.
“It's easy to open the dog box and let the motor/fuel lines cool for 10 minutes. If you
have a cool rag place it on the fuel lines for a short time and give it another shot” .
10
Tips relating to vapor lock include “key-up four or five times before trying to start to get
the fuel pump to prime with cool gas and clear the vapor lock at the rail. If that doesn't
work, and you want to CONFIRM vapor lock, put a wet rag over the schrader valve on
the fuel rail and vent it. If you get air, you've got vapor lock, if you get raw fuel probably
not vapor lock.

Check out this thread, has a link to a pdf "no start trouble shooting guide" that you could look thru.
https://www.themalibucrew.com/index....oubleshooting/

[nhunt]

bsfreefalllt - I've had a very similar problem for the last few years. I have a 2004 22V, MP 335. Cold start - no problem. But engine would struggle to start when warm. Thought we ran out of gas a couple weeks ago, but when filled up with gas, it didn't take a full tank (31.5 gallons, it's a 40 gallon tank). Just replaced the fuel filter/pump (Gforce), and it still won't turn. We think it's the throttle position sensor now?
Let me know if you figured it out! Definitely trying to get this resolved as we only have 3-4 weeks left at best!
Thanks!!!

[teachercop]

Any resolution to this issue?

[okiepilgrim]

Would love an update as well bsfree if you're ever back on. Think I'm having vapor lock issues as well. Fine some days, not others. But I've noticed my port exhaust manifold _sometimes_ gets a lot hotter than my starboard, so I'm leaning towards a partial blockage in my cooling system. Since the fuel filter (and fuel cooler) are on that side of the engine, I'm thinking that's a primary contributor. BUT the main thing I want to ask about is the loud beep. Because mine's been doing that for a few weeks now. Taped up the "speaker" so I can at least hear whether or not the engine starts, but really curious about this. Can't get into the shop for another week and an half.