Sound like vapor lock / water in tank / fuel pump?? - 6.2 MPI - Help...

[stereoman405]

I'm about ready to tear my hair out here. I just picked up an '04 Ebbtide 2300 Sport Cuddy with Merc 6.2 BIII w/ exhaust and 200 hours on the clock. I'll try to list the order of events to see if this sounds like a vapor lock.

- Boat was stored by PO with half tank full of gas over winter.

- I ran the boat hard for 60 minutes after purchasing and it ran fine.

- Put 30 gallons in for June 30th weekend. Temp was mid 70's, ran great for an hour of moderate cruising.

- Brought it out July 4th evening (temp low 60's). After 15 minutes of 3000RPM cruising got some decent coughing and sputtering. Backed off throttle and problem went away. Drove easy for another 30 minutes without issue. (Meter showed just under 1/4 tank).

- Came back a week later took it out at night (60's) and low fuel alarm went off saying I had 3 gallons of gas left after 5 minutes. 1/4 tank needle drops to E. . I get a few coughs and sputters but nurse her to the dock and put 30 gallons and put 2 bottles of red Heet in. Boat coughs and splutters like crazy on the 15 minute trip home.

- Next day I swap out water separator and go for 2 25 minute easy evening cruises (temp low 60's). Runs like a champ.

- Come back the next week, toss the family in (low 80's) run WOT for a minute then back off to 3000RPMs and it sputters HARD and almost dies after a couple minutes. I shut it off for a couple minutes, then get it up to cruise again, after 5 more minutes it dies HARD. For the next 45 minutes I have to let it sit for 5 minutes, then it runs for 30-45 seconds and dies again, never getting over 1500RPM's without choking. I hop scotch to the dock for 2 miles doing this.

- I park it at friend's dock and let it sit for a couple hours. In the mean time I clean a tiny bit of corrosion off the rotor and contacts in the cap and install a bypass tube to skip an inline filter that comes before the primary pump and water separator. (Thinking its plugged up.) I fire her up and cruise at 3000 - 3500 RPM's for 5-10 minutes. No issues. I go WOT for 5 minutes and the sputtering comes back moderately. I immediately put a new water separator on thinking their is just a **** load of water in the tank. I don't see any obvious signs of water in it but put on the new one for good measure. I didn't realize you need to prefill them so I bleed the air out of the fuel rail by cycling the pump a few times with the bleeder depressed. Boat cruises great for a few more minutes, then after another WOT run the hesitation comes back.

- I park it for the night and talk to a local mechanic the next day. He says that Heet was a horrible idea and gave me a few pointers. I throw a 100 gallon dose of stabil in, add 50 gallons of gas to top off the tank with octane booster, check the detent ball on the tank outlet, back fed air into the pickup tube to make sure its clear, and took the cover off the cool fuel unit. I also inspected the tank with a flashlight thorough the sending unit hatch and didn't see a spec of crud anywhere. After this the boat ran fine cruising for a 15 minute and two 40 minute hauls. At the end of the last ride I had her WOT for a few minutes and the hesitation came back. This was an 80 degree day with 5 adults and 70 gallons of fuel.

- Next day I have 10 passengers, (took 4 minutes of WOT to finally get on plane comfortably) and after 15 minutes of cruising at 4000RPMs it came back again. I floated for a while, drove to a resort, we left an hour later and it ran fine 25 minutes back home.

- Next day same story. Cruises fine for 10-15 minutes ,then after WOT for 2-3 minutes is hesitates. (2000rpm drop). Motor doesn't die all the way, just feels like it wants to. As soon as I back the throttle off she starts running again.

So strange. The only consistency is that it SEEMS worse when its hot outside and a long WOT pull will set it off. It also always fires right back up when I do shut it off. When I had the 'hop scotch' experience I thought the high pressure pump sounded odd, but now it doesn't. The mechanic I talked to said Heet can be hard on pumps so I'm thinking maybe that was affecting something.

Arrgggg. My big vacation starts on Friday and I'm trying to figure out what to do. Can't tell if its the cool fuel acting up, failing pump, or just remnants of bad gas.... HELP!! Ignition coil maybe?? It just FEELS like a fuel delivery issue, but the motor pretty much cuts out when this acts up so it could be ignition related I guess. But after all my tinkering and seeing some improvement it seems like fuel delivery has to be part of the mix.

[Throttle Fever]

Screen in the fuel injectors clogged or gummed up (explains the stumble at wot and there after). Or tank pick up check valve clogged up? Just thoughts. Pete

[JRider]

Still sounds like water to me. Isopropyl alcohol (red heat) will not hurt anything.

[johnlaskowski]

yes it will causes more vapor lock. fuel u buy on the water has no ethanol in it thats part why its so expensive. im agreeing with pete as i had the same prob. read my post in the do it yourself under MPI owners FYI.

[Griff]

It really sounds like water in the fuel. Take the fuel water sep off and dump it into a clear glass jar and let it stand for about 30 mins. Check for separation. The water will be on the bottom.

It is definately not vapor lock. Vapor lock happens when trying to restart a hot engine.

[stereoman405]

Screen in the fuel injectors clogged or gummed up (explains the stumble at wot and there after). Or tank pick up check valve clogged up? Just thoughts. Pete

I already checked the check valve and didn't notice anything. Where are the injector screens? On each individual injector or is there a main one entering the fuel rail?

If it is still gas in the tank, how exactly do I go about taking care of it? I guess it can't be too bad since the boat runs fine 90% of the time, but will changing separators a few more times do it, or can I just keep dumping this one out? I still have 50 gallons in there and the boat is moored....

[stereoman405]

yes it will causes more vapor lock. fuel u buy on the water has no ethanol in it thats part why its so expensive. im agreeing with pete as i had the same prob. read my post in the do it yourself under MPI owners FYI.

Interesting.... I just read your post. There was some serious popping when I was doing the 'hop scotch'. And I believe there is still a little going on when the issue happens.

With your clogged injector screen, did the issue happen right away, or was it a slow progression? It just seems crazy to my that this happened all of a sudden when I got below 1/8 of a tank.

Also where does this crap come from? I have two inline filters and the screen filters on the fuel cooler. If its just varnish why would it have manifested so quickly out of nowhere? Either way I'll probably clean them, just trying to wrap my head around this.

[Throttle Fever]

I already checked the check valve and didn't notice anything. Where are the injector screens? On each individual injector or is there a main one entering the fuel rail?

If it is still gas in the tank, how exactly do I go about taking care of it? I guess it can't be too bad since the boat runs fine 90% of the time, but will changing separators a few more times do it, or can I just keep dumping this one out? I still have 50 gallons in there and the boat is moored....

The gunk will build up on the screens over time to where it restricts the flow. Usually happens so gradually you don't notice, until one day it starts cutting out at higher rpm. The screens are in each unit injector. Fuel filters only filter to about 30 micron's at best (depending on the filter, some are 100 micron). That leaves alot passing by. Go with the filter changes a few more times and see what happens. You will know, it will not cure itself, you will start loosing more and more rpm. See if you can check you fuel pressure at all rpms and then you will be able to rule out at what end of the fuel system you are fighting. Pete

[Griff]

You can just dump the water sep filters and reuse them if it water in the fuel.

[jeffswav]

If the boat is running like crap, I would not just keep running it. You can do major damage to your engine by continuing to run it. You could have bad fuel, if you are running E10 you could have water separation. This has been covered many times and you can do a search and find many threads on this topic. I would also do a complete tune up, plugs, wires, cap, rotor, filters. You may also want to check the pickup in the tank, the screen may be clogged.