stereoman405

Good advice. I've was starting to get a little worried that if it was a fuel pump issue that I might be running her lean.

I tried pulling the pickup tube out but it felt like there was something larger than the opening keeping it from coming out. I was afraid that if I pulled to hard it would knock whatever it is into the tank. Is this normal? There is no access hatch in the tank itself that would allow you to unscrew something from inside the tank. Is there some sort of stiff mesh or something that could just be binding up?

JRider

Even if it did vapor lock the Isopropyl will not hurt anything. Since it is less than 1% of his fuel I doubt it would contribute much to vapor lock. Ethanol can eat composites and rubber, Isopropyl does not.

jeffswav

How old is the fuel in the boat? It sounds like you had old fuel in the boat when you bought it. Then you simply added more fuel on top of the bad fuel. Now you have really old fuel with month old fuel sitting in your tank.
If this is the case pump it all out and recyle or whatever you can do with it. Only put the amount of fuel in the tank that you will use in a couple of weeks. I took out the tops of my rod berrings with bad fuel about 4 years ago. Take a look at my nightmare story, if this is what you have done you may have already done damage.
http://www.offshoreonly.com/forums/g...0-ethanol.html

stereoman405

I bought the boat with 30 gallons in it (from previous fall when PO winterized it), I ran it down slightly, then put 25 gallons from a gas station in. Ran fine for a few outings, then according to my Smartcraft setup the issue started when I was in the 6-8 gallons left in the tank range. I then ran it down to 1-3 gallons before puting another 28 in with 2 bottles of red heet.

So theoretically if my Smartcraft is even moderatley accurate I should've purged all of last season's gas out down to a few gallons. It could easily mean I still have a water bubble in there though.... Just seems odd that this started when she was near empty.

I hope I didn't casue any permanant dmage. My gut reaction was a water issue so I figured I could just let it run its course...

jeffswav

When the E10 separates high octain ethanol with water is in the bottom and low octain gas is at the top. You pump the ethanol and water first then you pump the low octain gas. The boat runs like crap througout the entire tank but it runs different depending on witch part you are burrning. Mine ran like crap at first (ethanol and water mix), then it ran better when it was running the low octain fuel. But that was most likely when I ruined my berrings. I am not sure if this is your problem but I would be carfull with how you store your fuel.
Have you tried cleaning the fuel injectors like the other guys are talking about? I have heard of that causing problems also.
If you run it and you start hearing a screeching squeeling noise shut it down or you will do more damage. That would be the berrings failing. I hope you do not have this problem.

stereoman405

Very interesting. Well no squeals yet, but I'll be very diligent in keeping an eye on things. I'm heading up tonight with some B12, a new fuel pressure guage, and an entire tune up kit. Hopefully I'll be able to nail it down by tomorrow afternoon. I also found a Mechanic up there with a Merc scan toll so hopefully if I can't figure it out that will shed some light on things.

Thanks for all the help. If anyone thinks of anything else please let me know.

johnlaskowski

On my 502s the injectors are under the plenum and each injector has an individual filter. my motors just started running like crap one day all of a sudden. all the crud that was in mine had come about from the boat sitting the long 6 months at least in storage a year for the winter. so it is possible for them to be plugged exspecialy with the poor quality of fuel we have now a days and the higher cleaning agents that are put in all fuel for better fuel mileage. Alos as said before at 1/8 tank your pretty much sucking all the crud off the bottem.

Griff

Most boats will not even stay running and get on plane with less than 5 gallons of fuel in the tank. The fuel sloshes around and the fuel pump sucks air.

stereoman405

Well after more diagnosis, I put a gauge on the rail and it stays at a solid 38-40 PSI. (Supposed to be 43 but I imagine my cheap MAC Tools guage might be a bit off.) When the problem occurs the pressure drops to 5-10 PSI until I back off throttle for a few seconds, then it clears right up. (Its been in the upper 80's up here.)

What's interesting is that the issue is definitely temperature sensative. If the cover is closed I can get it to act up right away. Cover all the way open, hard to get it to do a thing, partially open with blower on it can go 15+ minutes @ 3000rpm's, but only 1-2 minutes @ WOT. So it seems to me it is a definite vapor lock issue or high pressure pump failing.

I made sure the cool fuel setup wasn't clogged on the water side, and picked up an entire new unit I havn't had time to install yet.

I just wanted to see if the new symptoms points into anything else before I put in the $350 pump.

2Slow4me

Double check all your plugs.

I has simlar issues (carbed boat) and a few of my plugs where cracked, hairline tiny cracks...

why or how, no clue.

But that did resolve the issue.

P.S. Having the issues again, so will be checking mine on Monday as well.