Happy 4th! Not. Engine restricting RPMs...?

[limitedwave@gmail.com]

So yesterday afternoon on the 3rd, after a normal evening the night before, and a normal morning of minor cruising here and there, all of the sudden - problems. As I came to an idle, and was about to throttle forward just a little, the engine puttered out quietly. No alarm or anything, just turned itself off. It continued to do this for a few attempts. She starts like normal, up to 1200RPM, and dies instantly, quietly, no alarm.

Three hours later, she starts and runs a little. 3/4 throttle only gets 1200-1500 rpms so we know there's a big problem. As we're puttering back to the marina at no wake speeds, it seems as though we've broken through the sputtering, and even get back on plane briefly. The fuel flow seems to sputter out again, and we're back riding at idle the duration of the trip back to the dock.

It seems like its running in the "safe mode" the book talks about (it had a cooler name for it). My oil levels are maintained, the coolant reservoir is just under half full. The running temperature on the thermostat is 160-170, oil pressure is right in the middle. This boat was just purchased 4-5 weeks ago and had a clean bill of health from Marine Max.

Any ideas? I bet this is the only post on a forum today. I sincerely hope all you others are not so typically unlucky as us!

 

[flflatrate]

start with checking fuel pressure

 

[limitedwave@gmail.com]

How do I check that?

 

[limitedwave@gmail.com]

...and I can rule out the Guardian Strategy system, since it would yield an alarm and I'm not hearing one.

I've been reading the Merc troubleshooting guide here and I'm thinking it could be throttle/fuel system related. Or an EFI problem. The fuel lines all looked good, maybe fuel filters? Maybe bad fuel...but I ran off a quarter tank of the new fuel before problems started. Maybe there's a problem in the throttle cable. While resting in a 1/2 full position the speed would increase and decrease randomly. Hmmm.

Thx btw...I'm just trying to troubleshoot ahead of time. It'll be expensive for me to get a mechanic out to the marina so I want to ensure no time is wasted!

 

[limitedwave@gmail.com]

Update: first attempt at changing the fuel filter unsuccessful! I have a new filter ready and waiting, the old filter was far more difficult to remove than expected. I'll try again tonight with proper tools. I'm becoming quite certain there will be some nasty water found in the old filter. I don't know what else it could be.

 

[Nehalennia]

Ask MM what all of the common symptoms of a bad IAC (idle air controller) are. I've had mine replaced after having a high idle issue, but it revved up fine. I believe there are many other symptoms however of a bad IAC.
A new fuel filter won't hurt anything certainly.
Best of luck.

 

[limitedwave@gmail.com]

Well it isn't the fuel filter. Replaced it twice, no change. Boat comes out and gets checked out Thursday. Can't say I didn't try!

 

[Steve04]

which fuel filter did you replace the spin on, or the inline? my 34 has two filters the inlines ones run from tanks to spin on. also do you have fuel injectors or carbutor? it could be the high speed jets, ethanol does wonders to carbs.
steve04

 

[limitedwave@gmail.com]

My boat got pulled today, and *fingers crossed* will actually get looked at tomorrow. It seems like a fuel issue. When in gear and throttled it misfires and chokes all over the place. Also curious is the fact that there are like 30 boats in my marina having fuel problems right now, most attributing to ethanol in the gas. My problems could be anywhere in there...fuel pump, injectors, screens, no telling.

Mechanic called me today and said "you know it could be anything...she idles just fine...". I hate when those guys say things like that. It actually couldn't be anything. Its most likely one of a few things and if it isn't, many smart people will be very surprised.