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57Gi cutting out dying at low RPM

centerisland

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"Obviously I'm a newbie he

"Obviously I'm a newbie here...I have a very specific problem that after 5 weeks at the local VP dealer, they can't fix. Partially in their defense, they admit up front they're a diesel shop.

My setup is a (new to me) 1994 Osprey with a 5.7Gi. Approximately 900 hours on the engine, though the previous owner said it's really like 650 because he left the key on all the time while trolling. I sort of believed him. He's an honest guy, but completely clueless about boats.

Anyway, starting with the sea trial, literally every time I return to the dock after running the boat it dies while maneuvering at idle. We're talking perhaps 12 trips of 1/2 hour each, crusing at 3,600 rpm with no problems. OK, one time it didn't die but that's probably because from coming off of a plane to getting tied up was around 30 seconds. More commonly, I'm navigating through a marina and maneuvering up to the dock.

More information...it always restarts quickly, and then doesn't die again. I recall that it's always in neutral, though it might have been in gear once. And once, while maeuvering to anchor at perhaps 1,000 rpm it stumbled, but didn't die.

A Volvo diagnostic code is a apparently not being thrown. I say apparently, because when they sea trial the boat after working on it, everything works fine for them! Un-freaking-believable, because it's a 100% repeatable failure for me.

Along the way they've changed the fuel filters, filled up with new gas, checked / tightened battery connections, done a tune-up (though they admit they're not gas engine experts), fixed a corroded connection to the fuel pump, and probably dinked with a bunch more things that they're not mentioning. And it still dies on me, every damn time.

I'm thinking of buying the Diacom software package from Rinda just so I can get more information, but I am not a mechanic and I really don't know where to start, or where to tell someone working on the boat to start.

Any ideas?"
 
"so, you are saying, this boat

"so, you are saying, this boat is dying at low rpms? Like no wake speed? Yes?
New fuel filter, new carb build, and new gas?"
 
"Yes, about 600 rpm. Zero wake

"Yes, about 600 rpm. Zero wake. Once while actually tying up at the dock.

Yes, new fuel filter (Racor S3227) and new gas, but no on the carb rebuild. FWIW, I _think_ this motor has "throttle-body injection"."
 
"Followup...if it helps...made

"Followup...if it helps...made two trips out today to set and retrieve crab pots (1 huge female, sigh). 600 to 1,100 rpm at most, maybe 5 minutes each way, idling over pots for a few minutes, limited maneuvering at dock. No problems.

It really seems that it's after a good run to get the temperature up. We haven't been running WOT, with the prop set on there tops is 4,000 rpm, but we've been running more like 3,600 to 3,700."
 
"My best guess: An electronic

"My best guess: An electronic component is dying on you from the heat. Why it comes right back, though....


Jeff"
 
"Another update...went out for

"Another update...went out for crab pots again this morning and spent longer idling around (couldn't find our 2nd pot). The good news is we had 4 7" male "keepers". The bad news is, I had the engine _almost_ die on me...it slowed down, and then came back to idle.

One thing I'd figured was that it might be temp related. So I ran this morning with the blower on, but it didn't help - I still had that interruption.

And more ideas? Anything more specific than "an electronic component"?"
 
"when was the last time that y

"when was the last time that you replaced the cap, rotor, wires and plugs.. I had a problem somewhat like what you are explaining and it turned out to be the cap and rotor.."
 
"something else you might chec

"something else you might check out is your cooling system(exhaust)make sure that you are not having a back pressure issue, I know that on the 5.7 mercruiser motor there are two flappers that are in the down pipes of the exhaust and if they aren't there, you take a chance of water going the wrong way.. ONLY A THOUGHT"
 
"Well, there was another mecha

"Well, there was another mechanic who was on the boat next to mine when the mechanics were working on my boat. He said that it didn't feel right to him, and to replace the wires and do tuneup. I need to follow up with the guys working on my boat and find out if they did replace these items.

The cooling restriction thing is interesting...my motor is fresh-water cooled...my gut feel is that this would mean that this wouldn't be a problem for me. Is that right?"
 
Something tells me You are loo

Something tells me You are loosing the electric fuel pump.
Did You properly fix the corroded connection?
Can You HEAR the fuel-pump run at idle?
If possible have a pressure test run at the fuelpump and monitor when the problem occur.
 
"Well...I didn't fix the c

"Well...I didn't fix the connection, but what was reported to me sounded reasonable. However...

Another long run...then running slow at 1,000 looking for our crab pots (1 went AWOL this weekend) and it cut out, then recovered. And today heading back to the marina, it died again. Thinking of this fuel pump question, I turned the key off, then back on (I always hear the pump prime) and I couldn't tell if it re-primed. But I had to adance the throttle a bit before it caught.

So...the heck with it...I'll just replace the damn fuel pump and wiring harness to it. How difficult is this? I honestly don't mind throwing money at this, but that hasn't gotten me anywhere and I'll just do it myself as long as it's straightforward."
 
"try the anti-siphone valve, i

"try the anti-siphone valve, i might be stuck. its only two dollars. alot cheaper and easier than the fuel pump."
 
"I did some googling on "a

"I did some googling on "anti-sphone valve", and it sounds like it's not part of the engine (my manual mentions a fuel meter, fuel pump, and fuel injector) but something that's somewhere in the fuel line, probably closer to the tank or perhaps around the external Racor filter. I'm familiar with these things on outboards...have used them to keep the kicker from pulling the gas out of the main...and you might be onto something here.

I don't have the boat in front of me, but will see it again in a couple of days. But I have a separate external filter for the T8 kicker, they're both drawing from the same tank, and there just has to be such a valve - or even 2 - in there somewhere.

As for how it would fail...I assume that we're talking about something that's keeping it from opening at low intake (fuel pump suction) pressure, right?"
 
"sounds like an idle air contr

"sounds like an idle air control selonoid, but hey what do i know. clean out your throttle body with a spray carb cleaner, on the port side of this you will see a larger hole in the casting side, also a 4 wire connector going to a selonoid in the side of the throttle body below the larger hole, clean up the carbon buildup down there and then go run it. may help, wont hurt."
 
"Well...I think it's been

"Well...I think it's been solved. There are two fuel pumps on the engine, and the one on the front was running hot. So they replaced it, and with 3 trips under my belt this weekend, it hasn't skipped a beat."
 
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