95 malibu echelon dying after warmed up

[Montanaechelon]

Hello all,

I'm new to boats and just got a 95 malibu echelon with the mercruiser 350 EFI 2 months ago.  The boat was owned by a military mechanic and appeared to be in great shape when I bought it. We did a water test and everything seemed great.  I started taking it out on the water as it's warmed up about 2 weeks ago and have started running in to some problems that I am hoping I can get help with. 

 

When we first put on we have a solid 1-2 hours where the boat runs like a top. I have been out with a few friends who have a lot of experience with 90's direct drives and they have been happy with how the boat was running.  The first day out it was high 70's and after 2 hours when I was towing my kids on a tube at 10-12 mph the boat died.  It didn't sputter or misfire just cut out.  I propped open the doghouse and after 30 minutes or so it ran a little rough for a few minutes then ran just fine until it died as I was pulling into the dock.  The next 3-4 times we ran out for under 90 minutes and didn't have any issues, pulled skiers just fine but we didn't pull the tube.  After that I went out and after 2 hours of cruising and skiing I blew up the tube and the engine cut out again, it started up a bit rough after 20 minutes of trying to crank it but would die if I tried to get above idle, once I let it idle for 5 minutes it ran just fine, until it did the exact same thing when I got the tube back out so we cooled it down again and went back in.  Initially I thought it was bad fuel so I ran through a full tank of non ethanol and added a few cans of sea foam, then I took it out for a run without the tube and the same stalling issues are coming back.  

 

I have a slot with the local malibu dealer next month but don't want to waste my whole summer.  I'm not the most mechanical but none of the stuff I have looked into seems all that complicated. My initial thought is that I'm probably dealing with an electrical issue since it's cutting out once things heat up and isn't sputtering to a stop. My plan was to try and swap out the ignition coil, water separator fuel filter and the impeller but I am having trouble figuring out which parts I need to get.  

 

If anyone has any advice on how to troubleshoot these stalling issues or best ways to track down parts that would be much appreciated. 

[REHinH20]

Are there any alarm sounds when this starts?  You mention letting it cool off, do you mean literally watching the temp gauge and waiting for a certain number, or just mean giving it time.  If watching the gauge what temp does it show when this starts to happen?

[Montanaechelon]

No alarm sounds when the boat stops.  I just give it time, try to crank it over every minute or two and feather the throttle with the boat in neutral until it finally turns over.  

[Rednucleus]

Coil or ICM are both heat sensitive parts. Fuel filter & impeller are fine to change if it's time, but I doubt they will fix the problem.

[justgary]

3 hours ago, Montanaechelon said:

feather the throttle with the boat in neutral

Absolutely no need to do this for an injected engine.  Turn the key; it should start and run.  Is it multiport injected, or throttle body injected?

First, make sure that your safety lanyard switch isn't winking out.  You can bypass it with a short wire on the terminals behind the dash.

Test the fuel pressure at key on, idle, and wide open throttle.  They should all be the same.  If they are not all about 44 PSI (need to verify that for your engine), you have a fuel problem.

You should be able to watch the spark advance with a timing light to make sure it is smooth with RPM.  If it is jumpy or disappears when the engine dies, you have a spark problem.

I do agree with @Rednucleus that the ICM in particular is a heat-sensitive part.  I just learned recently that they aren't $20 anymore though, so it might pay to diagnose some more before just changing it.

[Montanaechelon]

Is a way that you recommend to check fuel pressure? I haven't ever had to replace fuel lines or a fuel pump but I'm sure it can't be that difficult. I have seen in line fuel pressure gauges, is that something you recommend just plumbing in to a fuel line or is there a simpler way to go about this?

[Montanaechelon]

Also if it's helpful the engine is a 350 magnum EFI tournament ski serial number 0F351931.

[Steve B.]

Think I had the same engine. The fuel pump is the huge thing bolted on the front starboard side? With a water separator attached? 

Steve B.

[Montanaechelon]

45 minutes ago, Steve B. said:

Think I had the same engine. The fuel pump is the huge thing bolted on the front starboard side? With a water separator attached? 

Steve B.

That’s the one. Do you remember if yours had a valve on the fuel rail to check fuel pressure? I can’t find one on mine. 

[Steve B.]

Hmm, ha. I can't remember. It's throttle body injection. There may have been a way at the pump to check, but I don't think there are rails to tap off of. My engine came with a manual, and for some reason I want to say that if the pump had run dry, etc., that it needed primed after some fuel events. As I recall there may have been a nut at the top of the pump that you could back-off and let air release? This was a long time ago, so I may be way off. The reason I remember this is these are prone to vapor lock, and a quick fix was to bleed the vaporized gas by un-screwing that bolt and letting gas escape until fuel came out.

Anyway, manuals for this engine should still be available online. They may be of more help.

 

[CrystalLaker]

I was just saw your post and was wondering if you figured this out?  I have a 1995 Response with a 350 magnum EFI and had a similar problem years ago.  The boat would run perfect during the first runs of the day.  However when going back out after a break it would crank, pull up a skier (or whatever) go about 400 yards and die. After about 30 minutes it would crank again and run fine. I found that if I opened the motor box when I came in for a break I didn't have a problem when I headed back out.  

After doing this for a while I decided to read my manual, and started using non ethanol gas as it suggested.  No problems since.  My guess is as the motor compartment heated up from sitting rather running, the ethanol fuel was causing vapor lock.