5.0 MPI with power loss, stalling at 3,000+ RPM

[gwebs]

Hello Everyone,

I am new to this forum and would like to solicit some collective wisdom on an issue I am trying to solve.

I have a 'new to me' 2002 Sea Ray 260 with a 5.0 MPI/Bravo III that I bought a month or so ago. It ran fine during the sea trial. It had 1/2 a tank of 'last years' gas in it at the time of purchase. Rev'ed up to 4,300 RPM during the survey, the surveyor commented that he would have 'liked to see 4,800, but that it was 'okay''.

It ran fine the first few times I had it out. However, it developed this issue where the 'engine guardian' would kick in and drop me back to idle as I approached 3,000 RPM. It happened 3 times in a row, so I idled back to the dock. I didn't know it was the 'engine guardian' until I got back to the dock and read the manual. I don't recall if it beeped then, there were no alarms at idle speed. It beeps at startup.

I thought maybe I had clogged the intakes. But, for good measure I replaced the fuel/water separator and the 10 micon inline fuel filter, since I had no idea the last time they were replaced.

It ran fine the next time I had it out. However, the time after that it would stall at around 3,200 RPM just as it came up on plane or slight after. No alarms other than a single beep. No engine guardian. It had no trouble restarting, but there was a few second delay from when it would stall to when it would like me crack it. I.e. - after we had stopped I turned the key and nothing happened for a few seconds.

Suspecting bad fuel and/or clogged fuel injectors I pumped out the remaining fuel in the tank and replaced with fresh fuel and a dose of quicksilver injector cleaner and some stabil 360. I let the engine idle for 50 minutes with this mixture and then shut it off for the night.

The next day I took it out -- it took a lot of throttle to get up on plane - like it had lost some horse power. The tach said 3200 and we were barely doing 20 mph and barely on plane. I had come to expect closer to 26-27 at this engine speed. When I advanced the throttle faster it didn't pick up much speed and I started to feel a vibration -- which is a new symptom. I went as high as 3600 before I pulled it back, because clearly something was wrong. But it didn't stall!

Did I give the injector cleaner long enough to do the job?

I think the next thing to inspect is the ignition system: wires, contacts, plugs, distributor. Is there anywhere else that I should look?

Thanks,
Greg

 

[scoflaw]

Full tune up. Just don't look at those parts, replace them, wires too. Do a compression test while the plugs are out. Your surveyor didn't do you any favors, he shouldn't have let that 4300 rpm slide..

Obviously, bottom clean, props decent. If that don't fix it, check your fuel pressure. Probably a T bolt 5 ignition. ignition module could also cause this, but first things first.

 

[gwebs]

Update --

I replaced the plugs and wires but it did not solve the issue. At WOT it was barely turning at 4,000 RPM and cruising around 20 MPH according to the speedometer and GPS. I did not replace the cap and rotor yet. I did not check the compression.

A few questions that I hope you can help with:

1. I looked for the fuel tank vent to see if it was blocked, thinking that could lead to a 'starving for fuel' situation but I could not find it. On the tank aft there are two fittings, one is the uptake tube the other is blocked off. Forward on the tank (harder to get to) are two hoses that both go to under the gas cap. It seems that one is a vent hose, but it is shut off to the outside when the gas cap is closed. Should there be another vent on the tank?

2. I also traced the positive battery cable to the starter and found where the coil connector is. I wiggled it and found that it could move easily. Like it was on a swivel. I hesitated to tighten it because it looked like it was made to swivel. Below is a link to a picture. Is this correct?

https://drive.google.com/open?id=0BxV4JdsLubYkaDVSTXRuc191czQ


I plan to check the fuel rail pressure later this week. It didn't stall at high RPM this weekend, but it did stall once while idling back to the dock.

Engine Model: MCM 5.0 MPI
Engine Serial Number is: 0M341681

Thanks.

Full tune up. Just don't look at those parts, replace them, wires too. Do a compression test while the plugs are out. Your surveyor didn't do you any favors, he shouldn't have let that 4300 rpm slide..

Obviously, bottom clean, props decent. If that don't fix it, check your fuel pressure. Probably a T bolt 5 ignition. ignition module could also cause this, but first things first.

 

[cgschaefer]

Hi Greg

I purchased a 2002 260DA with the 5.0 MPI B3 about the same time as you. I don't have an answer for you because I'm just learning the boat, too. Long-time sailors but first time power boat owners. I have a similar but not identical situation. Occasionally, when I accelerate out of the hole, the engine will hesitate. You can feel it but you can't hear it. No discernible drop in RPM's on the gauge and oil pressure and engine temps are normal. I can still get to wide open throttle (4800 - 5200 RPM; tach seems to move a bit but I think 4600 - 4800 RPM is normal for this combo) and I can cruise at 24-26 mph at 3800 - 4000 RPM all day long. But the hesitation, or minor surges, really bothers me. Like you, we've replaced the gas with fresh gas; sent the injectors out for cleaning; replaced fuel filters and oil. Have not done a complete tuneup, though. I guess that is next. Both batteries are fine. Let me know what you uncover. Our symptoms are different but they are similar enough that I wonder if we have the same issue.

Carl


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[cgschaefer]

Hi Greg

I purchased a 2002 260DA with the 5.0 MPI B3 about the same time as you. I don't have an answer for you because I'm just learning the boat, too. Long-time sailors but first time power boat owners. I have a similar but not identical situation. Occasionally, when I accelerate out of the hole, the engine will hesitate. You can feel it but you can't hear it. No discernible drop in RPM's on the gauge and oil pressure and engine temps are normal. I can still get to wide open throttle (4800 - 5200 RPM; tach seems to move a bit but I think 4600 - 4800 RPM is normal for this combo) and I can cruise at 24-26 mph at 3800 - 4000 RPM all day long. But the hesitation, or minor surges, really bothers me. Like you, we've replaced the gas with fresh gas; sent the injectors out for cleaning; replaced fuel filters and oil. Have not done a complete tuneup, though. I guess that is next. Both batteries are fine. Let me know what you uncover. Our symptoms are different but they are similar enough that I wonder if we have the same issue.

Carl


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A few weeks ago, we had the marina techs replace the distributor cap, rotor, and plugs. Essentially a tuneup except that we did not replace the plug wires. The cap and rotor were pretty corroded. The tuneup cleared up our problem.


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