Conked out, wont keep running.

pstew96

pstew96

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Dec 4, 2003
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So, I have a new motor 2016, a 5.7 350hp Alpha EFI, I had experienced an alarm condition where it would put me in limp mode, but it only occurred at high RPM, I would throttle down and it would recover and as long as I didn't go past 5000rpm I was fine, so I got into the water and used a screw driver to make sure the intakes were clear as I checked all of my fluids and temperatures with a thermal gun and nothing was higher than 147 degrees. I thought maybe it was the intakes because my next trip didn't produce the alarm again, but then yesterday I took her out and coming back, the boat suddenly limped and stalled, I could start it again but it stalled again to the point where it wouldn't even run for a few seconds. Being I already blew one motor I wasn't in the mood to try for a second $12K motor so I called BoatUS for a tow, he suggested it could be an ethanol clogging issue, but I wasn't about to start the engine and rev it up, as I said, already blew one engine. I'm thinking I should change the filter and make sure I have fuel even though the filter only has about 150 hours on it. Or could it be something more nefarious?
 
The manufacturer's recommended WOT RPM range is 4600-5000, so maybe it's programmed to not let you over-rev.
 
quote:
Originally posted by GeorgeKohler

The manufacturer's recommended WOT RPM range is 4600-5000, so maybe it's programmed to not let you over-rev.

Click to expand...


If it was hitting a rev-limiter, I believe it should just not rev any higher than the limit RPM, ... not go into limp mode.

If the alarm sounded and a code was tripped , a marine scan device may help ID the code and cause.

But if no codes were tripped, I'd 1st check whether the fuel pump(s) run for a few seconds to prime when the key is just turned to On , not Start. If not, figure out why. The Serious Wiggle Test of the on-engine wiring harness with key to ON position may provide clues.
If any lanyard kill switch is present , is lanyard secured?
If pump runs, check for spark (the inductive pickup of a timing light can aid checking for ignition pulse) , contents of the fuel filter separators , condition of the dist cap if it has a distributor, and fuel pressure.
 
This only happens above 5K? Cuz it sounds like a temp issue. The higher the RPM, the higher the temp will go. I'm also not up on how the electronic limp and recover time factor works. I build my engines and keep everything as simple as possible so most problems can be fixed on board.

Also, what do you mean by 'Intake'?
 
My guess is he means he inserted a screwdriver in the water intake strainer to make sure it was clear.

If the max WOT RPM is 4600-5000, I would not run it beyond 3750 RPM for more than a test. The WOT rating is there so you can test to see if you can reach it with your prop. If you can't, you are over-propped. After running the test, you should reduce the RPM to the safe cruising RPM which is 75% of WOT. The range is there because if you can reach within that range, your prop is fine. If you can reach 5000 RPM and you know the engine has more to give, you are under-propped. If you keep operating that engine right at 5000 RPM, you will spend another $12k quickly.
 
Yes, it is 300HP not 350, and the WOT is between 4800-5200rpm. And yes, just to be safe I used a screwdriver to make sure the water intakes in the outdrive were clear. I only have about 150 hours on the newish motor. This time, when the thing stalled I didn't even get an alarm, I also noticed that my oil level was topped off two weeks ago, when I checked it 3 times Sunday it was at the ADD OIL level. But still, at that level I would either expect an alarm if nothing else. I'm going to check the filter tonight and the water separator. The EFI pump sounded a little strained but the few seconds was about the same amount of time.
 
I think you are running it at too high RPMs and it's going into Guardian mode.
 
I now find its all my bad, first the barnacles and crap grew thicker than they ever did so I got into the water and stuck a screw driver into the intake holes and I assume I cleared them as I couldn't see, I did it by feel. Now it seems to be ok, I am a bit afraid to open her up to much, I did blow the origional motor...
 
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