Weird 525EFI Question
 

So , idling out of Stonington harbor , hear a "pop" . Raise hatch , do the once over , everything looks good. Get underway , port side won't pull rpm , like timing isn't advancing or starving for fuel. All gauges perfect , sounds strong at idle. Changed fuel and sep. filters , plugs , plugs not rusty . Ran out of light for test run so ?? Anyone suffered these symptoms? Bummin!!

Compression test and cylinder leak down results?

can you explain the pop, back fire, ?? something broke ?? sounds like it may of went into guardian mode

No test results , had comp tester but worked late and not enough time til dark . Planning on quickie run tomorrow afternoon to prob find out my issue is deeper than I hope . Possible electrical ? No warning beeps , sounds flat , can get 4k rpm max trimmed to the moon.

Sounded like a muffled backfire . New to EFI and computer control , baffled . Thought of having ocean perf do a code scan but have no warning beeps. To me it seems electrical but that could be me hoping for the bast!

Just caught your guardian mode comment , thought that initially , have the manual but couldn't seem to find anything in the manual about the guardian mode. Of course , I left the manual in the boat when I left the marina.

I would have it scanned it might point to something that's not setting off an alarm, what your feeling ( no power ) is symptom's of guardian mode the ECM is trying to keep it from damaging the engine, and you said it sounds fine at idle ??

Going to call in the morning . Should have called already , looks like a lost weekend. Thanks for the second opinion!

hopefully not all lost, good luck

If the engine still revs ok not under load (in neutral) good chance you have a vacuum leak from probably a hose that came off somewhere. Check for vacuum small hoses that
that would change the timing. Sounds like what happen to me once. Even had my mechanic in the boat and he could not figure it out. A friend found it. Small 1/8 vacuum line under the whipple charger in the manifold. It was effecting the timing through the ECU. It would rev up fine in neutral but once we tried to get on plane it would lay down. Not 525's but sounds the same

Will definitely be looking for that tomorrow! Thanks for the lead! Fingers crossed ! Seemed to run up normally until the low water pressure beep at about 4000 rpm in neutral on the lift with the lowers dipped in the water . At least I am assuming that's what's the beep was . Have heard it before when getting too excited revving them up on the lift.

Bripar77 may be on the right track. Backfire may have blown hose off fuel regulator. Hopefully nothing internal. Good Luck!!!

Have a scan done. On our 525s once in awhile starboard would make a metallic tap sound while getting on plane only. Sounded like it was in the exhaust header. The tap would only make the noise one or 2 times when getting on plane, otherwise engine performed fine. Turned out it was a bad cam sensor.

I had the same problem once, it was that the mechanic's fault by putting the number 5 plug lead into the 7 and vice versa. Idle was fine, no power and it did backfire.

If the wires were swapped it was not fine at idle. There is a pretty distinct vibration to a misfiring engine.

Believe me it did idle fine, and that was one of the reasons I took quite a while to solve the problem. but it use to backfire also on idle

I had a 500 EFI that had the same simptons .turned out it was the coil pickup that is under the distributor cap.You have to pull the dist.and knock the pin out of the gear and slide the shaft out to get to it.I to replaced everything else till someone mentioned it here on OSO.Just a thought

525 doesn't use a distributor like a 500, they have a cam sensor.

So the plastic cover where the distributor would normally be is the cam position sensor ? Really appreciate everyones input !

Yes sir, bring a fuel pressure gauge when you go to do the compression test

not all the time..have seen wires crossed and idled just fine, but would pop and no power...just depends which wires are crossed...

Plug wires are on correctly , just started acting up out of nowhere . Ocean Perf says no beeps equal no codes . They wont come to my marina to read codes , have to bring the boat to them , kind of disappointed with that. I didn't mention that the engines are at 310 hours , so that may open up a bunch of other possibilities. They had the "200 hour service " but original top ends . Leaving work soon to go mess with it some more .Might be haul out time . Thanks for all the advice !!

Did not read the whole thread here but what about valve springs and checking spring pressures ? I would take a fuel pressure gauge and leakdown tester to add on top of the compression testing. Also any water reversion or water leaks finding its way internally into the cylinders

BUP- clean your pm's

No one thinks cam or crank sensor ?

If fuel pressure checks out and theres nothing obvious wrong thats where I would be looking next.

It is time for a top end refresh, but I dont think the springs are bad enough to not run over 4000 RPM's and make the motor sound flat.

Just saying start with the basics, fuel pressure, comp and leak down, check all 8 for spark (inline sealed spark checkers) plus read your spark plugs closely and take fuel samples and or what is the condition of the fuel that is running thru your motor.

Also the real first basic steps to try and receive help for fixing any marine engine is to post what exactly you have.

OEM stock motor or NO

year model

Engine serial #.

This basic info sure would help a bunch. Plus it helps any factory tech look up Service bulletins that might be the fix for any motor .

bck - you or anyone can email me at

[email protected]

Please put a subject matter in the email for example from - OSO- boat or parts or what ever marine related so I open it up. Thanks and I will look for email.

Update. Checked spark and compression , 150lbs comp. on all 8 and good strong spark. Bup , I think you nailed it . After changing plugs and filters and treating the fuel , all is well again , had a great test run . I think I dodged the bullet. Think I got bad fuel. Heard thru the local grapevine that the marina I fuel at was trying to empty there tank for replacement and I fueled up toward the bottom and filled port side tank last. Thanks to all who offered advise , you guys are awesome ! Heading to Greenport ,Long island for maritime festival in about 2 hours.
Bill

So how do you get around bad fuel without fully removing it and add in new fresh ?
No potion can do that.

Edit in: Glad to see it's running normal again and you can go have some fun.

Changed all filters, added dry gas , purged fuel lines . So far so good .

Old and or bad fuel can set your knock sensor faults so look for them while scanning the motor especially running it. Also IMO I think you might had some water in the gas and run it thru the engine. That's why I posted condition of the fuel ?

Also RVP of the fuel itself. RVP = REID VAPOR PRESSURE can fool the best tech in the world trying to pin point engine problems. Fuel for many years has different blends for the changing seasons especially in the North and here in Texas.

Winter blended fuel is totally different than hot summer blended fuel because they have different RVP values. There is RVP testers out on the market if your a serious tuner / mechanic / drag racer along with specific gravity testers for fuel.

A lot of Tuners like for example NHRA Pro Stock engines will test the fuel blends that day at the track to fine tune their air / fuel mixtures thru out the day and changing weather conditions thru out the day. Also as fuel sits it loses its octane rating and has better chances of collecting water even non ethanol gas will collect water in a boat from condensation off the top of the inside gas tank. All boats persay have open fuel vent system which also can lead to condensation build up in the fuel tank.