Engine Alarm constant over 4500 rpm
 

Did the shore dreams for kids today on my second run I started getting a constant alarm over 4500 rpm.And two shorts beeps every few minutes under 4500Rpm.It is not getting hot 175-180 and have plenty of oil pressure.The alarm is on the starboard engine.That engine also requires about an inch of throttle movement to stay running it stalls if throttles are all the way down.Will scan it tomorrow to see if there are any codes.All my fluid levels are fine and there appears to be plenty of water coming out of the exhaust.
Any ideas?

Tim, My brothers 271 fast tech did the same exact thing last year did it a bunch of times and we could never find out why and it just stopped all by itself. If you figure it out let me know we tried everything even ran computer diaignostics and came up with zip. good luck

The reservoir is full,wouldn't it take from there if the drive was low?

Scan tool will tell you the code. There are so many sensors that set off the alarm that you have to use it unless it is low drive oil(90% of beeper problems)If drive oil is ok,scan tool will tell you.We had a shift position switch go bad last week,told the ecm that drive was jumping out of gear. It wasn't,but ecm thought it was. But if engine is not going into guardian mode,then like the previous post,I suspect drive oil.Low drive oil triggers the beeper,but not guardian mode.

Am I correct that if the reservoir is full then its ok or am I missing something.Also it won't idle with throttle all the way down.Thanks Tim

Just got a call from a friend and tech guy,he said IAC(Idle air control)He said same symptoms on 3 boats recently,IAC solved it.I trust what he tells me.The IAC is not very expensive and easy to change out.

Thanks will see if I have a code tomorrow,will let you know

I had same symptoms on my 292 with 6.2's. It was a bad IAC. Tech told me it is a very common problem with those engines. Heat from the engine cooks them. Very simple to change. Just take off top engine shroud and its right there. Will need the gasket too, if that is your problem. Later that same weekend, lost a water pump impeller. That was enough problems for one weekend. Changed both water pump impellers just for good measures.

IAC or TPS makes sence but we could not get any codes on the 271 w/496HO and the problem went away by it self

I assume you'r running 496's.. I had similar (but not identical) problems, Check you fuel pumps. oth HP and Lp. THere is a screen/filetr front of the lines. They canget clauged up, not enough or wrong fuel, sensors go nuts.

Yes.....IAC. You're in a soft alarm. 2 beeps per minute tells you it's a soft non-critial issue. At 4500 it goes into a soft guardian mode reducing your avaialable horsepower down to 90% and the alrm goes constant until you back it down to 1100 rpm where it goes back to the 2 beep deal. Rough idle is another indicator i.e. IDLE air control.

It's located looking aft, on the top rear of the motor near the throttle linkage mount. Kinda looks like a little thermostat. Two allen wrench type screws holds it on and a electrical connector. Simple, somewhat cheap and easy.

Tell your friend its 4 boats in a row installed a new one this morning and its is now running great.Thanks to everyone for your help Tim

Tim, did it set any codes? I would really like to know because we still don't know what was up with the 271

Never used the scan tool,The guy who owns the marina was not around so I just put on a new one.If yours does it again I would just change it

Thanks, Never has done it again but we will be look'n for it. Glad it was an easy fix for ya. By the way whatever happened with Micky Ds ?

If you have a Smartcraft engine, sometimes a bad IAC sounds the beeper, but a code does not always come up. I have also seen bad senders for the sea water pump pressure. The scan tool said it had 62 Lbs. at idle. No way a hose clamp could hold pressure like that or the hose not blowing up like a balloon.

Wish I had seen this thread a week ago. Had the exact same symptoms, and my marina shop chased the gremlin for a couple of hours before swapping the (good) starboard IAC to the (bad) portside. Viola! Problem solved, one new IAC for the portside and I'm back on the water.

Frustrating though, since I've only had about 5 days on the water this summer and was really looking forward to getting out that day. IAC problem hit the moment I splashed that day...

Its common for the 6.2s from what I have been told.I actually keep a spare with me.I got a lot of help from OSO and I also goggled the symptoms "engine alarm 6.2" went into a bunch of other boating forms.Which said IAC valve.

It's a real common problem on all the ECM/PCM555 engines. I believe that a lot of failures are caused by a restricted IAC muffler, which cause the IAC to run continuiously at 100% Duty Cycle and overheat.

Unbelievable. Port side IAC went bad on last trip out (4 weeks ago). Replaced it, all seemed fine until I went to do the 160 mile round trip to San Francisco Bay yesterday morning.

50 miles out the starboard engine started acting up in the same way, guardian mode, 2 beeps every 1 minute, etc. Had to limp home and am really p*ssed at myself for not replacing both IACs at the same time...:mad:

I will start carrying a spare on board.

I did the same thing I carry an extra one in my tool kit

Old thread different engine same problem.Constant alarm over 4000 rpms back off get the two beeps.
Before the season started did exhaust (Imco) new plugs impellers and thermostats.Good oil pressure running 170 where it always does and no codes.I am starting to think coil is breaking down or drive lube level sensor.
One weird thing though when boat was new the two inner baffles came out of the tips on the starboard engine so there is only one on each side.The port still has two and thats the engine that is throughing the alarm.I ask this because the Inco would not line up with the Y-pipes so I went strait through hull.Doubt small blocks with 4 inch exhaust could have a back pressure problem but I am at a loss right now.Might cut the baffles out tomorrow or just start throwing parts at it.Any thoughts?

I already changed the IAC

Weird....

Strange that the IAC fixed it last time you had the issue and not this time. Is this the one that was running hot at idle?

My memory is foggy and I can't remember if the drive lube switch opens or closes to sounds the alarm, I'm guessing closes.. You can always unplug the drive lube sensor and take a spin.

If you need anything let me know, I can make some calls.

Frank

No that was the other motor and I did both impellers and thats fixed.They sure are a lot easier to get to when the manifolds are off.It runs great just the alarm but no codes I had it scanned.Do you think it could be because there are two baffles in that motors exhaust?I doubt it but it is odd I don't even think the 6.2s have a water pressure switch.The other motor is a little louder now that its thru hull only.

I could be wrong but I can't see the exhaust being the cause unless the new hose routing is somehow effecting the cooling system sensors.

It's kinda hard to tell what it is. I'd have to check around with some of my buddies who are still in the business..I'm not current on some of this.

The new exhaust is run exactly as original used the same hoses just had to extend two.The other motor is fine.

The IAC is the most common failure but there may be an issue with crank sensor. On occasion the crank sensor plug in connector will get corroded from even slight circ pump leaks. The sensor is located at the 7 o clock position jsut behind the balancer. Corroded pins will not show up on the scan tool as it is triggering a signal, just not a strong one. They are pretty easy to change out. I would take them both out, check the connectors, clean them then swap them port for stbd. See if the problems moves to the other motor or goes away completely. i have on occasion bought brand new IAC's from merc that were faulty and expensive. NAPA has the IAC's and the crank sensors. They come off of a 2003 Lincoln Mark IV. The IAC cost is $28.00 and the crank sensor is $19.00

The 6.2's do have a water pressure switch. It is located in the top of the power steering cooler at the rear of the motor. I had one of these go so bad that the motor wouldn't start. The scan tool didn't pick up a fault either because it was stuck reading 39 LBS water pressure. NAPA and Advance Auto carry these as well but I would only buy them as a quick weekend fix. These have a steel housing not brass.

I did have a sea water pump leak on that motor last year its replaced now but it did drip for a few weeks.The Iac is new I had one but it idles fine.Is the crank sensor held on by a 7mm bolt like GM? At least I think thats what size it is its been a while since I changed one.
Thanks

Ok today
Took one baffles out of each port exhaust tips so the match starboard
Changed crank sensor
switched from port to starboard
water pressure switch
coil
map sensor
TPS
changed fuel filters
inspected cap and rotor little corrosion but not bad, cleaned

Still same problem I ran it WOT and let the alarm scream to see if it would get hot or loose oil pressure.It didn't Starboard motor will wind but port only goes to 3500 3600 and the alarm while mostly constant does go in and out.The tach flutters a little so it appears that I am loosing ignition or power to the ignition.I have a lot of water coming out of the exhaust and the impellers are new.Will run a fuel pressure check tomorrow but doubt thats it.I am about to condem the harness and it was changed last year.Thoughts????

Ignition wires?? can't see why that would throw an alarm I am guessing at this point.

Has it run good with no alarms after your new exhaust?

I you suggest leak down and compression test. Also a plug check and make sure the firing order is correct.

No but I did not run it this year with the old exhaust and the other motor is fine so I don't think its the exhaust.I checked the firing order three times its right.I did a fuel pressure check good motor was 55-60 other was 35.Changed regulator and it went up to 50.Ran it on a mercury box that replaces the boat wiring harness no alarm (because the alarm was bypassed) but still would not wind and got a little hot there were no numbers on the box gauge so I don't know how hot.I can use a Mercury computer tomorrow morning so see what happens.I have not done a compression or leakdown test yet but its the next thing after the computer.Starting to wonder if I hurt a motor but it runs and sounds great till 3500.Did a cylinder drop test by removing wires off the cap and got an RPM drop each time.Don't know but I am running out of things to check.Impeller is new but I could be loosing water pressure at high RPM but running stopped at 3k it seems to be the same coming out of the exhaust as the other motor.

try cleaning the grounds on that engine giving you trouble,,,

:cool-smiley-026::cool-smiley-026::party-smiley-020:


Fixed winded up being a shift selector switch I had it on a mercury computer this morning and it was going into guardian.Why it did not show up when I had someone else scan it I don't know but the ECM thought the port motor was in neutral and would throw it into guardian over 3500 if you held the throttle there.

Thanks to Southwicks Marina in Beach Haven NJ for all there help this weekend.The have 93 octane so if you need fuel stop by.

Good deal Tim, glad you got it all squared away and it wasn't a big deal to fix!!

Like I said on the phone, sorry I didn't suggest that, I just didn't think of it!:angry-smiley-038:

No problem every thing is easy once you find it.I can't believe I did not think of it either.Like the other thread with the 500s cutting out one guy said check the kill switches never would have thought of that.Thats one of the reasons we do theses threads is for the next guy