Mercruiser 350 - 2 beeps every minute

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CaptTom

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3441
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Engine: 2003 Mercruiser 350 Mag MPI.

Engine will run all day at low speeds. Get on a plane, and within 10 minutes I get two loud "beep" engine alarms every minute.

Temperature, oil pressure, and everything else looks fine according to both the gauges, and the SmartCraft monitor.

My regular mechanic's engine computer code reader doesn't work with this engine, and the other nearby shop can't get to this for a few weeks. Previous Google search did not turn up any one thing, others have had reported similar problems and ended up replacing different sensors.

Any suggestions would be welcome at this point.

Thank you!

- Tom
 
if its a mercruiser with a bravo 3,did you check your outdrive fluid level
 
Yes, it's a BIII, and yes, outdrive fluid level is at "full". It was a little down (but above "fill") when this started, but I topped it off the first time it happened. I figured that was it - until it kept happening.

Funny thing is, it only happens at high speed. I've done probably 40 hours below planing speed, no beeps. Bring it up on plane for 10 minutes, the beeps start. Back to low speed, they continue until I shut off & restart the engine. Then no beeps until I'm up on plane again.

The mechanic who usually works at our marina apparently doesn't have the right reader, the guy who does has a 2-week backlog of work. I'd like to be underway on vaca in 2 weeks. At this point I'm ready to randomly change out parts, if only I knew which ones to try.
 
2 bp/min means that you most likely have a sensor failure. If there was an overheat/oil pressure problem, the alarm would be constant and not beeping.

Among the possible sensors which could be open/shorted are ECT, EST, Fuel injector, IAC, knock sensor, MAP, oil CKT, TPS, Sea Pump CKT, 5VDC bus power, MAT. A scan tool will tell you which one for sure.

A good place to start would be to check all of your harness connectors and make sure that they are seated properly.
 
That doesn't narrow it down much, but I appreciate the input. I suppose all I can do now is check connectors until I can get someone with a scan tool down to the boat. It's frustrating that they didn't build this into the SmartCraft gauge/monitor that I spent extra on so I'd be able to monitor the engine!

I was hoping someone who had the same issue might have directed me to the offending sensor, but I suppose it could be any.
 
Thanks CurrentSea, sounds like the MAP sensor is the one to start with, but I don't see in that thread where there ever was any resolution. Very frustrating!
 
I had the 2 beeps a minute problem twice on my 2004 350 MAG MPI. Both times it was the Idle Air Control Valve. I always keep an extra on board. It's easy to replace. Apparently they don't last very long.
 
Thanks, that's a good tip. It's going in to the shop tomorrow for analysis, I'll post back here when I know what they found. Meanwhile, I'll look up that Idle Air Control Valve part number!
 
kellyr, have you replaced the IAC mufflers? I have found that many IAC failures are due to clogged mufflers which restrict the airfow and cause the IAC to run at a very high duty cycle which overheats and damages them.
 
IAC muffler replacement? I don't know. I'll ask my mechanic about that the next time I see him.

All I know is that less than a year after owning the boat the 2 beeps a minute alarm starts happening. The boat was under warrantee but I still ended up paying over $300 in extra labor because the mercury certified mechanics took 4 hours to diagnose that the IAC was the problem. Apparently they have the computer diagnostic equipment too. My first impression of "smartcraft" was that it wasn't very smart.

After the same problem happened the next year, I had my mechanic show me where the IAC is and I ordered an extra one just in case.

I have had several other boating friends have problems with the same part. We are all in Florida.
 
A surprising number of techs I talk to say "IAC Muffler??? Never heard of it". It's not mentioned in any Merc service manual, but trust me, it's there (in the throttle body) and when resrticted can cause low, rich and unstable idle and will cause premature IAC failure.
 
Boy, Dave, if this were the 1st day of April that sure would be one hard sell. However, I know what you are describing and even just saw pics of them you have posted elsewhere. They're real! ( and they don't have bearings.) :D It's just a little square-ish piece of foam at the IAC inlet in the side of throttle body. New -white/ dirty-black. Looks washable and only about $.87(discounted + $$ shipping?) to replace a $.005 piece of material. You noted if the muffler is dirty the IAC may cause rich idle as well, and if missing the IAC may buzz a bit.
 
The answer is in!

We don't have a winner, but we do have one runner-up.

The problem was....

Shift Indicator Switch.

Runner up... Kellyr66

While in there, the mechanic found that the Idle Air Contrl Valve Muffler was badly clogged.

Thanks to all our contestants. You'll be going home with a BoaterEd board game so you can play along at home!
 
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