Alarm sounding and engine goes into Gaurdian mode at 3600rpms and above

[Mark72233]

Sorry for the long post.

A little back story. Bought the boat (October 2017) from brother in law who bought it new. Ran it a lot with no issues until around February 2018 when this problem started. Boat is a 2005 SeaRay 260 SunDancer with a Mercruiser ​

350MAG MPI, 300hp attached to a Bravo 3. ​

Serial number is OW345902. ​

When I take the boat out and run it past 3600 RPMs after about a minute or two alarm will sound and gives me a warning but no specific issue and goes into guardian mode. The alarm and guardian mode last until I bring it back to idle. The alarm is a continuous alarm, loud and steady. When the engine is cold this takes about 10 minutes until its warmed up and then it will happen. Once its warmed up to operating temp it does it in about a minute or less. ​

All the gauges are showing no issues. it has the analog gauges and the digital Smart Craft gauges and they both show the same info. Operating temp is 175*, Oil pressure at high rpms is 50-55psi lower rpms it will drop down to 25-30psi.​

I took it to my marina to see if they could figure it out and the first thing they tell me is their mechanic ran it and the temp went up to 195*, at that point I knew I screwed up because this boat never runs over about 175* even if I do everything you would do to an engine to make it over heat it never has. Needless to say he tells me my raw water pump needs to be replaced and parts and labor will be over a $1,000. I told him to stop where he was and bill me ($300) for the work they had done so far, which was removing and disassembling the raw water pump. The impeller was intact and I didn't really see the deep scoring he told me about. But to be on the safe side I bought a new pump and installed it along with a new belt and sure enough it didn't fix the alarm issue and the engine still runs at 175* like it always has.​

This problem started around February with no catalyst I can remember.​

Yesterday I changed the oil and oil filter, problem still there. ​

Checked the remote reservoir for the out drive and found it slammed full so I pulled some out down to the level it should be thinking maybe the alarm is that because in the past the reservoir ran a little low and the same type of alarm and guardian mode occurred except the Smart Craft gauge specifically read fluid level low in reservoir so that was easy to diagnosis and fix. Didn't fix it same problem occurred.​

Unplugged the wires from the oil pressure sensor. The main plug unplugged sounded a quick 2 beep alarm and wouldn't allow engine to rpm up so I don't think that was a fix. The other single wire unplugged didn't set off any alarms right away but didn't fix the problem once the engine went over 3600 rpms, alarm and guardian mode again.​

Then I started to see if alarm occurs at a certain rpm and sure enough I can run the engine all day at 3500rpms, no issues. Once I nudge the throttle and it runs over 3600rpms for 30 seconds or so Bam alarm and guardian mode. I literally ran around the bay at 3400-3550rpms for 30 minutes and no issues, bumped the throttle to 3650-3700rpm and 30 seconds later Bam, alarm. All the gauges reading everything within normal operating range.​

 

[Frankjl]

Hi Mark I wanted to hear if you found out what the problem was. i just bought a maxum 2700 with a mercuiser 5.0 mpi with bravo 3 from 2006
and it is doing the same problem at 3600 Rpm. best regads Frank