My Boat is a 2005 Fountain 35 with twin 525s, serial # OM951038 & ...40. All gauges reading normal, when I came off plane after running around 3200 - 3500 rpm for 20 minutes in rough water. I idled for about 30 seconds and shifted both drives into neutral when a steady alarm sounded and both warning light lit up (I assume indicating both engines). Of note was the shifting to neutral was harder than normal, usually it shifts smoothly. I quickly turned off both engines and checked the drive lube reservoir (both full) and drives to confirm no obstruction to water intake (eg plastic bag). I started the engines a few minutes later and returned to the marina where no further issues found, plus drives shifted smoothly as usual. I had replaced both IACs 3 years ago after multiple beep alarms and have had no alarm since then. I spoke with a service tech who surmised my throttles may not have been all he way back, or the idle was higher than normal adding to the hard sifting and possibly alarm. My plan is to continue to run the boat until the end of the season which is late September for me and have the tech scan the engine then, unless I get more alarms. I just wanted to find out if anyone here has had similar issues and what you learned from it. Thanks Greg

I had a MAP sensor act like that. Was intermittent and tough to catch with the scan tool. After I installed the smartcaft display though, I didn’t take long to reappear and catch.

Pretty sure a steady alarm is overheat.

That’s what I thought when the alarm went off, that I had picked up a plastic bag in the water but couldn’t find anything. Also, water pressure and coolant temperature were normal when I started up the engines within a few minutes. I did kill the engines as soon as the alarm went off, so it didn’t sound for long, but I’m sure it was a steady ring as opposed to the multiple beeps when my IACs were going bad.

I also heard a (one) muffled pop from the engine compartment or exhaust, possibly a backfire when I shut the engine off.