It's your water pressure sensor. I had the exact same problem with my port engine about a month ago (496HO engines). Put a new Water pressure sensor in and all is fine.

Well took it out yesterday and had no issues. Scanned codes when I got it back on the trailer just to see and everything was good with both.

So must be a bad connection, and the UN-plugging it and plugging it back in fixed it.

Re: 342, 496 mags, double beep alarm every 60 seconds, fault 37 ?

Well its been fine then this weekend, took it out, and ran 20 miles down river, no problems still. had dinner and fired up to go 1 mile to marnia, and damn alarm came back.....

the rest of the weekend its hit or miss weather it does it or not. Has to be the sensor.

interesting thread,as I have the same problem(s) with my 496

have to ask is your motor a 2002 model and what is your serial # ? being a true 2002 model your water pressure sensor is in your water pump Impeller housing correct ? If it is not and is in your power steering cooler then I might have the answer to your problem.

BUP...dont know if you're talking (writing?) to me, but since we're all in the same s**t with our 496,i feel im not hijacking anybody,as the info gathered here will help everyone....mine is an early model,with alum. exhaust manifolds...I'll get the S/N number tomorrow.... good luck with yours,Mittens

Really just need the location of your water pressure sensor and this can pertain to a lot ECM / PCM engines from Mercruiser no matter what model or hp. What I have learned about the water pressure sensor problem pertains to if it is installed in the cooler.

So, Got a new sensor, and was convinced it was just that. THEN, when running it the last time I had the alarm again, and assumed its just the sensor, scanned the motor and nothing.. .scanned the other one. and its now tripping low pressure.... SO its making me think its the impellers since they where replaced at the same time.

On the last trip of the season I ran back in with BOTH motors alarming every 60 seconds, they where 17 seconds out of sync... talk about annoying haha. BUT it made it though the season, and they are both getting new impellers. and I have 1 new sensor still on had in-case that's it.

My hope is the new impellers will fix the issues on both sides, and I have a new spare sensor. BUT if not then I will replace sensors next i guess.

Regarding impellers, I think they last a lot longer then most think. I changed my first one at around 300 hours. Still have it in perfect shape. Replaced pump a few years laterwhich came with new impeller. Existing one perfect shape. Last year installed Hardin pump that came with impeller, Existing one perfect shape. I have had 4 impellers in 12 years and over 750 hours and would re install any of the past 3. Not trying to stir up chit. In my opinion changing every year is overkill.

Do you have mechanical water pressure gauges? If so, what are they saying?

Do you have a Rinda (or similar) scanner where you can monitor the computer's reading of the water pressure, or just looking at the faults?
If you are looking at it though the RPM range while running, even a few hundred RPM difference on the hose should show different water pressure (goes up with RPM). If your sensor is not reading a change at all, it's the sensor, or a clog in it's plumbing.

There is plenty of talk about the pumps on these motors wearing out. IMHO, with it only being a $100-ish bucks for a while pump housing, it's worth swapping the whole thing, not just the impeller once in a while. Many people upgrade to Hardin SS pumps, but I think that's needed for people that seem to have chronic problems due to their boating area. Sea strainers also lengthens the life of SWP/impellers, obviously.

Also, the fresh water flush system that Baja factory installs is, IMHO, junk. It can gum up with sand/debris and cause low water pressure and overheating conditions. It has a spring loaded checkball setup in the Tee; and that whole spring/ball needs to ripped out and thrown away. It's not needed.