496HO Alarm Help

[SHEP]

I had a constant alarm on Saturday with our 496HO motor. Was cruising a light speed maybe 3600 RPMs and got the constant alarm and then it went into limp mode. Turned everything off and checked all the fluids and couldn't find anything wrong. After 5-10 minutes I started it back up and ran fun the remainder of the day. Bad sensor? Any other ideas?

Thanks,
SHEP

 

[Bpracing1127]

I had a water pressure sensor go bad one time that caused that

 

[kimbalee]

Ours did that once - was the sea pump.

 

[Badold65]

Where are you located? I can scan it for you if you're in Havasu.

 

[SHEP]

Where are you located? I can scan it for you if you're in Havasu.

That would be awesome. I won't be back out until Memorial day weekend. Not launching it that weekend but can bring it by if you're around for a scan.

Thanks!

 

[mjc]

That would be awesome. I won't be back out until Memorial day weekend. Not launching it that weekend but can bring it by if you're around for a scan.

Thanks!

if he can't scan it I can and I will be back saturday night.

 

[rivrrts429]

Low drive oil alarm?

 

[throttle]

As mentioned previously, ck all fluid levels, could be a heat exchanger or time for an impeller and or pump replacement. Worth a check up for a code and some re assurance for next trip.

 

[Singleton]

@SHEP
Attached the list of what it could be

 

[Chili Palmer]

I had the water pickup pipe from the outdrive through the transom corrode and cause an obstruction and the alarm would go off at any speed over 2800 rpm. BDMar Brian (RIP) installed a new pickup at the bottom right corner of the transom.

 

[CobraDave]

I just had a water pressure sensor do that to me on a different motor. $200 sensor though and don’t use Chinese knock offs. The parts guy also said sometimes the drive fluid sensor float thing will stick. Stick a rod in there to free it or replace it. Those were the two common problems he saw. Good luck. The water pressure sensor took five minutes and a wrench. I knew it was that because the boat would not overheat.

 

[spark2678]

As others have said, drive oil or water pressure. I have a scan tool, I am in the Islander and will be out Memorial.

 

[MK1MOD0]

Are there any low cost scan tools available for the Merc 496, 525 motors. Seems like it would be a great thing to keep on a boat.

 

[Justsomeguy]

As far as I can tell. The techmate pro is about as cheap as it gets. They also make a code reader that is flashing lights, that correlate to a code, that was cheap. I wasn't into that. I'm ordering the techmate. My alarm has been going off around the same rpm range. If anyone knows a more inexpensive option I'm all ears. I searched and saw an inmate just sold one in April. I was a bit late on that.

As one can see, it can be a few things. Scan tool is really is needed, and I figure it will be useful in the future I'm sure.

 

[shaffewm]

We had a chunk of plastic do that to us

 

[Mcob25rg]

I’ve had 4 496ho’s. You really need a scan tool - there’s around 23 DIFFERENT sensors on that thing. As a sidebar, there’s a screen filter in the bottom of the drive bottle mounted on the top of the motor. You can be looking at a full bottle, but the screen can get blocked / gummed up because of the heat - ask me how I know. You can easily remove the bottle, take everything apart, clean and install yourself - not really very hard. Not sayin this is your problem, but if it hasn’t been done, it will eventually get you - I decided to just add it to my 25 hour draining of the drive - one less thing to think about while you’re boating !!

 

[adam909]

Are there any low cost scan tools available for the Merc 496, 525 motors. Seems like it would be a great thing to keep on a boat.

mercury marine vessel view

 

[Shlbyntro]

Are there any low cost scan tools available for the Merc 496, 525 motors. Seems like it would be a great thing to keep on a boat.

I use diacom by rhinda

 

[rebelmark75]

I had a constant alarm on Saturday with our 496HO motor. Was cruising a light speed maybe 3600 RPMs and got the constant alarm and then it went into limp mode. Turned everything off and checked all the fluids and couldn't find anything wrong. After 5-10 minutes I started it back up and ran fun the remainder of the day. Bad sensor? Any other ideas?

Thanks,
SHEP

Bravoitis. Your water pickup is clogged and not supplying enough pressure. Just went through it.