Alarm keeps sounding!

[Raypex]

Hi all,
I was out boating today. All was well and then I looked at the clock. I needed to pick up the pace. I started to push towards WOT. After about 10 seconds, the alarm sounded. I backed down to idle and It quit. The alarm sounds for three things that I am aware of: 1... Oil pressure, 2... Temperature, 3.... Low outdrive oil.
My gauges were all in spec and I even shut it down to check and add a little engine oil. I continued to investigate by moving through the rpm range and the alarm kept sounding after a few seconds in the 4500 range and would not quit until I slowed to almost idle. It even seemed to start to sound closer to the 4000 range on my last attempts but by then I was at the launch and had no more time to mess with it.
So, does anyone have any theories? I don't know where to start!!!
This is a 2002 Chaparral 265 SSI with a 496MAG Bravo 3.
Thanks for any help!

 

[Raypex]

I think I should add that it has the Corsa captains call exhaust which I opened while on plane. Not at high rpms but I was going at a good clip when I opened the exhaust. Could this be a factor? I was told not to close it at high r's but I thought it was okay to open it.
Is there a temp alarm that monitors exhaust temp?

 

[Fun Times]

Hi there, your 496 engine model has many more sensors that will sound the alarm than the typical 3 often mentioned for carbureted engines. Unfortunately finding them is difficult without having a scan tool connected to the engine sometimes needed during the event if the fault history doesn't pick up on the issue at speed.

Flipping the exhaust at speed shouldn't be an issue and shouldn't of sounded an alarm.

Yes there is a temperature sending unit on each exhaust manifold.

Basically what is probably happening is the engines available power percentage (normally at 100%) is being lowered by a sensor to lets say 90% which in turn would only allow the engine to top out at a programmed RPM of say 4300 RPM. Now with you trying to go over the newly allowed set RPM limiter programmed within the PCM, you're getting an over speed alarm as you advance the throttle over 4300 RPM. Available power can go as low as 5% for critical faults which would force the engine to idle speed. If you tried to accelerate past it, the alarm would sound immediately.

 

[Raypex]

Sounds like I need the boat shop to scan it. I assume this is a merc scan tool, not an automotive one. Am I correct?
Thanks for the reply!

 

[Raypex]

No Title

I have inquired to a few shops, over the phone diagnosis was to replace the impeller. I did and had an overheating issue. The boat was put into the water and revved until water came out the thru-hulls. I thought I was good for a drive but overheated before leaving the marina. Another call to the shop lead me to purge the manifolds via the winterizing pump. When I pressurized the system, only one of the green nipples popped out and it seemed as if only the port side drained. This purge seemed successful and I was able to perform some speed runs without anymore alarms.

But now I am trying to figure out why the water drains arent working properly. I found that the starboard water drain actuator has a 1/4" line coming off the top and goes nowhere. I have looked at diagrams and identified this is a 42" hose #9 on the parts diagram but I have no idea what it goes to!
Does anyone know?

 

[Raypex]

I have been informed that this hose is a vent. I still don't know why only one of the green nipples pops!

 

[alldodge]

Not always but in many cases the issue is the sea pump water pressure sensor. The sensor is located on the power steering cooler and if it doesn't have a good ground it can cause issues. From the looks of your pump this may be the issue.

As for the green nipples, again I'm thinking corrosion. Looks like your in salt water.

 

[Raypex]

Thanks for the reply, AllDodge.
I am a freshwater boater (Lake Michigan and local rivers). I bought this in May from Tennessee where it has been since '08. It was in Virginia from new until '08.
I am going to have it professionally winterized as insurance that all water is evacuated.
I have had no more alarms so I think I'm okay