496HO issues, help and feedback needed!
 

Hi,

I have a 353 Fastech with dual 496HO from 2001.

Today I "got the 2-beep-a-minute alarm on my smartcraft. No codes thou. Engines runs great, but when turning around 4500rpm port engine goes into guardian with 90% available power and gives me the "crank position sensor fault"? OR just "overspeed"?!

If I lower the RPMs to 4000 everything is fine again?

This dosent feel like the CPS sensor to me. That one usually gives a bad idle and start trouble.

Any ideas where to start? Vacation is coming and I dont want to boat around at 3500rpm then... :)

CPS can give some errors without actually being bad. Overspeed would not put you into Guardian although you do need to make sure not to over-rev the engine when breaking the boat loose from the water; that leads to really expensive (drive) problems.

Are you certain you have no codes?
I'd buy and IAC and CPS and have them with me for the vacation, if it were me.

Also, do you have water pressure gauges? Plenty of water pressure at speed?
Engine temperature fine? Have you changed the antifreeze ever? If not, I would do so. It's only good for a max of 6-7 seasons. When it starts to get grey vs. pink, it's starting to silt up and not cooling your engine as well.

troubleshooting another boat, normally cps just fails. found plurb in manual that failing cps may give false overspeed fault along with hard start on cranking.

Engines do not over rev, I never push the boat hard out of the water.

There is no code of the double beep, It only throws a code when passing 4500rpms on port engine. Then its either overspeed or CPS sensor..

But would CPS sensor give a double beep? Or am I looking at 2 separate faults?

I have water pressure gauges, and the port engine has good pressure, The stbr engine does not have the same water pressure thou.
But I had a dust with the water pressure before and when the pressure gets bad the engine just goes into guardian mode 100%. It doesnt throw the double beep..

Temp is fine and stable, the manifolds nice and cool when running the engines. Antifreeze is pink as...

Ok, Ill try to swap sensors between engines to see if I can move the fault.

Given what you just described, you could have a couple issues; but I am not sure why you are not getting persistent codes in the computer.

Perhaps run the boat with the scanner hooked up (assuming you are using a Rinda scanner), and make sure the electronic sea water pressure of SmartCraft and your gauge are jiving. You might have a cooling obstruction restricting flow at high RPMs enough to upset SmartCraft.

Hi,

I read your post regarding overspeed and guardian mode. And I also remebered an old dust with guardian mode, and that it can throw some codes during guardian which has nothing to do with the actual fault.

Also the symptoms of a bad CPS is not what I experienced, engine is starting fine and runs. Perhaps a bad/low idle.

And the CPS sensors is a PITA to access so I started swapping the sensors that that were easy to access instead.
Once I came to the IAC the fault moved to stb engines instead.

Now port engine runs great and the stb engine has a bad idle and gives the 2 beep-a-minute instead.

Ill buy a new IAC tomorrow.

Thanks for the help! Hopefully this thread can help someone later!

Sounds like an IAC to me They are notorious....