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496 ho engine problem

badmedicine

New member
at 3500 rpms or so once the bo

at 3500 rpms or so once the boat gets on plane an alarm goes off and the boat rpms go down to almost a stall. all gauges are good. put it in neutral and it goes off until you rev it up again in drive. does not do it when it is reved up in neutral only in drive. someone told me it can be an inline fuel filter clog. i changed all of the other filters. anyone have any ideas. i am new to this just bought the boatt and want to get it back in the water before the season is over. please help. thanks
 
"A clogged primary filter or a

"A clogged primary filter or anything else that would cause a fuel restriction of low fuel pressure will not set an alarm, so it's not that. There is an active fault(s) that is triggering the alarm and Engine Gaurdian mode.

It's hard to say what the fault is, it could be a lot of things, but a few of the more common causes are low Seapump Pressure, high EMCT (Exhaust Manifold Coolant Temp), IAC (Idle Air Control) fault, or a Shift Switch fault. None of these faults will cause any change on the gauges. It may not be a big deal, but you really need a scan tool to connect to the engine and see what the fault is."
 
"Was the boat operated in salt

"Was the boat operated in salt water? I had a very similar problem on an '03 496 Mag HO...mine would get up to 4,000 RPM and go into guardian mode...but would not throw off a code...very troublesome. In short, mechanics changed the seawater pump as they detected insufficient water flow/pressure at high rpms...did not solve the problem. They then removed the outdrive and discovered that the fitting which goes through the transom was 75% blocked w/corrosion, etc. They changed out the fitting and hoses in the outdrive and all is now fine. Took almost a year to diagnose and $2,000 but now I'am satisfied."
 
"Tom, that clogged transom fit

"Tom, that clogged transom fitting is VERY common in salt water, I see it at least once a year here in FL."
 
thanks for all the suggestions

thanks for all the suggestions. It is a saltwater boat. Really sucks that i cant even get anyone in the area to make time to scan it for me for codes. They all say 2-3 weeks for an appointment. Its crushing my summer! i will try some of those suggestions myself. thanks again
 
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