496ho Losing Speed
 

Hello,

My 496 ho was built in August of 2004 and now has 400 hours. The problem
I am having is I am topping out at 61 mph at 4700 rpm instead of 69 at 5100.
My dealer checked for codes ( I don't remember what is was) when it was on the dunk
and they replaced the impeller for the water pump. The plugs are new as is the fuel filter
and disk. The wires are original. Any suggestion on what the problem could be? The
boat runs and sounds great other then the top speed issue.

Thanks

Prop? And the famous if a 496 is running bad with no codes its the crank trigger.

Hello,

Same problem with both props. What is the crank trigger?

It tells the ECM ignition system when to fire the spark plugs. I'm sure there is a more detailed definition but that's what it does. Right rear of engine, Near bell housing. Also did not know you had twins, that changes thing a little.

crank sensor and its located top back side of engine -

the crank sensor and the cam sensor in conjunction supply the PCM with the timing and rpm signal inputs - then the PCM outputs those signals and adjustment accordingly for a very short jist of how that works.

Spark plugs and check coils for spark properly and or scan the engine - also look for available power in the scan. If it shows 100 % available power then its not in any form of guardian and all coils should be firing 100 % as well..

Thank you both for replying. It is a single engine. Is it a problem if I use my boat until I can have my dealer look
at the engine?

^^^^ lack of your rpms from engine compared to the other could be anything including valve train issue(s), ring / cylinder wear or even ignition related and so on. The valve springs are not the greatest in the 496 along with cast pistons just saying.

And of course it could be a sensor related issue so with that said it needs to be looked at sooner than later.

If it is a crank sensor and it goes completely bad, the engine will not start nor the tach will not work either - the engine can just die while running across the lake and not restart. .