496 problem
 

Hi. My brother has installed a 496 375hp -05 in his wellcraft nova 25xl and bravo. We cant get it to rev more than 2500-2800 rpm. We have tried 2 props one 23 and one 17 I think. With the 17 propp it should not be any problem to rev couse it workt with the previous engine 260 5.7l. We have 100% power acourding to the ecm reader and no strange fault codes, we have normal fuel pressure. What to do?

does it rev up higher on neutral ?

Rev limiter isn't going to let it rev up in neutral. Make sure you are getting 100% power, that you're not in guardian mode. You'll need to hook it up to a diagnostic tool.

push throttle all the way open at helm, remove flame arrestor and check to see if throttle blade is full open.

Are you checking fuel pressure at idle or while under load trying to come up on plane? If the booster pump is missing or not working, your fuel pressure will seem fine at idle but drop significantly when you put a load on the motor.

Fuel pressure only tested without gear in.

diagnostic tool say 100% power and we have fooled the ecm that gear is always in because we have an old bravo.

It revs normal on neutral.

We will test fuelpressure on load. The boat cant go to plane now.

thanks for quick reply

Fuelpressure is ok on load so no problem there. Can it be some problem with the ecm? it was missing so its not the original one now.

The exaust is under water but we tried just put it in free air but same problem,but we noticed it smells like its getting lots of fuel it stinks gasoline.

What year model is the 496 -375HP engine?
What is the model type number and year on the ECM Label and does it say 496 Base, or 496MAG HO on the label.?
Is the engine a Horizons inboard model or digital throttle engine?
I think your problem is probably ECM non-compatibility with the engine year and model.
Did you scan the engine for fault codes and if so what were the codes?

Best Regards,
Ray @ Raylar

Having similar problem on 08 525EFI, but after about 5 seconds it then takes off. Had couple of different mechs. look at it, scans, everythink appears to be ok. Also wondering about PCM, or possible ground issue. Was also suggested to change out cam sensor, but haven't yet. I'll keep you posted if I find problem.

Hi

orginal box has the following number VK00SW21
PCM 0308M 03-18-2004
885557 Cant se if its a Base or HO on the ECM.

We replaced this box with a Mag box from a 2002 496 mag
And also tried a box from a 496 HO 2002

Could there be any problem with ECM not from the same year ?

Erik / Peter