454 385hp Efi problem
 

I have a 1990 23ft Nordic I put a 2009 454 385hp Efi motor in it and I ran it full throttle and can only get 4200rpms 57mph out of it and then it falls on it's face I don't know where to start anyone got any ideas what the prob could be inanition plug wires it's got to be something simple cause it's not lackin power on it's way up to 4200rpm its just when I get there it won't go any more and I know it's got alot more I think I should be runnin 4800rpm at around 70mph please help me thanks

Fuel pump?

Check for codes first, I had a similar issue on mine and it ended up being weak fuel, the knock sensor where retarding my timing way back.

Did you try and blow the prop out and would rpms stay the same.

That's a good idea I'll have the codes ran, what do you mean blow the prop out?

Good idea I'll have the codes ran what do you mean blow the prop out?

What prop are you running? Im guessing a 23p would be about right for the engine and your type of boat....
Have you checked compression? Fuel pressure? Timing? How many hours on the motor?

stupid? are you trimming the drive up ?

454 385hp efi problem
 

sounds like water in the fuel, check your water seperator, and check how much pressure your fuel pump is putting out, fuel pump may be going out!

I'm runnin a 23p and yes I have to trim it up to get 4200rpm

fixx
 

then i would start with draining the tank and start with fresh fuel and filter..also do a cylinder ballance test to make sure all the cylinders are fireing..easy way is to remove each pluf wire fron the sparkplug,,make sure your wareing rubber gloves..if it seems like its hitting on all the cylinders check fuel pressure if its like 43 psi then remove all the injectors and send them out to be cleaned and new screens put in them..dont run the boat like this,,you will ruin the engine..