1999 challenger 1800 40-4500 top rpm only in water

[builtnotbought]

Hi ! one of my engine is acting up in my boat. On the trailer it hits 7000 rpm no problem but when I put it in the water it stops at 40-4500 rpm like if there was a rev limiter. There is no smoke or water leaking anywhere.

 

[Dr Honda]

Is it trying to die... or just not reving up?


Regardless... get some compression numbers, and let us know what they are.

 

[builtnotbought]

No it is not trying to die, it climbs quickly to 40-4500 rpm and stops there. I will get compression numbers as soon I get back from work !

 

[builtnotbought]

ok so compression is at 150 psi in every cylinder !

 

[Dr Honda]

Nice. Perfect.


Open the gray box... and disconnect the red wire from the voltage regulator. When they go bad... the can pass AC or the voltage can go high. When that happens... the MPEM and CDI will do crazy things.

 

[builtnotbought]

Sorry but what is the voltage ? here is a picture a my box ! And I disconnect it then try it while it is disconnected to see if it runs good ?

 

[Bill B]

What year is the boat? The 99 has a big black MPEM. 97 has gray box.

 

[Dr Honda]

Sorry. I was at my shop, and typing between CNC parts.

I meant "Voltage Regulators." It's the 2 square boxes, with the potting in them. Top right in your picture. The red wire is the output. Just unplug the red wires, and try to give it a run.

 

[builtnotbought]

Hey sorry it is a 1997 ! Thanks for the help ! I don't know what it did but anyway I unplugged the red wire, gave it a try and it was going good, plugged it back in and was still going good !!! Now driving it on the trailer a weird noise started goin on and found out it broked a rave valve in the other engine. There is a chunk missing on the valve but the piston looks good and compression is 150 psi. what do you think of installing a new valve and enjoy it for the summer hehe !