Limp mode question

[mlcrew94]

So I have been seeing people talk about limp mode and I have a question. I have a 97 challenger 1800 and the engines won’t go over about 4K. The last time out I notice a pretty nice leak in the exhaust where the pipe head meets the pipe cone. Could that lose of pressure in the exhaust cause the boat to go into limp mode? What exactly is limp mode? I just bought this boat and from what I was told it was running fine then the pistons burnt up in one of the engines so he shut the boat down and that’s how I bought it. I rebuilt the top end so in theory I should just be able to put the boat back in the water and go. I just don’t see how it could be carb problems all of a sudden on both engines. Was told the carbs were rebuilt recently and yes I know people will say anything to sell their crap. Lol Any thought or pointers as to where to look for any problems would be great.

 

[jhjesse]

Your boat does not have limp mode capability. I would start with the exhaust leak and go from there.
Low oxygen levels in the engine compartment due to the exhaust leak will effect performance.

 

[mlcrew94]

jhjesse thanks for clearing up that I don’t have limp mode.

 

[2x2smoke]

Lets start with the good news. These boats are fun when they are working properly.

The bad news is that they get abused and take commitment and skill to get working properly. If you buy something without driving it on the water, expect the worst and hope for the best. You are ahead of the game if you successfully rebuilt the top end.

There is no limp mode but there is a switch in the forward/reverse lever that tells the boat not to rev above 3500 RPM in neutral. If your switch is bad, neither motor will rev up even if its in forward or reverse.

Pistons don't just melt down in a good running motor so your theory is flawed to begin with so you have to start at the very beginning of the process. When was the boat last running well, last year?

 

[mlcrew94]

2x2smoke I just meant that before the melt down he said the boat was running fine. Like I said people lie so who knows if it really was. I bought the boat about 3 weeks ago so I have never seen the boat running well. The previous owner told me he has had the boat out about 4 or 5 times this year and until the end when the pistons melted it ran good. Before the season he said he had one engine rebuilt all 4 carbs rebuilt rave valves rebuilt and new wear rings put in but like I said I bought the boat knowing I had to rebuild the top end in the second engine so I never saw it on the water running. How can i test if that switch is bad in the forward/reverse lever?

 

[2x2smoke]

Ok if it was running this year then that eliminates(possibly) bad gas, gummed up fuel system. If you can find the wires going to the switch, you test it with an ohmmeter but I don't remember if its is open or closed in neutral so if its bad, you either unplug it or jumper it to make it work until you replace it. Service manual will of great help.

You can start with minimally invasive tests like compression test. The fuel flows one way throught the fuel pump and carbs then back to the tank. You can unhook all the lines and suck and blow to make sure that gas is only flowing one way. you can take the caps off the rave valves and see if they slide freely.