acceleration issue HELP!

I have a 2001 mc xstar 330 hp about 700 hrs on it. Last season I had a few instances where I could not accelerate past about 8 mph. A few of these times we had been wake surfing for an hour or so at that speed. The cruise was set at 8 but when we wanted increase speed for riding I couldn't go any faster than 8mph (The cruise was reset for 22). The next time out immediately after this happened there was no problem. This probably happened 4 or 5 times during the season (out of about 30 times).

I am not sure if this is a cruise control issue or something else with the engine. Any ideas on what it might be?

Thanks

If you shut off the cruise control and still could not go over 8, then it is probably not a cruise control issue (unless your servo was wound all the way up). Did you by chance turn the cruise off when you were not in neutral, thus causing the servo not to unwind to its neutral setting?

Most likely, your boat went into limp mode, which I have heard can happen due to the excess strain caused by surfing. Were you using more weight than usual?

Yes I had about 800 in the back, 300 center 500 bow. Does surfing put that much strain on the engine? Should I avoid surfing with that many hours on the boat? Are there certain parts of the engine that I should get looked at or replace to solve this? The marina does an overall survey but I am not sure if it is too thorough.

That amount of ballast should be fine. It sounds like you have the 5.7L LTR which is the same engine that I have but I don't have the cruise option, I have Perfect Pass. It sounds like you're referring to the factory MasterCraft cruise system. Is that correct? I'm not too familiar with how that works but I'd suspect that's where the problem lies.

Maybe someone more familiar with the MasterCraft cruise could give you some troubleshooting tips there.

Originally Posted by Jeff

That amount of ballast should be fine. It sounds like you have the 5.7L LTR which is the same engine that I have but I don't have the cruise option, I have Perfect Pass. It sounds like you're referring to the factory MasterCraft cruise system. Is that correct? I'm not too familiar with how that works but I'd suspect that's where the problem lies.

Maybe someone more familiar with the MasterCraft cruise could give you some troubleshooting tips there.

I have the Perfect Pass. It looks like that was from the factory.

There was a really simple cruise system that MasterCraft offered back at that time that I assumed you were referring to.

I'm more familiar with Perfect Pass since I just installed it on my 2000 MariStar with the same engine. I would troubleshoot mechanical issues with Perfect Pass first but it could be a software or an electronic issue which would require assistance and possible replacement parts from Perfect Pass.

There's a servo assembly that's likely hose clamped to a cooling hose on the top of the engine. There's a cable (Similar to a bicycle brake cable) that goes from the servo to the throttle body. On the end of the cable there's an L bracket that the cable housing is attached to. The cable itself passes through the L bracket and attaches to the end of your throttle cable (The big one that comes from the throttle lever).

First thing I would do is open the throttle completely. Then go to the servo and turn the knob manually. Without a whole lot of effort you should be able to open and close the throttle body using the knob. If you feel resistance you may have a binding issue, need lubrication, or the housing/cable could be worn to the point that it doesn't operate smoothly.

If that checks out then I would disconnect the servo connector at the end of that wire and make sure there's no corrosion and maybe put some dielectric grease in the connectors to keep moisture out. if that checks out you could check all of the connections to the Perfect Pass module under the dash.

That's about it for basic troubleshooting. If all of that checks out you will just have to wait for the problem to return. When the problem returns I would try turning the system off, as stated by other posters and see if you can accelerate past the 8 MPH mark. If not that still doesn't eliminate the Perfect Pass as the source of the problem. The servo could be seizing up at higher temps making it not retract the cable appropriately but only allowing the throttle body to partially open even at wide open throttle. Pop the engine cover and look at the servo. I'd bet you see a bunch of slack in the little piece of Dacron cord when the throttle is closed. At that point I'd try turning the knob and see what happens.

The more I talked about the servo seizing at higher temps the more that started to make sense. Surfing with a bunch of weight would tend to make the engine compartment hot due to minimal ventilation compared to higher speed. If that servo seizes temporarily I'd bet it causes exactly the behavior you're seeing.

If you discover that it is the servo you can get a replacement from Perfect pass for around $200 IIRC.

I'll give it a shot. Thanks Jeff