2007 Air Nautique Intermittent Throttle

[Gmund]

I have searched with no symptoms like mine.....2007 Air Nautique with 330 Excalibur

I was cruising around a week ago, on plane, and ran over a medium sized wave. As soon as the boat hit the wave, the RPMs dropped back to 1500. No lights/warnings/alarm. Boat was running fine, just held back in RPM. I stopped in idle. Put it in gear and tried to accelerate - only to be limited to 1500 RPM. No matter how much I put the throttle down, 1500 RPM and no more. I checked to make sure the cable was moving freely on the electronic throttle sensor on the engine (which is was). After 10 minutes of trying to start/restart boat and getting the same results, we decided to go back. My son was driving while I was looking around the engine bay. We were cruising at 1500 RPM but he had the throttle open farther. After a few minutes of cruising at 1500 RPM (and with no change in throttle position), the boat accelerated to plane and was fine. Then 10 seconds later, it slowed to 1500 RPM again. It went back and forth accelerating to plane and the slowing to 1500 RPM in 2-5 second intervals (fast-slow-fast-slow, etc...) Yo-yoing the whole time.

The whole time, the engine is running fine. No misfires or anything. If a throttle position sensor went bad, I would think it would go 100% out. Not come in/out. Without any lights, I wouldn't think limp mode. Any ideas? The boat stays at a marina ~60 miles away so my access to diagnose is not great. I am handy with a multimeter, but not sure what to look for on this boat.

[jpwhit]

What was the engine temp. Sounds to me like it was running hot and the ECM was going in and out of overheat protection mode. I don't think that lights up the check engine light.

[jkallen21]

You mentioned hitting the wake… I had a really weird this year with my 2006 SANTE where I would lose all rivals whenever I would hit a wake of various size. At first, the wake had to be very large. But eventually the wake could ld be pretty small. I tracked this down by using a rubber mallet and tapping around the boat and to simulate a wake. It led me to the kickplate under the driver feet. I removed it and found that the main power cables were no longer securely mounted. It’s an easy thing to check and I would start there.

[Gmund]

1.) The engine temperature was normal, as were all other gauges.

2.) jkallen - yes I have a suspicion that hitting the wake jarred something loose. A little strange because I hit wakes all the time. I am a big causation or correlation person, and I find it suspect that it happened at that exact second. Seems like it had to be something jarred loose. I will start checking things the next time I get under the boat.

If I ever get resolution, I'll let everyone know.

[jkallen21]

To be clear, the spot I am talking about is the plate/board that all the breakers are attached to at the driver feet inside the boat.

[biacs]

One thing to keep in mind is that the systems on the boat for these years are prone to gremlins.

Certainly can't make guarantees but ensure that your ignition spark is running and clean.

This was a tuneup kit I put on my boat, Works fine for the PCM 5.7 / 330.

Distributor Cap, Rotor, Spark Plug Wires and AC Delco 41-993 Plugs. Tune up kit for Mercruiser 5.0 5.7 MPI MAG and Volvo Penta 5.0 5.7 GI GXI https://a.co/d/5jgoLRM

Nice thing is it's easy enough to do at home even if you're not terribly mechanical. I think the boats of this age are due for tuneup either way :-) it helped my issues with the boat going into limp mode at times.


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[mcbridek]

You have two fuel pumps, one inside the fuel cell, and one right next to the fuel cell attached to the engine. The one attached to the engine keeps the fuel cell full... There can be 3 places where the flow of fuel can be restricted to the fuel cell. The most likely - remove the connector at the fuel tank, there is a hose that goes into the tank and at the end of the hose is wrapped with a screen. Disconnect the hose, clean out the screen with carb cleaner and replace. The second place, where the fuel line connect to the tank there is a value that prevents back flow, there is a little ball in the value, spray cleaner into the value to clean... The third place is there is a filter near the fuel pump that is attached to the engine. Someone else would have to comment on that one, or research, I don't remember the exact setup..

My theory, the fuel to the cell is flowing, but not 100%... So the engine is running, draws down the cell and the cell is not being refilled at a flow high enough to keep up with the draw to the engine...

Let us know what you find.. On mind, I replaced both fuel pumps before discovering the problem was the screen in the tank.

[mcbridek]

here are a few pictures should you explore the fuel line restriction. The bottom pic is the line that goes down into the tank,

[Gmund]

Here is a little closure to my original post 10 months ago....

I winterized the boat last fall and didn't deal with it. But when I summarized it this spring, it ran perfectly. So I just used it until.......June 22....... and it went back to 'restricted RPM'.

I was on a compressed schedule and needed my boat fixed quick, so I took it to the Nautique dealer. They had some curious diagnositc challenges, too. Here is a list of what was done, in order, and the findings/outcome. As of today, it is working again. So this might help someone else (even though I am still a little questionable about this).

1.) Dealer said it had a misfire at idle. Even before they diagnosed the throttle, they said it needed new distributor (Part# RA107044). They thought it might cure throttle problem too, but it did not.

2.) They replaced the TCP sensor plate assembly (RA109053A) and the cable attachment ball-joint (R178003). They said that the bracket around the sensor was broken so that when you pushed the throttle, the whole assembly rotated with the sensor. They believe this was why it would not accelerate (seems plausible to me, but I didn't see it myself). However, they lake-tested the boat and it would now go either low speed, or full throttle, but it would stutter and wander in throttle around 3k RPM. Strange.

3.) Next, they read some more codes that indicated a cylinder knock. So they replaced the spark plug wires, spark plugs, and a new knock sensor. Still, the same problem listed in #2.

4.) Finally, they disconnected the Perfect Pass in the ECM. This completely corrected the problem and now works 100% fine.

There is a caveat and questions left in my mind. The caveat for #4. My Perfect Pass gauge has been broken for a few years. In the winter of 2022, I replaced my gauge cluster and just removed the PP gauge completely. The boat had gone into this restricted RPM stage prior to, and after, the removal of the gauge. I am uncertain why it would be an intermittant problem for a ECM programming thing. It would either be 100% broken, or 100% working. Seems odd that turning it off in the ECM just cured it.

But I don't know. My old Honda Odyssey would stop shifting gears if the battery voltage was low. So maybe there are some strange voltage/response correlations. Or maybe, I had multiple issues and the replacement of everything above solved many things at once. My only heartache with boats is there is way less information to help us learn and understand how they work, so diagnosis and solving is harder than cars. Thanks to forums like this for all the help.

For now, I will do what I normally do with electronic boat components - cross my fingers and hope the problems stay away.

[biacs]

Issue I had found with my PP, remove the floor and noticed the paddle wiring was pulled underneath the tank. When I would chatter over waves, the tank would bang enough to smash the wires, causing electrical weirdness.

Pull the paddle wires out from underneath the tank and zip tied them higher. Also upgraded to the GPS stargazer for perfect pass. Didn't have any weird RPM limp mode issues after hitting small waves with that fix.

Also hope you're using known good batteries, that aren't fluctuating voltage. It really freaks out these mid 2000 boats.


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