Wandering Throttle / Power surge issue

[mylesm260]

4.3 EFI
Alpha-1 MR
2 year old controls (throttle/gear)


When cruising (1/4 - 3/4 throttle, 2000 - 4200 rpms or so), the engine seams to randomly loose, then gain power.

I haven't had a chance to take anything apart yet, as my tools are in storage (moving). but this is what I know so far.


There is some play in my throttle cable. I can start the engine, push the throttle only button, and bring the revs up to 2000 rpms, and then move the throttle forwards and backwards about 1 1/2 inches without any change in RPMS. Is this normal?

Also, the sift linkage seams to change as the boat heats up. When the boat is cold, shifting into fwd is perfect. You move the lever forwards, the gears engage, then you move it a little further and the revs go up. If the engine's warm and I let it the boat sit for 20 minutes or so, when I go to put it in gear, the revs start to go up before the gears engage.


Also, with the engine off, if I put the throttle at 50% for example, I can move the throttle cable on the throttle body about 1/2 an inch or so ether way (without the actual hand throttle moving)


IS this slack in my throttle cable the cause of my boats random increases or decreases in speed while cruising?

What's the most common cause for this slack, and how do I fix it?


My other thought process was that one of my cylinders is cutting out. either from an ignition issue or a intermintantly failing fuel injector.
I have new plug wires this season, and my plugs, cap and rotor were changed last season.

The random increases or decreases in power "feel" like a the boat is running on 5, then 6 cylinders.....

I'm trying to figure out if I should start looking closely at the throttle cable and linkage, or my injectors/ maybe ignition system.

Seeing as how I know somethings already fishy with my throttle cable, I have a pretty strong feelings it's going to be the cause, but, If you think about it, there is a return spring on the throttle body. It should always have tension pulling on the throttle cable which should in theory stop it from "wandering"

 

[danond]

Re: Wandering Throttle / Power surge issue

Have you watched the engine-side of things while someone moves the throttle control around to see if the issue is obvious?

 

[mylesm260]

Re: Wandering Throttle / Power surge issue

It seams like the choppiness of the water triggers increases or decrease is power.

But yes, looking at the throttle body, and moving the throttle with your hand, you can see there is definitely some play in the systems. Not sure where the play is though... The cable is solid, so I'm guessing the play has to be in my controls.


Here's the control I'm using.
http://dc87.4shared.com/download/63864133/f9ea19bb/Commander_3000_Classic_panel_mount_sec_11.pdf
Commander 3000

 

[Bondo]

Re: Wandering Throttle / Power surge issue

It seams like the choppiness of the water triggers increases or decrease is power.

Ayuh,... Change the Fuel Filters...

 

[danond]

Re: Wandering Throttle / Power surge issue

Controls are pretty easy to disconnect, if you think something is loose, disconnect the cable from the control and move it with your hand. See what you get.

 

[mylesm260]

Re: Wandering Throttle / Power surge issue

I'm EFI'ed, if I had any fuel filter issues, my external high pressure fuel pump would not be happy, and it would be pretty obvious, I think. Also, if I was loosing this much power from running lean, I would be expecting my engine to backfire through the intake.


In terms of the linkage, is this kind of play normal for a throttle cable?

 

[mylesm260]

Re: Wandering Throttle / Power surge issue

Here's some more information....

Boat idle's fine, WOT is fine.

And the "changes" in speed/power happen randomly... It makes wakeboarding quite challenging...

Here's an example... Wakeboarders in the water, you engage into FWD, put tension on the rope, to go WOT, get the wakeboarder up, then pull back to 1/3 throttle or so to get the boat just barely on plane. After crusing just barely on plane for 30 seconds to 2 mins or so, all of a sudden the boat starts accelerating all on it's own, and it will go from 2700 RPMS or so to 3500 (without touching the throttle).. This makes it very difficult for the wakeboarder.


If my fuel filter was the cause, you would think I would have WOT issues or idle issues, but I don't. The motor idles perfectly, and every time you open the throttle all the way, it pulls hard... no backfiring, no stuttering..

 

[Bondo]

Re: Wandering Throttle / Power surge issue

If my fuel filter was the cause, you would think I would have WOT issues or idle issues, but I don't. The motor idles perfectly, and every time you open the throttle all the way, it pulls hard... no backfiring, no stuttering..

Ayuh,.... For a 10 dollar Experiment,... Change it,.. Either I'm Wrong, or You are...
Dump the 1 you take off into a large container,+ Look for Water....

 

[mylesm260]

Re: Wandering Throttle / Power surge issue

You're right, for the 10 bucks, I might as well.....


Have you ever heard of a bad fuel filter causing an issue like this?

Idle / WOT okay, but random changes in power while cruising?

 

[cooter2506]

Re: Wandering Throttle / Power surge issue

Yep been there repalced filter and it ran fine. ALso might want to check your antisiphone valve at he tank.

 

[bruceb58]

Re: Wandering Throttle / Power surge issue

You're right, for the 10 bucks, I might as well.....


Have you ever heard of a bad fuel filter causing an issue like this?

Idle / WOT okay, but random changes in power while cruising?

I change my filters every year...do you? it should be part of your annual maintenance.

Really sounds like your shift interrupter is getting engaged and this may be caused by your lower shift cable failing from all the other things you mentioned.

 

[mylesm260]

Re: Wandering Throttle / Power surge issue

Shift cable was done last year, as well as all the bellows, gibal bearing, u-joints and fuel filter.

And no, the shift interrupt isn't engaging. That cuts power to the ignition entirely, if that was happening, I would be running on zero cylinders =)

I will get in there and figure it out, the fuel filter's a good suggestion, even though my gut instinct tells me that if it was the fuel filter, I would have other symptoms.

First thing I've gota do is take apart the controls and figure out where that slack is coming from in my throttle cable.

 

[Bondo]

Re: Wandering Throttle / Power surge issue

Here's an example... Wakeboarders in the water, you engage into FWD, put tension on the rope, to go WOT, get the wakeboarder up, then pull back to 1/3 throttle or so to get the boat just barely on plane. After crusing just barely on plane for 30 seconds to 2 mins or so, all of a sudden the boat starts accelerating all on it's own, and it will go from 2700 RPMS or so to 3500 (without touching the throttle)..

Ayuh,... With the Nose Up attitude the Water is sloshing around the Tank, or the Filters, or Both....
Atleast that's My Theory,.. And I'm stickin' to it...

 

[mylesm260]

Re: Wandering Throttle / Power surge issue

Makes sense.

It could also be the throttle cable itself bouncing around and something being not right with my controls....

I mean... is that kind of play in the throttle cable normal?


This problems' been going on for awhile (about 5-8 tank fulls now), The only reason I'm really concerned about it now is I've started wakeboarding, and it's hard to wakeboard when the boat has a mind of it's own in terms of speed.