Throttles are pretty uneven, where to start?

[Shipfaced1]

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So I just have a quick question about where to start on the path to even this out a bit? I don't think it is a motor issue. My first thought is props, second is throttle cable? I am not new to running down mechanical issues but I really am kind of behind when it comes to marine maintenance. I know the throttle won't always be even but the pictures show how far off I am when I get the engines synced. I can also feel a difference when we are at idle speeds, it tends to push one way harder and I have to try and even it out by going in and out of gear as well as with the rudders, which I don't like to mess around with at idle speeds.

Any ideas based off a pretty useless picture?

[bud37]

There is no quick answer to this as it could be many things from bad cables,thru distributor advance weights/timing to props......anyway I would start with the simple.....pull throttles back to idle....disconnect the cables from the engine carbs.....start up engines and set the idles to your spec maybe 700 in gear, then adjust and connect your cables back so they neither pull or push the throttle arm.......this way at least at idle your engines will be turning at the same rpm and see what happens from there.
Have a look in the distributors though and see if there is any corrosion/rust inside....its a start, there will be more on the way........
Worn slides for the advance mechanism will produce much the same type of complaint, I have had that and we rebuilt one dizzy and all was well....trouble was getting the right timing curve.......well one thing at a time.

[Shipfaced1]

Thanks Bud,

I assumed there would be a ton of things to cause this, the boat runs great other than the throttle issue so I was really hoping someone would come along and say "oh I know what that is for sure and it's easy to fix" but deep down I 100% knew that wouldn't happen haha. Excited to drop the boat in the water and want to play around with this before the season gets in full swing.

[bud37]

Ha , just realized ......you can cross the props off now, since you are in the parking lot.....just read the size stampings that hopefully are on the props...should be the same.

[Lyndon670]

This was exactly the case on my previous boat, a 97 Silverton 42C. I was able to adjust the cable at the carb which allowed for the stretch.

[Viper]

When you set your cables as mentioned above, make sure the rpm reading you take at the engine matches the reading on the tach. Before you adjust the cable at the carb, isolate the two stations by disconnecting the upper helm cables from the lower helm remote if that's the way your application is set up, then make your cable adjustment at the carb as described above. Make sure when you're done that the remote is in the bottom stop position (idle). This is where it helps to have two people on board; one at the helm and one at the carb. Tell the person at the carb to yell out as soon as they see the throttle arm move. Start moving your remote lever and note how much travel you get before you hear the person yell out. This will give you an indication of how much play your cable has providing you can see on the back of the remote that the cable moves as soon as you move the lever in case the play is in the remote. If you get more than just a slight amount of travel, the cable is stretched or the remote is worn or needs tightening up. If it's the cable it'll be difficult if not impossible to maintain an adjustment that will remain consistent. Once you're satisfied with the adjustment, repeat the adjustment steps for the set of cables from the upper to the lower station or to the carb depending on your setup.

As mentioned, there are a few things that can cause this. One is the props so check that both are the same before you get launched. After checking the props and cable adjustments, you'll at least know you can eliminate those two items.

As Bud mentioned, your distributor can be an issue but I don't know which engines/model you have so I can't comment on that as advance weights may not apply.

When both throttles are at idle, are both tachs reading the same? Have you taken steps to confirm the tach readings actually reflect true engine rpm?

[km1125]

How is your fuel burn on the engines during cruise?? Do you use the same amount of fuel?

IF NOT, then check the choke assembly and secondary linkage. I had an issue a couple years ago where my choke thermostat had broken loose a bit from the housing. The choke would work OK when cold, like it should, but would not stay fully open when warm. This caused the stbd engine to use much more fuel but also caused me to have to push the throttle higher to compensate for slight loss of power. I only noticed the fuel issue after a couple long cruises, but it made sense once I found the choke issue.

I had a similar but different issue a few years prior where the top butterfly for the secondaries would get caught (and I forgot now if it was open or closed) which again caused a misalignment in the throttles to achieve sync.