Throttle cable question...2004 340 DA

[nowakezone]

My port engine revs well above 4600, the starboard engine revs only to 4300. The engines are tuned and there's no prop or shaft damage.

The port throttle lever continues to add revs as long as I want to keep pushing it forward...so 4750 is as high as I've tried it, and only once. The starboard throttle pretty much quits adding revs about 2/3 forward....the last 1/3 does nothing.

In my pea brain the port throttle cable is too tight, and the starboard is stretched. However, I don't even know if that's "how it works."

Thanks for your help guys.

 

[mquiet]

Wow, I have the exact same issue with our 340DA. I had a dock neighbor come over and he said it all looked fine, but I can not get the same revs out of the starboard engine. I also agree with the position of the throttle lever and the rpm response. Any thoughts?

 

[nowakezone]

Trying to read as much as I can find but I can't find anything that pinpoints the issue. One entry which seemed to apply to the starboard issue said that if the throttle is all the way forward and rpm's back off immediately when pulling the throttle back then it's a cable issue. That's not my case. At 2/3 throttle it reaches 4300 and no more for the last 1/3. It doesn't start backing off until I return from full to 2/3. Not being able to reach 4600 only effects high rpm speeds which I don't care about. It's within the WOT range so the engine shouldn't be overloaded.

The port engine, really that's just a matter of aesthetics although I'd like it fixed. And, I don't routinely run at WOT, but do so periodically because you're supposed to. So I can stop advancing the throttle at 4600 and it's all good.

Either way, I do know that throttle cables can stretch. I don't know if they can be too short or too tight and create the over-revving situation I have.

Btw I should add that both engines idle just fine.

 

[Alegria]

I have different conditions throttles then you but mine have a hi point adjustment screw under the cover. Perhaps yours are similar. Having that adjustment off might cause the condition you are seeing.

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[nowakezone]

Throttle cables questions....

I have a similar thread in another section but I don't think that section gets read as much as this one so I'm asking here....

It's not uncommon for a throttle cable to stretch over time. If a throttle cable is stretched, can it manifest itself by not allowing the rpm's to progress beyond 2/3 of the range of the throttle? In other words, at 2/3 throttle my starboard engine rpm's stop progressing over the last 1/3 of throttle travel. Can this be caused by a stretched cable?

The port engine can rev well past the WOT max of 4600 rpm's. Can this be caused by a throttle cable that is adjusted too tightly?

The engines are tuned properly, and there is no damage to either shaft or prop. The props are the stock Teignbridge 18x21.5 port, and 18x21 starboard.

Thanks for your help.

 

[JVM225]

Re: Throttle cables questions....

Can you have someone check the travel at the engine while you run the boat?

 

[nowakezone]

Re: Throttle cables questions....

That seems to be a question that needs to be answered JV'. Thanks for raising it here. Not can I have someone etc, but that the travel at the engine needs to be checked. Your post reminds me that elsewhere on the interweb that question was raised. I need to think about how I could do that while my wife drives the boat. Non-mechanically inclined as I am, my first step will be finding the cable in the bilge. If it's easily visible I can spin both engines up to where the port is at 4600, then have my wife take the helm while I compare the port with the starboard.

However, are you saying that a stretched cable can be a cause, or a tight cable can be the cause as asked above?

 

[nowakezone]

Re: Throttle cables questions....

It's interesting how changing one word of a search can provide all kinds of new information. In this case, when searching for Mercury Horizon 8.1S throttle cable, I changed "cable" to "linkage." Here is the second entry returned:

Owner

I have twin mercury 8.1S horizons. One engine will do the manufacturer specs of 4700 top rpm. the port engine will only go 4320 rpm. I recently had both props tuned and no issue there. The throttle was checked and does open fully. however when the throttle is push halfway the max is 4320 rpm whats up...The port engine and starboard both show 4320 at half throttle. Push all the way forward the Port stays at 4320 the starboard goes to 4750 rpm,

Sounds pretty familiar right?

Mechanic

Is there a change in the sound of the port motor when you move the throttle to full?

Owner

No engine sounds the same.

Mechanic

What you likely have is a problem with the throttle position sensor (TPS). It sounds like yours is only reading an increase up to a certain point. 4320 to be specific. The throttle position sensor is what the ECM uses to decide how long the injectors stay open. So if your sensor is not reading beyond a certain point, the ECM thinks the throttle is only being opened, in your case, about half way. so only enough fuel is being supplied to give you the 4320 rpms.It is mounted right on the throttle body. The rod that the butterfly that you checked to make sure was opening all the way is mounted to, is what actuates the TPS. It is immediately behind the spark arrester and has wires plugged into it. In order to install it correctly Mercruiser states the throttle body needs to come off. This is to insure that the butterfly is fully closed. Since you have two motors, you can test the TPS by swapping them between engines.

If you are considering taking the boat in to have this done, It would be better just to have the motor hooked up to the diagnostic tool and the voltage drop test done on it. This would keep you from having to replace the gaskets on both of the throttle bodies. It is what the shop would do anyway, and the cost would be the same less the other motors gasket.

So there you have it....I'm going to keep reading...but this looks pretty good.

 

[MonacoMike]

There is no need to double post as most of us use the "New posts 24 hours" and will find your question. I will let Chuck know to consolidate them into one thread. Good luck with your problem, MM

 

[MonacoMike]

Re: Throttle cables questions....

Deleted.

Good luck with your problem, MM

 

[IanBat]

There is no need to double post as most of us use the "New posts 24 hours" and will find your question. I will let Chuck know to consolidate them into one thread. Good luck with your problem, MM

So why did you double post Mike? (Tongue in cheek)


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[chuck1]

Threads merged. Thanks for the heads-up Mike.
And yes please only one thread per topic.

 

[nowakezone]

You have got to be kidding me. You guys playing footsie later on?

By your logic Chuckie then no other thread other than this one should address throttle cable issues. One thread per topic.... better merge all the threads looking for new carpet into one thread then. What a joke.

"Thanks for the heads up, Mike" hahaha.... Mike likes to have his head up things, apparently you like it too. Well you guys go hold hands and do what you do. I'll leave now and not return. Don't want you to have the pleasure of banning me. But, you have my email...if you or your girlfriend Mike ever want to talk about this in person, let me know. Until then...bye bye girls.

 

[carterchapman]

Wtf, o?

 

[techmitch]

You have got to be kidding me. You guys playing footsie later on?

By your logic Chuckie then no other thread other than this one should address throttle cable issues. One thread per topic.... better merge all the threads looking for new carpet into one thread then. What a joke.

"Thanks for the heads up, Mike" hahaha.... Mike likes to have his head up things, apparently you like it too. Well you guys go hold hands and do what you do. I'll leave now and not return. Don't want you to have the pleasure of banning me. But, you have my email...if you or your girlfriend Mike ever want to talk about this in person, let me know. Until then...bye bye girls.

Let us know when you land!

 

[chuck1]

Nowakezone, don't know what your problem is. Very simple you don't have to post the same thing in multi places. Have a good day sir.

You have got to be kidding me. You guys playing footsie later on?

By your logic Chuckie then no other thread other than this one should address throttle cable issues. One thread per topic.... better merge all the threads looking for new carpet into one thread then. What a joke.

"Thanks for the heads up, Mike" hahaha.... Mike likes to have his head up things, apparently you like it too. Well you guys go hold hands and do what you do. I'll leave now and not return. Don't want you to have the pleasure of banning me. But, you have my email...if you or your girlfriend Mike ever want to talk about this in person, let me know. Until then...bye bye girls.