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Old 29-01-2014, 23:38   #1
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Twins out of sync a little ...

Seems the throttles are a little off with RPM on the Port engine about 300 higher than starboard (according to the tachs). Does it matter if one engine is turning over faster than the other while cruising? (I can move the one to match the other but then the throttle levers are not parallel.)

Annoying but probable an easy fix. Also see the Port is idling higher as well.
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Old 30-01-2014, 02:03   #2
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Re: Twins out of sync a little ...

Cavitation would be my first guess as far as why it matters. The 2nd would be the 'drumming' or vibration felt in the cockpit or elsewhere. It gets annoying but more than that, at certain RPMs, it can be a problem. F'rinstnace, at high RPM. Getting props synched is the key. I wouldn't say 300 is "a little off". Split throttles at the helm is mildly annoying but could be a prob when close in for maneuvering. At that point is becomes one of the peccadillos of this damn boat.


Of course you've contacted engine mfg, right? What do they say? Have cat mfgs even gotten to the point of synching RPMs through syncrophaser?

EDIT: absent any other taletell symptoms could it be your tach gauges are off? What does fuel consumption show? You do pay attention, right?
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Old 30-01-2014, 05:31   #3
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Re: Twins out of sync a little ...

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Originally Posted by eliems View Post
Seems the throttles are a little off with RPM on the Port engine about 300 higher than starboard (according to the tachs). Does it matter if one engine is turning over faster than the other while cruising? (I can move the one to match the other but then the throttle levers are not parallel.)

Annoying but probable an easy fix. Also see the Port is idling higher as well.

Could be a few different causes -- fuel supply, throttle cable stretching, etc. -- but first maybe good to clarify what you mean by "according to the tachs."

Are these IR tachs using flywheel markers to gauge RPMs? Or installed tachs? If the latter, analog or digital? Brand? Purpose of these questions is to determine whether it's your engines... or your tachs...

-Chris
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Old 30-01-2014, 05:40   #4
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Re: Twins out of sync a little ...

Simple way to tell whether it is the engines or the tacho is just listen for a "beat frequency" when the tachos say they are in sync and then moved slowly out of sync.

I'd look at idle stop and throttle cable adjustments for a start.
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Old 17-09-2014, 05:01   #5
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Re: Twins out of sync a little ...

Is the port one using lots more fuel as well?


Djbrisvegas from Brisbane, Queensland
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Old 17-09-2014, 05:20   #6
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Re: Twins out of sync a little ...

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Simple way to tell whether it is the engines or the tacho is just listen for a "beat frequency" when the tachos say they are in sync and then moved slowly out of sync.

I'd look at idle stop and throttle cable adjustments for a start.
This, but coming from a power boat back ground you just get used to the slight mis-match of the levers..
A couple of boats ago one engine would turn a couple of hundred RPM higher with both at full throttle. After chasing everything trying to get a couple of hundred RPM more out of the low engine, I finally came to the conclusion one prop was slightly pitched different. I guess the point being, even though they are exactly the same, they will be a little bit different.
You will get to where you sync by ear not the tachs
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Old 17-09-2014, 05:20   #7
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Re: Twins out of sync a little ...

I would buy/borrow/rent a hand held electronic tach and see what the engines are doing in identical throttle positions. Most good throttle controllers can be tweeked right at the control station to compensate for wear/stretch. You should easily get them within 25-50 rpm of each other.

No biggie
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Old 17-09-2014, 19:00   #8
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Re: Twins out of sync a little ...

How far off are the throttles? I've had multiple multiengine boats and the throttle levers are never "exactly" in the same place when the engines are synced. I wouldn't sweat it if they are in the same general area and both will idle and get to WOT.

Try syncing triple engines when the boat is doing 55 mph. Now that's frustrating!

I just got hooked by the dreaded thread resurrection...
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