One motor not making full RPM

[matt.schaefer86]

Twin 6BTA 330.
Here is the situation
We were coming in from fishing yesterday and running down swell so I went to push the boat to a higher cruise. That is when I discovered that the starboard motor would only achieve approx 2250rpm. It would hit 2250 on the normal spot on the throttle lever the. You could just keep advancing it and nothing would change. The port motor would rev higher. I went into the engine room while running and I could push the throttle all the way to the stop by hand or with the throttle lever and 2250 approx is what we could get.
So running it like this for a while as we were climbing the back of the swells and then surfing down the motor in question would range rpm a lot. It would go up to 2330 while surfing and down to 2150 while climbing. The port motor would not range very much at all maybe 2270 and 2230.

As a side note there is no other changes. Neither motor smokes durning any of this. Temps good and everything else seems normal.

I am hoping one of the experts on this forum can give me an Idea of where to start?

Topic

[matt.schaefer86]

(Your may need to install a boost gauge and a fuel PRESSURE gauge on the suspect engine to sort this out, or bypass the aneroid with a 20 PSI air pressure source to keep troubleshooting)

Tony
Can you describe this procedure of bypassing the Android?

[matt.schaefer86]

Tony
To clearly answer all questions

The throttle hits the stop 100%
Additionally the motor will hit 3200rpm in neutral

No Sync crap at all. 100% Mechanical

Literally no Smoke at all through the entire power band.

After coolers: these engines are ReMans and have approx 215 hours on them since started in the boat January 2020. They were supposed to have been rebuilt at the time as well.

I will have to get down there and get you a bunch of pictures.

[Tony Athens]

Another avenue to look at-

I want to see your exhaust systems that attach to the turbo–Good clear pics

Last time the aftercoolers were of the engine on on the bench for proper servicing?

Actually, let me “see” the engine (s) from all angles & perspectives that we are trying to sort out..

[Tony Athens]

It would sure be nice when I read thru the issues and ask a very clear question I get the answer to the question I asked. Yes, I do get frustrated when I ask something and that answer is not what I asked someone to answer,.

Either way, you are 100% sure the throttle lever is hitting the WOT stop on the suspect engine?

No sync crap, right?

No dark smoke at all from that engine?

Your may need to install a boost gauge and a fuel PRESSURE gauge on the suspect engine to sort this out, or bypass the aneroid with a 20 PSI air pressure source to keep troubleshooting

[matt.schaefer86]

Tony
I went and ran the boat today. Fully loaded like the other day.
Prior to running I checked the drag guages on the SMX double doubles. It was at 5 well in the green.
I replaced the last chance fuel Filter
Checked the hoses and clamps on the charge tube. Had the exact same results. In the bay could get the motor in question to approx 2320rpm. The other side will continue to build RPM. Runs great and no smoke but the throttle lever reaches 2300rpm where you would expect it to but when you push it further it doesn’t try to make any more RPM.
Today in the bay and fully loaded at 2300 ish RPM the boat would make 21.5 knots

[Tony Athens]

What vessel speed does 2200 RPM yield now?

[matt.schaefer86]

Yes Rob of course 1850 was a typo. 2850 in March.
I typically don’t run around at full throttle.
When the conditions allow and I wanna run fast it is usually about 2400rpm. That gets us about 22-23 knots which is plenty fast on the pacific. Our usual cruise is 2150-2250 getting us 19-20 knots.

[Rob Schepis]

matt.schaefer86 wrote:

Thanks for the reply tony

It made 1850 in March loaded very similarly to yesterday.

You meant 2,850, not 1,850, right?
Both engines?
So you have not pushed the engines to WOT in 5 months?
What is your normal fast cruise rpm, such as on a flat day hurrying out or back from the fishing grounds?

[matt.schaefer86]

Thanks for the reply tony
It made 1850 in March loaded very similarly to yesterday.

[Tony Athens]

When was the last time the engines could reach 2800-2900+ RPM loaded as you use the boat??

[Author]

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