C28 Low Speed - transmission ?

[JonR]

I use the low speed setting in my 2014 C28 to fish. However, I'm a little frustrated with how it acts above roughly 1.5 to 2 knots. At those speeds it feels and sounds as that it's right at a gear transition - it's quite noisy and 'clunky' - it's a little hard to explain. If I push it past that 'noisy/clunky' zone it smooths out again around 3 knots. For clarity, my 2014 C28 has the volvo penta D4 260 engine. Is this a normal behavior or is my transmission in need of repair? I have validated that transmission fluids are correct.

Sincerely,
Jon Rider

 

[Headlee]

I have the same engine in a 2015 C28. I have operated it in the same manner, but have not heard the noise you described. Sorry.

 

[Kevin Lamont]

I use the low speed setting in my 2014 C28 to fish. However, I'm a little frustrated with how it acts above roughly 1.5 to 2 knots. At those speeds it feels and sounds as that it's right at a gear transition - it's quite noisy and 'clunky' - it's a little hard to explain. If I push it past that 'noisy/clunky' zone it smooths out again around 3 knots. For clarity, my 2014 C28 has the volvo penta D4 260 engine. Is this a normal behavior or is my transmission in need of repair? I have validated that transmission fluids are correct.

Sincerely,
Jon Rider

Hello Jon,

When was the last time you had the transmission serviced? There is a transmission filter that needs to be serviced that may have some debris indicating a problem. Also have you checked that hardware for the low speed and shaft coupler? That might be a good start to finding a possible problem.

Thanks,

 

[baz]

Jon: I have the same exact issue on my 2019 R29 CB. The low-speed hardware and software was installed by the La Conner Maritime a little over a year ago.

I agree, the sound is somewhat described as being "Clunky", and in my case it sounds like a metal 'clanking' sound. I would say the weird sound happens around 2 kts and moving the speed up a tad lessens and eliminates the funny sounding noise. At first I was thinking it was my auto pilots pumps stalling as I typical troll with auto pilot heading engaged. However, now seeing your post I think otherwise.

There's a toothed ring attached to the output shaft coupler and there's a stationary magnetic sensor that picks up signals from the ring's tooths as they pass by, and this signal info is used by the engines software to regulate the speed as set by the helm throttle. I'm wondering if there's some adjustment needed for the stationary magnetic pickup sensor as the gap between the sensor's probe is but a few Gnat whiskers from the rings teeth. If there's contact between the sensor's probe and the ring teeth it will obviously make some weird noise.

I'm having my engine service in a few weeks time and this aspect will be examined. With engine in neutral is should be easy to rotate the prop shaft to see if there's any contact as I described, or if the sensor needs securing if it's a bit loose.

I'll keep you posted, and if you can also determine how the noise is created post back here. Thanks.... 🙂

[EDIT]
Let me also add a couple of things that come to mind.

1) This noise only started to happen a few months ago.

2) When the noise is heard I notice my engine idle speed RPM of 700 drops momentarily to 690 and then back to 700. It cycles like this while the noise is heard. Once I adjust the speed on the helm engine throttle lever the noise stops and the engine RPM remains steady at 700.

3) My understanding of how the low speed feature works when engaged is that the special engine low-speed software is receiving the signals from the magnetic pickup and the rate of the signals is what is used by the software to adjust the clutch slippage and hence the RPM of the output prop shaft to attain the requested speed as per the throttle lever's position.

4) I'm speculating here - the magnetic pickup probe is secured to the engine's block in some manner (a bolt is assumed).If the bolt has loosened a tad this may in fact be the cause, and a simple bolt tightening and proper position for the magnetic probe is all that's required to remove the issue.

 

[Robbren]

I have a 2014 C28 and have the same issue...had it in to the dealer 1/2 dozen times for that issue and they could not resolve it so I mounted a 15 hp extended shaft merc with remote steering on centre of swim grid For trolling purposes. I used the merc because it had the longest shaft on the market at that time.

 

[JonR]

Thanks for all of the above responses. I have some answers now. I had an issue that required that I pull the engine. That's a story for another time other than to say 'watch dropping FOD (foreign object debris) into your bilge'. It only takes a small socket to cause major issues. There is very little space between the oil pan and the hull. In any event, since I was pulling the engine I took the tranny in for servicing. The clutches were worn - most probable reason was forgetting to switch out of low speed mode after trolling. Something I have to admit that I have done on several occasions without realizing it immediately.

In layman's speak (as explained to me) - switching into low speed mode reduces the hydraulic pressure against the clutches which allows them to slip against each other slightly - not an issue when trolling and resulting in lower speeds. However, if one forgets to shift out of the low speed mode and cruises in that mode, the reduced pressure causes significant wear on the clutches. As a side note, I also discovered that both my rear motor mounts needed to be replaced. Not sure if the two issues were related?

As is often the case with boats - it was an expensive lesson to learn: DON'T CRUISE IS LOW SPEED MODE. It's too bad that you don't get a warning if you inadvertently do this....