Throttle jumps in gear while in neutral?

[jblakes]

Our Volvo KAD44 port engine jumps i gear while on tick over! This happened while i was on the pontoon and suddenly the boat started moving about while luckily still be well tied up. The mechanic has changed the throttle potentiometer but the problem seems to keep on coming back especially when mooring!!. We also have an intermittent drop in revs from 3250rpm fluctuating 2250rpm while cruising. The mechanic has also replaced many of the connections on the engine too. I would appreciate any thoughts on the matter as this is a very dangerous fault that needs a permanent fix?

 

[scottie]

Try a Private Message to either Volvo Paul or spannerman they are resident experts

 

[jblakes]

Try a Private Message to either Volvo Paul or spannerman they are resident experts

Thank you for that Scottie

 

[BruceK]

Didn't this happen to @petem ? He may have discerned the answer

 

[BruceK]

I recently helped a friend who had a not dissimilar problem when gear changing was a bit erratic with his KAD44. In the end after clearing ALL the faults off the engine (more than 1) and then swapping over to a spare throttle assembly and known good actuator and doing a calibration we were able to discern that one actuator was fubar (microswitches gone) and the throttle potentiometer gone. It took ages because of the double fault to work that one out. I mention this as this would not have been resolved if ALL faults had not been cleared (we were only clearing the first initially) and if we couldn't borrow a spare throttle assembly from a kindly engineer. Before the throttle assembly change and fault clearance swapping over actuators didn't solve the issue and when returning the good actuator that engine also started throwing out faults and not engaging gear.

 

[volvopaul]

Our Volvo KAD44 port engine jumps i gear while on tick over! This happened while i was on the pontoon and suddenly the boat started moving about while luckily still be well tied up. The mechanic has changed the throttle potentiometer but the problem seems to keep on coming back especially when mooring!!. We also have an intermittent drop in revs from 3250rpm fluctuating 2250rpm while cruising. The mechanic has also replaced many of the connections on the engine too. I would appreciate any thoughts on the matter as this is a very dangerous fault that needs a permanent fix?

I’d say your engineer is swapping parts at your expense and has no idea what he is doing .

 

[petem]

I’d say your engineer is swapping parts at your expense and has no idea what he is doing .

What are the likely causes then Paul?

 

[petem]

Didn't this happen to @petem ? He may have discerned the answer

Hi Bruce, our issue was slightly different, the engine was hunting in neutral but didn't actually try and engage gear (thankfully). We're hoping that our issue was due to duff batteries and possible a faulty ECU that we have now replaced.

I've heard of other KAD44 / KAD300 boats that have engaged gear at random. I believe this is due to erratic signals from the throttles and in some cases has been cured by the aftermarket addition of a SPM module. This thread gives more info...

Volvo KAD 300 losing revs

The intermittent drop in revs from 3250rpm fluctuating 2250rpm while cruising sounds like knackered turbos.

Hopefully @volvopaul can add give some professional advice.

 

[jblakes]

Hi Bruce, our issue was slightly different, the engine was hunting in neutral but didn't actually try and engage gear (thankfully). We're hoping that our issue was due to duff batteries and possible a faulty ECU that we have now replaced.

I've heard of other KAD44 / KAD300 boats that have engaged gear at random. I believe this is due to erratic signals from the throttles and in some cases has been cured by the aftermarket addition of a SPM module. This thread gives more info...

Volvo KAD 300 losing revs

The intermittent drop in revs from 3250rpm fluctuating 2250rpm while cruising sounds like knackered turbos.

Hopefully @volvopaul can add give some professional advice.

Definately not turbos' as both were new last year.

 

[petem]

Definately not turbos' as both were new last year.

Unlikely to be Turbos then (Vodia would be able to read the boost) to eliminate this.

Boost sensor at the EDC end perhaps?

 

[jblakes]

Thanks everyone for all your help.. i'll pass on the info and let you know the outcome.

 

[zt260]

I had this problem with kad300 they would jump into gear without warning normally when mooring or close quarter work,a forum member told me to disconnect the large grey electrical connector block found on top of the engine body.disconnect and clean connections.this worked for me

Reyes ash

 

[frenzy]

I had similar problems a few years back On my KAD 300. The boat would lose revs and then jump into gear on it owns. Tried calibrating but no joy. Eventually fitting a unit called SPM which seem to sort the problem . The unit is fitted at the controls and is very easy to fit.