Volvo Penta Gearbox No Reverse!

[Dave100456]

Hi
I‘d appreciate suggestions as to an issue with my gearbox.
Model Volvo Penta MS25, under 2 yrs old, 220 engine hrs
There have been no problems to date. However when going in to a marina last week, I moved slowly fwd to the dock and then applied reverse......the boat went ahead!
I checked the morse lever and it was in reverse so went to neutral and tried again in reverse which did slow ne in sufficient time to not hit anything.

Before leaving the dock I tried fwd and reverse and all seemed well. I’ve just sailed 400miles including 4 hrs of motoring and have come to anchor and guess what....no reverse gear. When I move the morse lever back I get fwd gear.

I have looked at the Back of morse lever and all parts appears to be moving as they should. The cable is free and moving as it should. The gear lever on the side of the gear box moves from neutral fwd and back into the correct positions so all I can think is it’s an internal issue with the gearbox.

Lastly I should add there is and always has been the correct level and grade of oil (15W40) in the gearbox.

Has anyone got any suggestions of what I might have missed?

Thanks!

 

[Bobc]

Take the connections off at the gearbox and try engaging gears directly at the gearbox lever. If that all works fine, then you either have a problem with the cable or the morse lever.

I had a similar problem with mine (stayed in reverse after put into neutral) a while ago, and it was the cable which was getting stiff, so new cable and problem went away.

 

[richardbrennan]

I am no expert on this and would think a cabling issue is the most likely cause. However, as I understand it, a marine gearbox is nothing like that in a car. Certainly on my previous Volvo engine, a 2030, the forward and reverse was obtained by cones on a shaft. Move the shaft one way and the forward male cone engages with the forward female cone and you get forward drive. Move the shaft the other way and the reverse male cone engages with the reverse female cone and you get reverse drive. If the reverse cone is slipping it might just produce the symptoms you describe, but this would be surprising on a relatively low hours engine. The problem is apparently often a symptom of going rapidly from forward into reverse gear.

 

[Dave100456]

Thanks for the checks.
I have ruled out the cables.
Interestingly, after a 2 hr wait I tried reverse and this time it engaged.
i am beginning to think it’s something in the gearbox that expands with heat and then prevents the selector fork from engaging the reverse shaft. These gearboxes have a raw water feed oil cooler, perhaps an issue with that.

 

[peter gibbs]

Take the connections off at the gearbox and try engaging gears directly at the gearbox lever. If that all works fine, then you either have a problem with the cable or the morse lever.

I had a similar problem with mine (stayed in reverse after put into neutral) a while ago, and it was the cable which was getting stiff, so new cable and problem went away.

Agree, 90% chance this is down to controls not failure of gear box mechanism. Have someone operate gears whilst at pontoon with engine idling and watch operation at gear box. Any asymmetry in movement F/R is an immediate suspect. Only small misalignment / slackness in morse controls will produce the performance you report.

PWG

 

[Dave100456]

Peter and others,
How small does the misalignment You suggest have to be? I had the engine ticking over, and watched the engagement lever move fwd and backward as the morse lever engaged fwd or reverse gears. The engagement lever moved the same angular distance and once the in place you could feel the engagement tolerance in the lever shaft. I’ve compared the angular movement needed for fwd and reverse with the cable attached and with it disconnected and they match. I don’t want to doubt you but I’m 90% sure that it is not the cable.

Looking back at the log and remembering when the problem appeared, it was:
1) soon after the first gearbox oil change.
2) only happens after fwd gear has been used for an hour plus. ( whilst I use reverse frequently without problem). I spend most time at anchor and the only reversing i do is backing down on the anchor, which happens after the engine has been in fwd gear for less than10 mins. On all 3 times the problem has occurred it is after I have had to motor some distance fwd and then wanted to reverse.
3) On the three occasions this inability to get reverse has happened it has mysteriously cured itself after the engine has been off for some an hour is so.

So the question is..... whilst I used the specified grade of oil do the panel think it could be this that is causing the problem?

The VP schematic here. Volvo Penta Exploded view / schematic Reverse Gear MS25L, Components: RATIO 2.27:1 MS25L-A - MarinePartsEurope.com
and here Volvo Penta Exploded view / schematic Reverse Gear MS25L: RATIO 2.74:1 MS25L-A - MarinePartsEurope.com

 

[VicS]

I am no expert on this and would think a cabling issue is the most likely cause. However, as I understand it, a marine gearbox is nothing like that in a car. Certainly on my previous Volvo engine, a 2030, the forward and reverse was obtained by cones on a shaft. Move the shaft one way and the forward male cone engages with the forward female cone and you get forward drive. Move the shaft the other way and the reverse male cone engages with the reverse female cone and you get reverse drive. If the reverse cone is slipping it might just produce the symptoms you describe, but this would be surprising on a relatively low hours engine. The problem is apparently often a symptom of going rapidly from forward into reverse gear.

The MS25 has multiple disc clutches , not cone clutches

Your MD2030 would have had a MS2 gearbox