Volvo MS25 A-A (ZF 25 MA) delayed engagement of gear

[impi]

Hi Fellow sailors,

I am posting on behalf of a fellow cruiser who is not English speaking and wonder if we can help him out here.

He has a yacht with a ZF 25 MA (Volvo MS25 A-A) marine box and finds that when he shifts into gear it takes a while before the gears engage. Also, with the engine in idle and with the prop turning he finds he can hold the prop stationary by hand - I am not sure if this is before or after the gears lock in.

He tells me he has tried everything - he has the correct oil at the correct level, the box has 1000 hrs use and he is the 'careful sort'.

The situation seems to be gradually getting worse with time in that the delay between shifting the lever forward to when it actually engages on the plates is becoming longer.

Is anyone out there able to assist?

[DougR]

There are a couple of things to check..

First, make sure that there is .020" or .5 mm clearance between the shift lever and the shift lever cover, so the lever isn't binding.
Then, make sure that the shift lever has equal travel in both the forward and reverse direction. Remove the shift cable from the lever and place/tape a piece of cardboard behind the lever, between the lever and the gear case. Now when in neutral, use a pencil and mark a circle on the cardboard thru the hole in the lever where the cable was attached. Then move the lever all the way to forward position, and make another circle on the cardboard thru the hole in the lever. Now move the lever all the way to reverse and make another circle. Remove the cardboard and measure the distance between the neutral circle and the in gear circles. They should be the same distance. If not, loosen the four bolts holding the shift lever cover to the gear case and tap the cover fore or aft, tighten the bolts, and repeat the measurement.

Make sure the shift cable attachment stud,when in neutral at the shifter, aligns with the hole in the shift lever and goes into the hole without moving the cable or lever.

Normally, unless there is wear on the clutch plates, this will resolve the problem.
DougR

[impi]

Originally Posted by DougR

There are a couple of things to check..

First, make sure that there is .020" or .5 mm clearance between the shift lever and the shift lever cover, so the lever isn't binding.
Then, make sure that the shift lever has equal travel in both the forward and reverse direction. Remove the shift cable from the lever and place/tape a piece of cardboard behind the lever, between the lever and the gear case. Now when in neutral, use a pencil and mark a circle on the cardboard thru the hole in the lever where the cable was attached. Then move the lever all the way to forward position, and make another circle on the cardboard thru the hole in the lever. Now move the lever all the way to reverse and make another circle. Remove the cardboard and measure the distance between the neutral circle and the in gear circles. They should be the same distance. If not, loosen the four bolts holding the shift lever cover to the gear case and tap the cover fore or aft, tighten the bolts, and repeat the measurement.

Make sure the shift cable attachment stud,when in neutral at the shifter, aligns with the hole in the shift lever and goes into the hole without moving the cable or lever.

Normally, unless there is wear on the clutch plates, this will resolve the problem.
DougR

Thank you Doug, I will pass this on. As far as I know none of this was done - will advise.

[Gipsy4]

Thank you very much, Doug. This is Gipsy4 and I am the one, for whom Impi posted the request.


I did what you suggested and found out, that shifting into Forward by hand directly at the lever (control cabel detached) engaged the Forward clutch. It seemed to me, that the success on that was driven by the fact, that I could move the lever further by hand, than it was moved by the shift cable.


I did also the measurements and found out, that travel way between neutral and forward compared to neutral and reverse are the same.


Then I adjusted the control cable a bit, so that the shift cable attachment stud fitted into the inner hole (before it was in the outer hole of the lever), while in neutral. However, I moved the lever within the 5 mm or so freedom way in neutral to the forward gear side threshold. Thus the lever is now being pulled a bit more into forward gear direction by the shift cable.


The result is a lot better now, however still not perfect. Now, the forward gear does still not engage, when I put the lever in the Cockpit just to forward idle. But it suddenly engages, when I push up the revs to, say 1500 and then go back to idle forward. In this moment it makes "click" and the clutch engages. As this process lasted up to a Minute before and is now back to 2 seconds, I can live with it, as long as it remains.


Any further comments? If not, thanks a lot for taking your time
Gipsy4