3QM30 No Reverse

[kiwibob]

Our yanmar will go into forward and reverse faultlessly when the engine is cold but when the engine is hot we can only get forward!!
I have checked the control arm on the gear box and the morse cable all appear to be tight and with the correct amount of distance travel, there is oil in the box.
Sometimes after putting the lever into forward and reverse a few times and altering the revs of the motor at the same time it will suddenly go in but it's no guarantee.
All suggestions welcome as it makes for a harrowing re-entry in to the marina with a tail wind.
The vessel is a Tayana 37.

[ShaunJ]

Welcome to CF kiwibob
How old is the gear box

If you can manually shift it and feel it move all the way in reverse and it doesn't shift, it may need to be looked at.

[kiwibob]

I believe the engine and gear box may be 30 years old and I don't know of any previous work done but it runs sweet.I can manually put the lever on top of the box into reverse position but it doesn't engage unless cold.
Engine has around 3000 hours on the clock.

[Alasdair]

The 3QM30 model with YP10-M Gearbox has an ajustable clutch pressure bolt on top of the box behind the gear lever. Your reverse pressure may need adjustment. If you have the later 3QM30H with the KH18 Gearbox I dont think these are adjustable. I have both the Operation and Service Manuals I can email to you if you need them.

[kiwibob]

Originally Posted by kiwibob

Our yanmar will go into forward and reverse faultlessly when the engine is cold but when the engine is hot we can only get forward!!
I have checked the control arm on the gear box and the morse cable all appear to be tight and with the correct amount of distance travel, there is oil in the box.
Sometimes after putting the lever into forward and reverse a few times and altering the revs of the motor at the same time it will suddenly go in but it's no guarantee.
All suggestions welcome as it makes for a harrowing re-entry in to the marina with a tail wind.
The vessel is a Tayana 37.

I have the kh18 box so no adjustment have a manual on board so will dig it out this weekend and see if I can solve the problem.

[kiwibob]

Solved the problem by changing the transmission fluid.
The oil that came out was quite thick and didn't smell like auto transfer fluid does, put in the factory recommended fluid and it now work great, thanks to all for your advice.