Volvo FLYGMOTOR hydraulic drives

[lancsjohn]

Does anyone know what viscosity oil Volvo FLYGMOTOR type F10C-39 uses?
My 9m Catalac yacht as hydraulic drive system consisting of a 1600cc 4-cylinder diesel engine called SEARPANTHER directly driving an hydraulic pump which is piped to 2 hydraulic motors made by Volvo "VOLVOFLYGMOTORS type F10C-39 " via shuttle valves for forward and reverse. I do not know the pump make but think it is a gear pump.
I have been unable to find any information about the motors on the internet and Volvo have not replied to my email. Does anybody have a similar system? or know what hydraulic oil type these motors use?
The system was flooded with water so I have flushed the system with HLP46 hydraulic oil and got the motors turning but on full revs I only get 2 knot yacht speed and reducing the revs by half still gives 1.8 knots. the motors do work in forward and reverse. I would like to get 5 Knots if possible.
I will try to attach photos of pump. I am thinking of trying a lower viscosity oil 15 or 20 viscosity oil to see if this will increase the oil flow to the motors and increase the speed on full revs of the pump. do you think this will have any effect?

 

[scottie]

Try 01603714077 peachman Norfolk may still have staff with knowledge
Sea panther trade name for Watermota now defunct but lots of posts on here regarding them

 

[DownWest]

You also might try on a narrow boat forum, as hydraulic drives are not uncommon in them.

Thinking a bit more.. Try an agricultural suppler. Loads of pumps and motors used in that field. The fluid is quite thin, like ATF. You might be using something a bit viscous?

 

[penfold]

In the first instance have all filters been changed? Then if there are access ports temporary pressure gauges fitted to see whether the motors are receiving the pressure they need to give the ~10hp you'll need to get 5 knots. If there has been water ingress it may be the motors and/or the pump will need refurbishing.