Outdrive slowly comes down under power

[hansoloalaska]

Ive got a Volvo penta 570A, year 1991. Its attached to a duo prop outdrive.

My problem is the drive goes down under power. I take off at cruise speed set at -4. A minute or two goes by, I look down, its -5. Another two minutes, and its -6. You get the idea. I have to contantly watch it and adjust back up.

Ive got good looking oil in the pump resorvior. Not miky or anything. I guess you wouldnt see water with an internal leak though.

Are my cylenders shot? Anyone ever take em off and rebuild em? Also there has to be some check valves in the hydralic system. Anyone know where?

Anyone had this problem?

Thanks!

 

[Don S]

Re: Outdrive slowly comes down under power

I have found that about 99% of the time the problem is in the pump, not the cylinders. There are check valves and 3 relief valves in the pump. The check valves are non replaceable, and the high pressure relief valve is replaceable. Sort of a trial and error repair with the relief valve if you want to try that.
There are no kits or repair parts for the cylinders from Volvo, just replacements.
Volvo doesn't have any troubleshooting info on the trim pumps, I use the Mercruser trim pump test manifold to pressure check and to determine if the pump or cylinders are at fault.
Not much help, but here is a link to the OEM service manual with what little info there is on it.
http://www.4shared.com/account/file...o_DP-C_Drive_manual.html?sId=TrunkGZ8S7oDyNOO