Volvo Mercruiser Trim Pump Conversion Swap

[bobb2003]

I have twin Volvo Penta Aquamatic AQ-290 outdrives were bleeding down in the up position. One of the drives had a leaking cylinder so I rebuilt the cylinders on both drives. This did not resolve issue with the drives leaking down from the up position. I then removed the check valve body assemblies and took them apart to find the single larger plunger type check valves had corrosion on both port and starboard apparently from a slight amount of water intrusion over the decades. I tried lapping them with some rubbing compound and it seemed solve the problem. Both the drives stayed in the up position for an extended period in the driveway. However they will not stay trimmed up after a minute or so under power. So I am considering converting to mercruiser type replacement pumps made by DB Electric. I like that I can buy rebuild kits with the check valves etc. from Sierra 18545A. Does anyone have experience or recommendations on doing this?

 

[Scott Danforth]

Both Mercruiser and Volvo Penta use oildyne 108 pumps
Just with different PRV settings

The sierra parts are knockoffs, not true oildyne.

The DB pump is also a knockoff

See your local hydraulic shop

My bet is you rolled the piston seal when you resealed them

BTDT and it means buying another seal kit just for the piston seals

Easy to test. Put drive up, pull rod side hoses, stand on drive. If oil comes out rod side ports, the piston seals are bypassing. if no oil, then it's the check valves

 

[Donald0039]

Sierra make quality aftermarket marine parts. I would not hesitate to use Sierra marine parts.

 

[QBhoy]

Is it the pump with the oil res built in ? Famous for the check valves passing and allowing the outdrive to not hold position.
Sometime in the early 90’s, VP changed the pump type to have the external oil res. You can retrofit this type fairly easily.

 

[Dillusion808]

My DB pump lasted all of 6 months before it started leaking around the pump and reservoir.

On the to do list to take apart and see if I can re-seal it. Hope its just an o ring.