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470 merc, alpha one, wont go down

C

csmith1973

New member
Hello everybody.
I just got a boat, and it has a 470 mercruiser with an Alpha one drive. It will not lower. I disconnected the pistons to see if the drive was hung up, but it was not. The motor will extend the pistons, but when I push down, the pump runs, but it sounds like it is airbound. It sounds completely different. It is running fast, but not really pushing fluid. Any ideas where to start? This is my first Mercruiser.
 
The oil level is full, and the pistons are extended. the boat sat with the drive up for over a year, BUT the pistons look like they are in excellant shape.
 
There jamed from being left extended, you should always relieve the pressure but tapping the down button once extended.
Might try have someone stand/jump on the drive while trying to lower it
Remove the rams and use a press to retract them
 
The oil reservior fill cap needs to be open 3/4 turn. Since the OD was left up for a long time the bellows have taken a set. They will probably crack, split or tear allowing water into the boat and drive shaft. Look closely at them for fine cracks or dry rot. Replace them along w/the water inlet hose so you don't sink the boat.
 
csmith1973 said:
Hello everybody.
I just got a boat, and it has a 470 mercruiser with an Alpha one drive. It will not lower. I disconnected the pistons to see if the drive was hung up, but it was not. The motor will extend the pistons, but when I push down, the pump runs, but it sounds like it is airbound. It sounds completely different. It is running fast, but not really pushing fluid. Any ideas where to start? This is my first Mercruiser.
Click to expand...

the outdrive piston pump oil filling is to be done with these pistons fully retracted...when you hit the down button does the pump run ? If not this may be the switch or at the pump the connections to it..


to bleed the system disconnect the pistons from the drive . allow to hang vertical..work the piston in/out. when fully in closed/full in check for oil level..
 
Yes, the motor does run when the down switch is pushed. After looking at some diagrams, I am thinking it may be the valve block. There appears to be a piston that goes back and forth. Could it be stuck to one side?
 
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