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500B DP Outdrive raises while in forward

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whatsss_uuuppp

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I have twin drives on a 1991 houseboat that is new to me. The port drive seems to operate at speed fine. The starboard drive indicates it is triming up and flashes red when I go beyond about 2200 RPM's. Being new to Volvo I am not understanding the core of the issue, which I want to do before contacting a service center. I know reverse on some of these drives has been an issue in the past... but that does not seem to be an issue currently.
 
whatsss_uuuppp said:
I have twin drives on a 1991 houseboat that is new to me. The port drive seems to operate at speed fine. The starboard drive indicates it is triming up and flashes red when I go beyond about 2200 RPM's. Being new to Volvo I am not understanding the core of the issue, which I want to do before contacting a service center. I know reverse on some of these drives has been an issue in the past... but that does not seem to be an issue currently.
Click to expand...

Ayuh,... Is the drive actually risin' up, or is it just the gauge is screwy,..??
 
bondo said:
Ayuh,... Is the drive actually risin' up, or is it just the gauge is screwy,..??
Click to expand...

Valid question... Best I can tell it's actually risin' up as the port motor will over power the starboard and force boat starbaord if I try and go higher RPM's. As long as the trim indicator stayed in the green, I could stay straight and steer with the wheel. Also seemed like RPM's on Starboard would rev more as well when tried to go higher as further indication of cavitating (?) or loss of resistance.

At the lower RPM's and in reverse the drive seems to work fine and I can use to differential steer as needed.
 
This is a very long shot, but easy to try... There is a remote possibility that your stbd drive is actually in reverse when you think its in fwd.. On a hull of your type, reverse propulsion will be less efficient than forward, and the port drive will over power the reduced drive capability of the Stbd drive while is actually in reverse (therby moving the boat forward) until reverse thrust on the stbd drive (with interlock in wrong position) causes the drive to lift up.

A simple test would be to leave the port motor in neutral and slowly power up to stbd drive until the boat just starts to move and the see which direction the boat moves.

If that is not the problem, you likely have a FUBAR in the electrical controls to the trim/lift on the stbd drive.


Also, my usual question... How long have you had this problem/boat? "I know you said this was a "new to you boat", but did it ever work OK? ifso, what work was done recently?
 
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Thanks Capt Bob. At lower RPM's the drive is usable and reacts as expected. My understanding, the boat was hauled last fall and both drives serviced with bellows etc... Shame on me as also during our sea trail we never took it out of the harbor as log jam prevented safe operation... so it's hard to know if the issue is preexisting or something I somehow caused.
As trim( an obviously tilt) are not really ever needed in my scenario.... is it possible to lock them into one position?
 
1991 Volvo 500B dual prop manual.JPG
 
At the MarinePartsEurope site, I do not see a 500B, only a 500A listed.
http://www.marinepartseurope.com/en/volvo-penta-schematics-MarineGasolineEngines.aspx

If you consider that this is a 1991 stern drive, it will be in the 290 family, even if labeled SP or DPA.
The 290 uses the anchorage bracket for the cylinder attachment.
This system also maintains a version of the reverse latch unit, also being used for impact break-a-way purposes.
10075.jpg

The later drives omited the anchorage bracket and latch system in lieu of a direct suspension fork connection.

Even at that, the drive should not raise on it's own while powering in forward.
The hydraulic cylinder pump would need to be activated in order to raise the drive.

Simple tests:

disconnect the hydraulic pump harness at the pump and test to see if the drive is raising.

disconnect the trim switch and test to see if the drive is raising.

with the drive in the fully down position, tightly secure a wire to the base side of the cylinder, extend the wire along the length of the cylinder, and gently secure the AFT end of the wire to the stem end.
test drive the boat. if the wire has slipped and been pulled on at the stem end, then that would indicate that the cylinders are indeed extending.
if the wire has not slipped, then the cylinders have not been extending.

10317.jpg


Side notes:

1.... With both drives being DP's, you'll be running both of them from the transmission's lower driven gear.
This means that a FWD shift will rotate the eccentric piston CW, dropping the shift shoe down and engaging the lower driven gear.

2.... A FWD shift will always extend the shift cable at the gear yoke (SEQ # 2 in the first schematic).



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