Trim pump heat issue? OD creeps up over time while sitting on trailer

[eric102]

I normally keep my Bravo 2 OD in the down position when the boat is sitting on the trailer. But over time it will gradually creep up, maybe a couple inches per week at the most in the hot weather. I'm assuming its heat related as the OD gets a lot of sun where the trailer is parked, the battery power switch is off.

I recently replaced the thermal relief valve in the trim pump because that had cured the same problem about 15 years ago, didn't fix it this time

Could it be the up or down pressure relief valves in the pump? Or something else?

The pump oil was perfectly clean and its never had any water in it but it is 27 years old. The up and down pressure relief valves are original.

 

[wellcraft-classic210]

Are you saying it moves in the up or down direction from the ground when on your trailer ?

If its down Its likely a little bit of leakage in your valve body from dirt or wear

If its up -- HMMM no idea as fluid expansion should not normally be noticeable.

 

[harringtondav]

If its up -- HMMM no idea as fluid expansion should not normally be noticeable.

I was thinking the same about the oil changing volume much with temperature. Is your trim reservoir's cap vent working? Maybe the change in air temp is causing the reservoir to pressurize and give the oil a little more push. That's a guess if you haven't noticed.

 

[KJM]

i'd try an exorcism if it was me, ....just sayin'

 

[eric102]

Are you saying it moves in the up or down direction from the ground when on your trailer ?

If its down Its likely a little bit of leakage in your valve body from dirt or wear

If its up -- HMMM no idea as fluid expansion should not normally be noticeable.

Yep it moves up from the ground which makes me suspect the up pressure relief valve is allowing a slight amount of oil to sneak by. It never leaks back down so I'm guessing the down valve is OK.

 

[eric102]

I was thinking the same about the oil changing volume much with temperature. Is your trim reservoir's cap vent working? Maybe the change in air temp is causing the reservoir to pressurize and give the oil a little more push. That's a guess if you haven't noticed.

The cap vent is fine and the pump itself stays fairly cool inside the boats hull compared to the solar heat the black OD and cylinders probably soak up in the direct sunlight. The boat (except for the OD) is mostly covered with a silver tarp.

 

[eric102]

i'd try an exorcism if it was me, ....just sayin'

I'll give it a try

 

[harringtondav]

Yep it moves up from the ground which makes me suspect the up pressure relief valve is allowing a slight amount of oil to sneak by. It never leaks back down so I'm guessing the down valve is OK.

I understand the up circuit operates at a higher pressure (+- 2000 psi) than the down (+- 300 psi (?)). So the heat expanded/driven oil could overcome the up circuit's relief valve. Still guessing here. Also guessing is maybe a check valve is allowing the cooling up side of the cyl. to replenish itself, and continue the process the next hot day.

Not trying to be cute, but if this is your largest problem with your boat, trim it down to de-stress your bellows as needed, and boat on.

 

[wellcraft-classic210]

Its getting lighter -- must be a helium leak from an alien space craft in your parking area :sleeping:

 

[achris]

By all the laws of physics and hydraulics, what you are reporting CAN NOT happen...

The Bravo 2 drive weights a substantial amount, about 150lbs.. To lift that drive with a 2" ram, you would need a pressure on the UP side of the piston of around 44psi, about 3-1/2 atmospheres. As there are 2 rams, we can halve that, about 22psi, 1-1/3 atmospheres. So we can discount air pressure, as that can exert a pressure no more than 14.7psi (1 atmosphere). So heating and cooling of the oil, even with the UP relief valve jammed shut, with the best will in the world, could only produce about 2/3 of what's required.... And even if it were, it would drop back down when the oil cooled. You appear to have something that is making energy from nothing. I'd love a piece of that!

Obviously this is happening, because you are seeing it... I am curious, and am so tempted to just get on an aeroplane to have a look at this myself!

As for a reason... I've got nothing...

Chris.........

 

[eric102]

Another observation, after being in the sun all day I felt the metal part of the oil lines at the pump inlets and they were cool to the touch, probably air temperature. I was kind of expecting one of them to be warmer than the other.

Now I'm starting to think maybe its something in the cylinders? Its probably been 10 years since I last rebuilt them but very low hours of actual use.

And yes I know its a small problem but I'm a bit OCD when it comes to problem solving

Keep the guesses coming!

 

[achris]

...And yes I know its a small problem but I'm a bit OCD when it comes to problem solving...

Me too.

Ok, let's do some testing...
When you trim the drive all the way up, does the pump load up hard if you don't stop immediately? And going down, the pump should 'freewheel' a lot easier... Stops going down (as it's reached a mechanical hardstop) but the pump sound isn't as different as when it loads up when it reaches the top.

This may point us to an area to check, pump/rams/anti-gav generator from your space craft.

Chris.......

 

[eric102]

Me too.

Ok, let's do some testing...
When you trim the drive all the way up, does the pump load up hard if you don't stop immediately? And going down, the pump should 'freewheel' a lot easier... Stops going down (as it's reached a mechanical hardstop) but the pump sound isn't as different as when it loads up when it reaches the top.

This may point us to an area to check, pump/rams/anti-gav generator from your space craft.

Chris.......

Yes to both, pump sounds normal at both stops.

One thing I haven't mentioned is if I haven't cycled the drive up and down for a few months (after it has magically risen on its own) there appears to be a little bit of air in the system on the up or down side, don't remember which. No external oil leaks anywhere.

 

[achris]

Does it raise all the way to full UP? (if you don't touch it)

 

[eric102]

Does it raise all the way to full UP? (if you don't touch it)

Pretty close if not all the way up this winter and spring when I hadn't been in the boat for that period.

 

[achris]

Do you live in the Bermuda triangle?

 

[eric102]

Do you live in the Bermuda triangle?

I wish it were that simple. I wonder if Puget Sound has a triangle? Or is it global warming?

 

[eric102]

I had a chance to spend a few more hours on it today and came up with some new observations, not sure what they mean though.

1) From the fully tucked in position the OD rams have moved about 3/16 of an inch in 3 or 4 days of partly sunny weather, temps in the 70's and 80's.

2) With the battery switch off I'm still getting 0.14 volts to the 110 amp trim pump fuse. The trim pump gets its juice from the starter motor which is supplied by the battery switch. No measurable voltage is getting through the solenoids to pump itself unless its intermittent.

3) Found a little bit of oil on the bottom of the Mercathode unit which is under the OD hydraulic manifold. Looks like maybe a few drops have fallen on the crushed rock directly under it over the last couple months since the boat was last moved. The trim pump oil level has never really varied from the full mark so I don't think its leaking much. I put a piece of plywood under the OD to see how much if any oil drips out over the next few days.

I disconnected the power to the trim pump to see if the 0.14 volts could possibly be the culprit. I'm guessing the voltage has something to do with the Mercathode (which is always on) or could it be something else? Will know more in a few days.

Even if 0.14 volts was getting to the trim pump motor would that be enough to turn it at all?

Could a cracked or leaky hydraulic manifold cause the OD to rise through solar heating?

Lots of questions but no answers as usual.

 

[achris]

I still got nothing. :facepalm:

Solar heating wouldn't account for it. I have an Alpha drive, same trim system, and it lives in a garage that on a hot day can get over 110, and my drive doesn't move, at all....

0.14v is not enough to spin the pump motor. I have my batteries always ON, as I have a charger plugged in. The trim system has 12v available at all times.

A leaking hydraulic manifold would see the drive DROP, not raise.

Chris......

 

[eric102]

Fixed? maybe?

Yesterday I pulled both trim cylinder rods, disassembled and cleaned the shock valves and installed new O-rings on the shock valve pistons (had a couple of spares from a previous end cap rebuild). Didn't pull out the floating pistons since I only had 2 new O-rings and figured what the heck might as well start somewhere with the parts I had before buying more rebuild or reseal kits.

So far it seems to be fixed after being in the sun all day, zero movement. Don't know if the O-rings did it or a shock valve ball bearing might have been leaking, both looked fine before disassembly.

I'll know for sure if it doesn't move for several more days.

A cheap fix so far