Darryl Siemer
08-29-2016, 02:53 PM
Since the problem that this thread addresses has been the subject of much discussion on this forum, I've decided to post it here too.
I’ve sketched up my guess (ATTACHED) of the internals of the notoriously problematic “tilt assist” lift cylinder that came standard with many 30-50 hp 1990-2005 JOHNRUDEs (part no. 0434037, list price $625.99). I’ve assumed that it’s basically just a little bottle jack with some high pressure gas (nitrogen) trapped under its piston and hydraulic oil above it. That oil is pushed into the surrounding outside chamber when the piston is raised (motor manually lifted) and the valve connecting the top of the cylinder to the bottom of the latter is “open” (the lever at the motor’s passenger side pushed backwards).
Questions:
1) Is this how it’s really plumbed?
2) If “no”, how is it configured?
3) If “yes”, why wouldn’t the substitution of a 1/8” NPT shrader valve (cheap, about $3) for the plug in its bottom “fill port” fix most of the problems experienced with it? (doing so would permit a mechanic to easily replenish the nitrogen which inevitably slowly leaks past the seals of such things –it would also allow him/her to tailor the degree of “assist” provided to particular situations.)
Although generally considered "unserviceable" I suspect that these units could indeed be serviced as suggested below- there's nothing magic about gas charged shock absorbers & one tank of nitrogen (or argon) could recharge hundreds of them. The real difficulty is that no one outside of OMC seems to know how this particular gadget was built & it's been unwilling to divulge that info.
I also suspect that the reason so many actuator cables failed is that motor owners assumed that valves were "stuck" when the original gas charge had leaked down to the point that the motor became too heavy to manually tilt & therefore responded by hammering down its tilt assist release lever.
No one on either of the other forums I've posted this thing on seems to know exactly how that cylinder is built either - lots of reads though. However, if it's as I've assumed, it should relatively cheap/easy to fix -EBAY/AMAZON sell 1/8 NPT shrader valves for ~$3 plus you'll need a half pint of generic hydraulic oil. Here’s what I'd do:
1) release the motor’s tilt assist (move the lever stern-wise) and “ muscle” its lower end all the way up & tie its power head to the boat’s bow/seat so it can't fall back. Then carefully crack open the trim assist cylinder's upper plug screw to release gas that has gotten past the piston’s seals. Since such gas is likely to have pressurized the outside reservoir, most of the hydraulic oil –approximately one half pint - is apt to be lost as well (much less would be lost if the cylinder were to be removed from the motor and turned upside down before that screw is removed). Inject approximately the same amount of fresh oil back into that opening with a syringe, apply gasket sealer to its plug screw, and screw it back in. (An additional engineering improvement to OMC’s system would be to add a tiny gas vent at the top of its outside reservoir to prevent such reverse pressurization. Its opening would also provide a more convenient oil fill point – a $626 gas-filled bottle jack should be “maintainable”.)
2) carefully remove the lower plug screw (there's almost certainly still some fairly high pressure gas left under the piston)
3) if that hole isn't already threaded for your shrader valve, do so (most tap/die sets include the necessary tap). If it’s necessary to ream it out first, use a 11/32” drill.
4) apply gasket sealer to that valve’s threaded end & screw it in tight
5) pressurize the cylinder with argon or nitrogen until it's able to hold the motor up by itself (i.e., put some slack into your tie-off rope). This will probably require over 300 psi –beyond the upper range of most gas regulators - which likely means that your fill hose will have to be connected directly to the Ar/N2 tank’s valve - “tweak” the latter to pressurize.
6) untie the rope & repeatedly tap the shrader valve's sealing pin until enough pressure escapes to allow the motor to completely settle down under its own weight.
7) Test for leaks by tilting the motor back up, locking it by moving its tilt assist lever all the way forward, and putting soap solution on the cylinder’s valves & seals – if you don’t see bubbles & the motor stays put, you’ve fixed it.
8) charge whatever you feel to be fair but please tell your customer that your next fix is apt to be both quicker and cheaper.
The really "tough" part about this for a non professional like me is getting a tank of N2 or Ar to pressurize with; however, anyone with MIG/TIG (aluminum) welding capability probably already has it.
If anyone decides to give this a shot, please let us know how it worked out.
I’ve sketched up my guess (ATTACHED) of the internals of the notoriously problematic “tilt assist” lift cylinder that came standard with many 30-50 hp 1990-2005 JOHNRUDEs (part no. 0434037, list price $625.99). I’ve assumed that it’s basically just a little bottle jack with some high pressure gas (nitrogen) trapped under its piston and hydraulic oil above it. That oil is pushed into the surrounding outside chamber when the piston is raised (motor manually lifted) and the valve connecting the top of the cylinder to the bottom of the latter is “open” (the lever at the motor’s passenger side pushed backwards).
Questions:
1) Is this how it’s really plumbed?
2) If “no”, how is it configured?
3) If “yes”, why wouldn’t the substitution of a 1/8” NPT shrader valve (cheap, about $3) for the plug in its bottom “fill port” fix most of the problems experienced with it? (doing so would permit a mechanic to easily replenish the nitrogen which inevitably slowly leaks past the seals of such things –it would also allow him/her to tailor the degree of “assist” provided to particular situations.)
Although generally considered "unserviceable" I suspect that these units could indeed be serviced as suggested below- there's nothing magic about gas charged shock absorbers & one tank of nitrogen (or argon) could recharge hundreds of them. The real difficulty is that no one outside of OMC seems to know how this particular gadget was built & it's been unwilling to divulge that info.
I also suspect that the reason so many actuator cables failed is that motor owners assumed that valves were "stuck" when the original gas charge had leaked down to the point that the motor became too heavy to manually tilt & therefore responded by hammering down its tilt assist release lever.
No one on either of the other forums I've posted this thing on seems to know exactly how that cylinder is built either - lots of reads though. However, if it's as I've assumed, it should relatively cheap/easy to fix -EBAY/AMAZON sell 1/8 NPT shrader valves for ~$3 plus you'll need a half pint of generic hydraulic oil. Here’s what I'd do:
1) release the motor’s tilt assist (move the lever stern-wise) and “ muscle” its lower end all the way up & tie its power head to the boat’s bow/seat so it can't fall back. Then carefully crack open the trim assist cylinder's upper plug screw to release gas that has gotten past the piston’s seals. Since such gas is likely to have pressurized the outside reservoir, most of the hydraulic oil –approximately one half pint - is apt to be lost as well (much less would be lost if the cylinder were to be removed from the motor and turned upside down before that screw is removed). Inject approximately the same amount of fresh oil back into that opening with a syringe, apply gasket sealer to its plug screw, and screw it back in. (An additional engineering improvement to OMC’s system would be to add a tiny gas vent at the top of its outside reservoir to prevent such reverse pressurization. Its opening would also provide a more convenient oil fill point – a $626 gas-filled bottle jack should be “maintainable”.)
2) carefully remove the lower plug screw (there's almost certainly still some fairly high pressure gas left under the piston)
3) if that hole isn't already threaded for your shrader valve, do so (most tap/die sets include the necessary tap). If it’s necessary to ream it out first, use a 11/32” drill.
4) apply gasket sealer to that valve’s threaded end & screw it in tight
5) pressurize the cylinder with argon or nitrogen until it's able to hold the motor up by itself (i.e., put some slack into your tie-off rope). This will probably require over 300 psi –beyond the upper range of most gas regulators - which likely means that your fill hose will have to be connected directly to the Ar/N2 tank’s valve - “tweak” the latter to pressurize.
6) untie the rope & repeatedly tap the shrader valve's sealing pin until enough pressure escapes to allow the motor to completely settle down under its own weight.
7) Test for leaks by tilting the motor back up, locking it by moving its tilt assist lever all the way forward, and putting soap solution on the cylinder’s valves & seals – if you don’t see bubbles & the motor stays put, you’ve fixed it.
8) charge whatever you feel to be fair but please tell your customer that your next fix is apt to be both quicker and cheaper.
The really "tough" part about this for a non professional like me is getting a tank of N2 or Ar to pressurize with; however, anyone with MIG/TIG (aluminum) welding capability probably already has it.
If anyone decides to give this a shot, please let us know how it worked out.