Cheap "tilt assist" fix?

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 piston's 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 a particular situation.)


Although generally considered to be "unserviceable", I suspect that these units could indeed be serviced in the fashion I've suggested - 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 initial gas charge had just leaked down to the point that the motor became too heavy to manually tilt & therefore responded by hammering down its tilt assist release lever.

Very interesting.

No one on this or the other boating forum I've posted this thread on seems to know how OMC’s tilt assist cylinder is built - lots of reads though. However, if it's as I've assumed, it should relatively cheap/easy to fix & therefore profitable to anyone willing to attempt something different (EBAY/AMAZON sell 1/8 NPT shrader valves for ~$3 plus you'll need a half pint of generic hydraulic oil). Here’s how I would go about doing it:

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/N[SUB]2[/SUB] 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 think is 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 is getting a tank of N[SUB]2[/SUB] 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.

Being just a typical "customer", not someone who makes his living fixing motors or welding up battered aluminum props/boats, I don't have a tank of N2 or Ar to test out my own idea or much incentive to make that investment.

Here's another possible fix that doesn't require high pressure gas. Why not just vent the thing, refill with oil & connect its bottom vent to a manual oil pump scavenged from a $15 WALMART bottle jack with flexible brake line. The little pump could be mounted on the inside of the transom

These things fail (or at least mine did) because its initial gas charge leaked past the cylinder's internal seals - eliminating that gas would provide a permanent fix.

darrylsiemer said:

Being just a typical...

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I forgot to ask anyone who tries out this idea to let us all know how it works.

It is a plausible solution at list good enough to give it a try

bobbyc said:

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This thingy looks like a novel way of destroying a fiberglass engine cowling. Who makes it?

garelick....for motors up to 40 HP


https://www.google.com/#q=cabelas+motor+tilter

thanks again. The motor I'm working on is a Johnson 35 hP jet which means that it's a 50 hp both powerhead and weight wise. The back end of its cowling is already pretty badly bashed. It's really heavy - to check its lift cylinder's valve & cable (both OK) - I had to lift its bottom end with a comealong.

I'll probably buy a cheap little 2 ton hydraulic jack & see what it takes to rig its pump up to that cylinder.

update
I bought one of those little $12 WALMART bottle jacks yesterday - it's nicely made & works fine as a jack. But it can't be modified as I'd planned (I took it apart & something (oil reservoir) that should come off wouldn't ) so I went back to the internet & found someone selling 4 ton portapower jacks complete with oil reservoir and pressure hose for $35 - free shipping. I've ordered one - it's supposed to show up by the 13th.

It's me again. OMC has totally defeated me on this project. It turns out that they apparently "glued in" the 5/32" hex-headed set screws ( there are three, not two of them) that originally served as fill points for their tilt assist cylinder's nitrogen & oil. I broke a "fresh" Allen wrench and a hardened 1/4" drive hex bit trying to get one of them out. In other words, OMC deliberately made the this thing "unserviceable"

It's this kind of US engineering expertise & decision-making that makes me look forward to China's getting into the outboard motor business too. The "4 ton" Portapower jack showed up in 5 days & is,as usual with such stuff these days, both honestly and well made (serviceable).

I really appreciated the constructive comments.

PS has anyone ever succeeded in removing those set screws? How?

Thanks,

I'll have to take your word on this thing's having some sort of "impact protection" system because nothing I've been able to find either mentions it or describes how it might work. If it does and if it's not better thought out than is the rest of the gadget, I suspect that its use also renders the entire unit immediately "unservicable" from then on.

"Impact protection" on big motors is a fine sounding concept but isn't apt to prevent damage when you collide with anything hard & heavy when the boat's on plane...too much inertia.

My hydraulic jack brainstorm was foiled by the fact that OMC's engineering wizards apparently applied some sort of super loctite to the cylinder's gas/oil fill screws.

Thanks for the info. This whole thing started off with my posting a sketch of how I guessed the guts of the cylinder are built because OMC decided to keep everything secret. You are the first person that seems to know how it's actually built.

My points have to do with OMC's apparent attitude to its customers - it's not unique but it is why lots of people decided to swear off buying "made in America" stuff when the Japs & Germans started selling cars over here.. This thing is far more expensive that it should be, poorly engineered (you shouldn't expect high pressure gas to not leak past seals within a few years) & the thing could have been easily/cheaply rendered fixable by using brake bleeding screws instead of glued (welded?) in setscrews & putting a shrader valve in under the piston.

Again thanks.

Have you looked into putting a power trim tilt assy on it from a newer motor?

kimcrwbr1 said:

It takes a ...

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You shouldn't have to be a member of of the "one percent" to keep an old outboard motor running.

I've given up trying to fix it because 1) I've wasted too much time on it already, 2) it actually belongs to a friend of mine, not me, & 3) if we really need to tilt the thing up, it's possible to pull over into the shallows, one of us get out of the boat & pull it up by hand after which the guy still in the boat closes the "tilt" valve/lever.