Stuck hydraulic for assisted tilt in 40hp

[johnyrude200]

I have a ’93 40hp, tiller motor where the assisted hydraulic is fully extended. I received the motor this way. I can manually force the piston back into the hydraulic cylinder, but it extends back out on it’s own with quite a bit of force. New setup for me (everyone gets a first time, right?)

Is there air in this hydraulic causing this, and if so, is there a bleeder somewhere for me to fix this?

[frankr]

Too new an antique for me, but there is a manual let-down valve. It may be open, allowing you to push it down. You should be able to pull it up as protection against damage when hitting a submerged object.

[johnyrude200]

quote FrankR:

Too new an antique for me…

Still has another 2 years to go before getting to the antique classification to the rest of the world! 😀

PS – JEALOUS of the warm weather in FL.

[fleetwin]

No way to bleed this system…
The problem is most likely in the tilt control cable and/or valve on the cylinder itself. You may be able to adjust the cable, sounds like the valve is stuck in the up position which allows you to tilt the engine. If slight adjustments make no difference, perhaps the cable is stuck/broken. Try removing the cable from the tilt cylinder valve/cap which should allow the valve to close holding the engine in position.
Seems like there is hope, cylinder is still charged and not stuck! These parts are ridiculously expensive, so try no to break them!

[johnyrude200]

For what it’s worth, I read the 1988 service manual section on this, and to say the least, it left quite a bit to the imagination. Nothing on concepts or principles of operation. Get ready for some VRO questions coming up soon (particularly bypassing the system…looks pretty simple…but what happens when the VRO/fuel pump craps out…).

Like frank said a long while back (perhaps this year, prior to the new forums), the service manuals (even the ones from the past 30 years) only tell you about 10% of what you need to know and assume you have training as a tech. I figured it was something simple but wanted to at least ask you guys before proceeding. I remember your advice on how the unit is quite expensive to replace in the post ’88 models and wanted to be extra cautious.

I will say that I am looking into a marine tech associates degree right now to make this an academically-backed career, and to relieve all of you from my constant barrage of classroom sophomore questions. I mean, I have a master’s degree in my prior career, but there is much to be said for formal schooling. That only goes so far, as experience is a true educator, but factual principles you learn in the classroom still discipline us all as practitioners.

I wrote an article in my previous career, about a decade ago, where I referred to it as the ‘hidden curriculum."

[fleetwin]

the 1988 manual won’t help you with this engine, you would need a 1989 or newer manual. The manual talks about adjusting "free play" in the cable. If there is no free play in the cable, or the cable is rusted/jammed, then the tilt cylinder valve may be held partially open which would result in the condition your report: being able to push the engine up and down, but it won’t hold/lock in any particular position. I suppose it is possible the tilt cylinder valve is rusted/jammed/corroded keeping it from closing completely as well. The theory is pretty simple here, but accessing/working on the tilt cylinder valve is a royal pain. Fortunately, you can move the engine up and down, so you should be able to access the cable connection to the tilt cylinder valve. Just be sure to prop the engine up somehow to make sure it doesn’t accidentally tilt down with your fingers trapped in there.

[johnyrude200]

Well as it stands right now, the motor is suspended in air by my newly acquired 2-ton engine hoist, so no safety concerns. I do have a 2000 service manual and will read it in the A.M. with great interest (thanks again Dan).

I figured that hanging the motor on my work stand would bring it to the normal position, but I picked up an ’86 model the same time I acquired this one and when I pulled it off the boat the hydraulic didn’t spring out, but it still made tilting the motor up for trailering easy.

This motor has been in storage for more than half a decade and appears to have been only gently used since it’s 1st owner, so I don’t think anything is stuck…other than my limited knowledge/experience with this minor aspect of it…

[dan-in-tn]

I thought I sent you a set of ’89 manuals? That would be the first year for this system. The cylinder is nitrogen filled for tilt assist as Don mentioned. Since it has a tendency to still go up that would mean some gas is still in it (a good sign)! The cables and routing were a real pain. If the cable has been replaced then there is a high probability it is out of adjustment. As a Don stated the valve must be fully closed for the engine to stay put. Good luck! Tight spaces inside the stern brackets on that model for adjustments.

Dan in TN

[Casey Lynn]

Your questions on the VRO system are easy.
Think of three pumps….all connected by a central stainless steel shaft.
The largest chamber houses the air motor, kind of an old school power brake booster arrangement with a large diaphragm that is moved in one direction by the vacuum and pressure pulses the engine produces. Check valves keep it moving in the same direction until it hits a stop which opens a flapper and the diaphragm is returned to the ready or start position to start the travel all over again. This scenario is for when the pump needs to supply a large amount of fuel and oil for very advanced throttle settings. Works a little different at low RPM/throttle settings but basically the same.
The central shaft also connects a second diaphragm in the second chamber. This is the fuel pump. It is huge compared to the small stand alone fuel pumps we normally talk about on here and really doesn’t work very hard to produce fuel for the smaller engines. Again a set of check valves allow the fuel in at the bottom and out at the top.
In the third chamber, also connected by the same central shaft, is an oil piston. There is lost motion built into the piston which allows the "Variable Ratio Oiling" or "VRO" This is a very short version of what goes on in the pump but the pump is pretty simple and makes an excellent stand alone fuel pump.

Should you want to disconnect the oil function simply disconnect the oil supply from the pump and close off the open hose with the supplied yellow plug. Disconnect all the wiring from the pump and the oil tank and you are done. Nice and simple.

[johnyrude200]

Thanks for the conceptual breakdown, and the practical bypass. Since we haven’t interacted much, basically when I decide to cut my teeth on a new family of motors, or a new generation, I usually pick up one that is a junker or needs a lot of love, and then a half dozen or more of them to get experience on after that one. Today was my first time seeing one in person, and in my own posession, and seeing the fuel, oil, and pressure in lines (from the crankcase) made me surmise from a conceptual point what you clearly explained. My question(s) would have been how the thing worked from a conceptual standpoint (which you explained really easily!!!!) and how the VRO ties into the alarm system, how I would disable/remove/disconnect that for obvious reasons (which you also answered, thanks again).

I mean, it’s a pretty clever piece of engineering several things together, but the risk of it failing and the potential catastrophic effects, all just to eliminate having to mix oil into gas doesn’t appeal to me. Although I can imagine the issue of customers just plain forgetting to mix oil into gas might have been the big reason behind this engineering addition. Either A), the customer is plain ignorant, or B) the friend borrowing the customer’s boat/motor is ignorant and ran it with straight gas.

My only other question about the VRO is how does that positively affect performance of the motor and/or improve longevity. This is one of my concerns on my 2014 Etec. Obviously that motor is direct-injected…everything….but what happens when the oil injection fails? I’m guessing the computer senses this and kills the motor off (it did when my 2-month old impeller decided to implode shortly after purchasing the motor for 6 large), but at WOT/5500 RPM, metal on metal is still bad combined with heat.

If I screw up the first one, I have basically nothing into it and I learn a ton. You guys basically save folks like myself a lot of time fumbling around to come up with a conclusion similar to yours, so thanks again for your willingness to share your knowledge and experience.

I picked up 2 of these yesterday (the ’93 40hp, and an ’86 50hp that has quite the story behind it…let’s just say 4 people almost died using it), and will be picking up a 3rd tomorrow (’81) which will hopefully be my main workhorse once I’m done going through the whole thing.

I have to ask, since I just went through (and still am to a certain level) the learning curve with the 25-30-35hp family…does this family of motors have any cooling system issues I should know about? From a very early observation standpoint, it seems like the same motor was made from the early 70’s right up through the mid-2000’s, albeit several revisions and enhancements. But they all look pretty similar. Would fit the build of the same progression the 25-30-35’s followed.

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