2003 Johnson 50HP Power Trim/Tilt Assembly

HIdiver

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My 2-stroke engine will not tilt up without me physically assisting/pushing it up. I have to hold the tilt power button and push the motor up several times to get it in the fully tilted up position. The piston (0433225 Rod & Eye Assembly) holds the motor up as far as I've pushed it up each time. And there's no problem power tilting back down although its a little jerky when this is done. I filled the manifold assembly with hydraulic fluid and there is a leak where the piston enters the manifold cap. If I replace the piston 0-ring (0335143), would that seal the leak or would I need to replace other parts? And is there anything else I'd need to do (bleed the air out-how?) to make sure it works?
 

RRitt

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Re: 2003 Johnson 50HP Power Trim/Tilt Assembly

Assuming that it is properly topped off with fluid and that the motor is spinning then you probably have a bad check valve poppet or seat. It could be the MRV but people normally mention the mrv if they have messed with it. The MRV doesn't go bad if you don't use it. The leak around top needs to be fixed so that water does not get inside and cause rust. Neither the rod wiper nor the piston ring is the cause of your problem though. The rod wiper does not affect lift and the piston ring should last about 40 years. The piston ring is grossly over engineered wheras the check valves are grossly under engineered. It's probably the check valve poppets and/or seats.
 
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HIdiver

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Re: 2003 Johnson 50HP Power Trim/Tilt Assembly

Assuming that it is properly topped off with fluid and that the motor is spinning then you probably have a bad check valve poppet or seat. It could be the MRV but people normally mention the mrv if they have messed with it. The MRV doesn't go bad if you don't use it. The leak around top needs to be fixed so that water does not get inside and cause rust. Neither the rod wiper nor the piston ring is the cause of your problem though. The rod wiper does not affect lift and the piston ring should last about 40 years. The piston ring is grossly over engineered wheras the check valves are grossly under engineered. It's probably the check valve poppets and/or seats.

Thanks so much for the reply! Pardon my ignorance but what does MRV stand for? I haven't tinkered with anything so that couldn't be the problem, right? But how is the check valve poppet or seat which the diagram shows on each side near the bottom of the manifold assembly related to the leak at the manifold cap? If I replace the check valve poppets and seats, will this stop the leak? And do you know where I could order these parts at a reasonable price? We Hawaiians always get smashed by the shipping/handling costs. Aloha!
 

HIdiver

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Re: 2003 Johnson 50HP Power Trim/Tilt Assembly

Assuming that it is properly topped off with fluid and that the motor is spinning then you probably have a bad check valve poppet or seat. It could be the MRV but people normally mention the mrv if they have messed with it. The MRV doesn't go bad if you don't use it. The leak around top needs to be fixed so that water does not get inside and cause rust. Neither the rod wiper nor the piston ring is the cause of your problem though. The rod wiper does not affect lift and the piston ring should last about 40 years. The piston ring is grossly over engineered wheras the check valves are grossly under engineered. It's probably the check valve poppets and/or seats.

I had the power trim tilt repaired by a mobile mechanic and it was indeed the wiper, together with the backup ring and tilt rod seal. It had nothing to do with the check valve poppets or seats, which is why I had questioned that earlier.
 

RRitt

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Re: 2003 Johnson 50HP Power Trim/Tilt Assembly

I had the power trim tilt repaired by a mobile mechanic and it was indeed the wiper, together with the backup ring and tilt rod seal. It had nothing to do with the check valve poppets or seats, which is why I had questioned that earlier.

not possible. When lifting, all hydraulic pressure comes from underneath the piston. the shaft wiper and rod seal have nothing to do with lifting. you could remove them entirely and the system would still lift correctly. It would leave a puddle of oil and need to be refilled every single time but it would lift properly. If the problem is fixed then the mechanic stumbled across it while replacing wiper & upper seal.
 

HIdiver

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Re: 2003 Johnson 50HP Power Trim/Tilt Assembly

I don't agree that all hydraulic pressure comes from underneath the piston. I think pressure is maintained within the whole manifold assembly and the only leak occurred through the shaft wiper and rod seal which was the pressure leak. Your are right in that I could keep filling it and it would start to work better but I could see the oil keep leaking at the top of the manifold and the lift would start to fail rapidly.
 

RRitt

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Re: 2003 Johnson 50HP Power Trim/Tilt Assembly

The pressure does come from both directions but it alternates in accordance with whether you want to raise or lower the engine. There is an actuator and two check valves under the pump gears. When the motor spins "up" then the actuator opens the check valve that goes to topside of piston and fluid is allowed to drain freely back into reservoir. When the motor stops spinning then the actuator goes back to middle position and both checks valves are closed such that the fluid (and piston) are locked into place. vice versa for lowering.

When fully lowered, the piston shaft is immersed in oil. The displaced oil is held in reservoir. The reservoir has trapped air that compresses and expands to compensate as the piston shaft goes in and out. This may give the impression of pump pressure on both sides but has nothing to do with actual working pressure. A system with filler plug removed will still operate.

Problems raising are caused by either incorrect pressure beneath piston, fluid above piston not being allowed to drain, or mechanical jamming of mounting shafts or brackets. A fluid leak in cylinder cap could cause problems lowering but will have no possible effect upon lifting other than running out of fluid.
 
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HIdiver

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Re: 2003 Johnson 50HP Power Trim/Tilt Assembly

I agree with you, I've taken my boat out twice since being "repaired" and the second time, the power tilt started to fail. The power button would tilt the motor up at a slower pace and as soon as I let go the button, it wouldn't stay up and very slowly ended up in the full down position. I couldn't find any fluid leaks so what could be the problem? Do you still think it's a bad check valve poppet or seat and if yes, would this require removing the entire hydraulic lift assembly? The mechanic told me to check if the screw (?) that allows manual tilt up and down was loose and if it's not that, it's an internal valve problem that he's never worked on, and he would have to replace the entire hydraulic lift assembly. Do you know of any capable mechanics in Honolulu who could do the repair? And is it unsafe to use the motor in this condition?
Thanks for all your advice!
 

RRitt

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Re: 2003 Johnson 50HP Power Trim/Tilt Assembly

If your boat doesn't nose into the waves then I can't think of any reason operating w/o trim would be considered unsafe. It takes longer to get on plane, top speed is less, gas consumption is more, ride can be rougher, trailering can be a pain, etc. etc.

It is a little young to be having problems with your Manual Release Valve. If you use the MRV a lot and make it extra tight then the rubber tip or seat can wear out. When everything is perfect, you can actually feel the rubber tip make contact and just a small 1/10th turn gives you a solid seal. If you overtighten then the steel body can dig into the aluminum base and cut grooves. But since you put question marks after it then I assume you don't use it much and it shouldn't have any reason to be worn.

That would put the problem squarely back onto check valves. It is not such a good design. They used a new "miracle plastic" that could replace metal in certain situations. Same delrin type stuff they use to make plastic gears. But they did not design it with any orings. Orings work when compressed ffrom 10-20%. This means a system with orings does not have to have two perfectly round surfaces that exactly match. The rubber squeezes into shape like a gasket. It's meant to do that. The OMC design does not have any such give. The hydraulic pressure has to jam the plastic into a tapered hole with enough force to squash it into shape. During use, the poppet will rotate since it is basically a free floating piston. As it rotates the plastic is pushed and pulled at different stress points. It is not as good a design as other models and nobody has used the same technique before or since. It is not uncommon to see failures. In fact, failures are common enough that OMC ran out of inventory and no longer has any replacements to sell. As such, I would bet dollars to donuts that your check valves need replacing.

Rebuild Kit Evinrude Johnson Trim Tilt 25 35 40 48 50 HP 1989 2004 435567 | eBay
 
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