Trim leak down

[JDDsdogs]

2004 70TLRC short transom
No external leaks
Raises and lowers without issue
Oil level checked and is full, no air in system.

When the motor is trimmed up, the unit will slowly drop down till the lower unit is all the way down or touches the ground.
Like some check valve is worn or has a tiny bit of crud in it, preventing the valve from seating properly.
Through the service manual, I'm guessing the valve is in the Trim body as I don't see any valves, anywhere in the tilt cylinder. Am I on the right track here? If so, which valve is likely the culprit?
Thanks.

[99yam40]

the manual release would be my 1st thought

[robert graham]

My 1999 C90 Yamaha has always leaked down but very slowly, so I’ve never tried to get into it….guess the big question is how fast or slow does it leak down….always figured there was an o-ring or check valve just leaked a bit….

[JDDsdogs]

99yam40
Hadn't considered that, but might be a good place to start.

Robert,
Drops about 6 inches in approx 30 min. It might be a foible if the outdrive were not dropping down and blocking my side scan sonar.
PIB to have to go to the controls to raise it when in position to fish.
The motor is on a lighter boat that is effected by wind an current. Having the lower unit dragging in the water greatly improves the boats tracking while using the electric *****ing motor.
Keeping the motor raised to a point where it is out of the way of the side scan, yet in the water enough that it assists with tracking is the problem. I've got about 12" to play with.
I think its in a check valve system as well, question is, which one?

[TownsendsFJR1300]

Part #55: https://www.boats.net/catalog/yamaha...trim-tilt-assy



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[99yam40]

adding another remote switch to use where you are while fishing maybe the easiest thing to do if you cannot fix the leaking down.
some boats are rigged with a T&T switch at the bow of the boat when using a *****ing motor.
friend has one like that.
his dog will activate it sometimes when laying down at the bow, it can be a pain trying to figure out what is happening

[robert graham]

6 inches in 30 minutes seems like a pretty fast leak down….From what I’ve read about these tilt/trim units, there are special tools and knowledge required to repair them and I would seek out some professional help(Yamaha Technician) and pay for their expertise…..

[JDDsdogs]

Part #55: https://www.boats.net/catalog/yamaha...trim-tilt-assy



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Thinking maybe the o-rings as well. Thought about the the seats and adaptor1 too, but using the swag (scientific wild assed guess) method, that as long as the motor is raising and lowering smoothly at normal speed, they are probably not an issue.
Before I order, I think I will pull the assembly apart, inspect for physical damage and clean all the parts to the point that you could eat off them, reassemble, then see if its a fix.
If I can accomplish that without losing the dang little springs that go on both sides of the adaptor, "shouldn't" be to tough. :-)

Thanks for the insights guys, much appreciated.

[JDDsdogs]

6 inches in 30 minutes seems like a pretty fast leak down….From what I’ve read about these tilt/trim units, there are special tools and knowledge required to repair them and I would seek out some professional help(Yamaha Technician) and pay for their expertise…..

Have worked on heavy equipment hydraulics in the past, still have many of the tools I used back then. Like you suggest, may require specialized tools for the cylinders and elec/hydralic system. If I run into that I will reassemble and take it to a qualified tech. You offer sage advice none the less.

[robert graham]

There is a special spinner wrench tool to remove end caps….and there are some pretty darn good instructions and videos on the procedure that may be helpful. Good luck and keep us posted!….

[JDDsdogs]

There is a special spinner wrench tool to remove end caps….and there are some pretty darn good instructions and videos on the procedure that may be helpful. Good luck and keep us posted!….

Have spanners, but are for 4 to 6 inch diameter Heavy equip cylinders. I am guessing that the cylinders are not the issue as they are not leaking to the outside, oil level is not dropping and schematic does not show any check valves built into the base of the cylinders.
Will keep you posted but as to progress (or lack thereof), but it may be a bit. I don't have a heated shop, so I will wait till daytime temps get above freezing to take a shot at it. I'm old and my fingers don't work so hot when they are cold :-)
Likely will start a new thread like Trim leak down revisited.