Locking the tilt on your outboard

[Sea Isle Salty Dog]

My boat partner locks the tilt on our Yamaha 250 after each use. I understand the need for this when trailering, but I am not sure this is a good practice on the mooring. I think the idea is to unload the hyraulics, but I am not sure it is necessary. Anyone have any advice on this? Thanks.

[BigWillJ]

Can't help you with the mooring, but can share this trouble free experience.

For trailering, we "lock" our 200 Yammy in the up position, but retract the tilt/trim posts while the motor is in that position.

When parked at home, we lower the motor to full down position, thus also retracting the tilt/trim posts to a full inward position.

Again, don't know about mooring, or possible corrosion factors in that setting, nor can I speak to "unloading the hydraulics", but we haven't had a problem with our hydraulic tilt/trim in 16 years of doing it the way I described here.

[Spearo]

For trailering my 225 hp I just bring it up enough but never all the way up and locked. When on the dock I make sure the hole thing is out of the water but never locked. When I'm on the road I rather not have the hole thing up and locked creating more stress on the stern every time you hit a bump.

[matey]

sea isle, i see nothing wrong with locking it at mooring. it might help take some strain off the hydraulics while up. it you want to try don't lockitone time and see if it doesn't drift down some over a period of time. at least locking will stop this.

[BigWillJ]

Spearo originally wrote:
For trailering my 225 hp I just bring it up enough but never all the way up and locked. When on the dock I make sure the hole thing is out of the water but never locked. When I'm on the road I rather not have the hole thing up and locked creating more stress on the stern every time you hit a bump.

Spearo - I'm not sure I understand that stress theory, based on the position of motor when trailering?? Certainly never been a problem here.

[uncljohn]

I never locked mine in the past 3 years I've had the boat, and I don't believe the original owner did either, and now after 18 years the hydraulic tilt cylinder won't hold the engine (200 Yam) upright. W/in a few hours it eases back down into the water, so I'm now lashing my outboard in the up position.

And the locks are all rusted on my engine, so I couldn't engage them if I wanted to. So, I'd say the moral of the story is to lock. Which I will do religiously w/ my next engine.

[Spearo]

My personal belive is that there is more stress on the transom when trailering when the OB is exteded out (or up) 100% and not supported back down to the trailer frame in some way. The best way to see this is by driving close bihind a boat been towed with motor all out and no supported. If you ever go looking for a use boats with OBs this area will tell the hole story just by looking at it and I'm sure that the sale person will tell you "Oh, that's just the jellcoat" yeah sure! I'm not an expert but I had boats since the mid 60's and have always supported my lower unit before hitting the road and I never had to this day cracks around this area.

[BigWillJ]

Thanks Spearo. You appear to have been around as long as me, so you probably would agree that the topic of trailering with an o/b up or down has been, still could be, and apparently always will be, debated until the cows come home. All the research and questions I've asked over those many years on this very subject, and more recently - internet searches, have yet to produce a definitive answer one way or the other. I suspect it has more to do with the type or quality or setup of the boat and motor package than it does with whether a motor should be trailered one way or the other.

I apologize to Salty for the topic getting away from a locked motor while moored, and the matter of hydraulics, but I had to ask about that stress theory. So thanks again.

I'll add this for Salty - just checked the book on my 200 Yammie trim/tilt, and here's what it said verbatum - "The power trim/tilt system will temporarily maintain the engine at any angle within its range to allow shallow water operation at slow speed, launching, beaching or trailering". That tells me my motor should be all the way down, or locked all the way up, thus NOT (permanently) resting on the tilt/trim system while in storage or at mooring.

[Sea Isle Salty Dog]

Thanks to you guys for all this great info and experience (the real knowledge).

Spearo, as a degreed, but no longer practicing, mechanical engineer, I agree with you 100% about the stress on the transom. The "moment arm" (or leverage) of the motor in the up position produces a larger rotational force (think about a longer wrench requiring less force from the mechanic to turn a bolt) on the transom. The question is whether today's transoms are stronger and maybe unaffected by this.

As far as the hydraulics go, I am just not current on the latest strengths and weaknesses of today's designs. The transient stresses on the hydraulics that are created while trailering are significant, thus making me think unloading the hydraulics while trailering (using the lock) will help avoid blowing a seal or creating a leaking seal. However, on the mooring, I would not expect those stresses like trailering over bumps at 55MPH and might think that the load actually helps to maintain a good seal, but I am really speculating now....[smile]

[BigWillJ]

Sea Isle Salty Dog originally wrote:
...The question is whether today's transoms are stronger and maybe unaffected by this.....

Exactly, and more....

Do an internet search and you'll find enough debate on this to keep one busy for awhile.

Even the "pros", boat and motor dealers, and manufacturers don't all agree. And physics and engineering get called into play all the time, still with little agreement.

Quite possibly, you'll glean from all that debate that transoms are designed to endure many more forces when operated over water vs. when trailered. A ride over a bumpy road is cake walk compared to a ride over water, even smooth water. Makes little difference whether it's rotational or vertical forces. Might make a difference if it's a "smaller" motor, which can't be locked down, clamped to a less than forgiving transom on a "small" boat (thus the debate over those so-called "transom savers"), but it's a whole different game with a thru-bolted motor on a transom designed for such, add to that a power tilt/trim system.

Show me the latter with a transom that can't take the forces of trailering a motor up or down, and I'll show you a boat you shouldn't buy in today's market.

[Seahunter]

As for the hydraulics system, I've torn a few of them down in my days and most are typically 1.75 or 2" bores which utilize multiple o-rings with backing rings so the weight of an outboard in pretty insignificant to the design of the tilt assembly. There is also an internal pressure relief valve built into the cylinders so your chances of you damaging a ram or blowing a seal are next to impossible.

Over time the system will start to leak down but this is usually do to the seals on the directional control valve going bad, not the o-rings on the cylinders themselves going south..

[BigWillJ]

Seahunter originally wrote:
.....Over time the system will start to leak down but this is usually do to the seals on the directional control valve going bad, not the o-rings on the cylinders themselves going south..

Great input Seahunter, thanks!

What causes those seals to go bad over time?....simply age?

Can a driveway mechanic repair/replace them?

Also, can you suggest an answer to whether an outboard should "rest" upon extended trim/tilt rods when boat is parked, stored, or moored between periods of use?

Thanks a bunch.

[Seahunter]

The most common cause of seal failures are:
1. The use of an incompatible fluid which causes softness and swelling of the seals.
2. Moisture intrusion typically results in internal corrosion and pitting of the sealing surfaces which is detrimental to integrity of the sealing surfaces.
3. And last but not least, dry rot from lack of use.

Of the three, I would venture to guess that moisture is to blame for most premature failures in the marine environment. Moisture can be introduced to the system by a loose fitting reservoir cap, a leaky fitting in the vacuum side of the system, a leaking shaft seal and a multitude of other ways. Although not recommend in the manuals, I would recommend changing out the hydraulic fluid (automatic transmission fluid in most cases) every other year or so as preventative maintenance. Most systems are self purging so changing the fluid involves nothing more than draining the system and replacing the fluid and running the cylinders up and down a few times to purge the air from the system.

The thing that’s most over looked in the system is the shuttle valve or directional control value as it more commonly referred. This valve is typically internal to pump assembly and its job to rout the pressurized hydraulic fluid to the different ports on the hydraulic cylinder with the center position being used to hold equilibrium in the cylinder, meaning to hold the cylinder in place. It’s the seals in this assembly that typically causes your cylinder to slowly bleed down over time.

If was to trouble shoot a leak down situation the first thing I would do would be a replace the o-rings on the manual release valve and then replace the seals in the shuttle valve and see if that does the job. Both of these can be done with average mechanical abilities and require no special tools to accomplish. To tear down the cylinders to replace the o-rings and wipers will require the use of some specials tool that may or may not be commercially available. I know for my Merc I had to make a special spanner wrench to get the end cap off the lift cylinder.

As for storing with the cylinder up or down you might be a bit surprised. With the motor in the full down position you have just as much pressure as you do in the full up position. It’s only when you have the motor in the full upright position with the tilt lock in place do you actually have zero pressure on the hydraulics system.

With this said, it really doesn’t matter to the system. You’re going to wear the seals out on the shuttle valve long before you do any damage from long term pressurization of the system.

[frayedknot]

children playing with the tilt & trim !!! can lock one in the up or down position ! releif valve sticks open sometimes !

keep brat's out of vessell !!!!!!

[WildeOne]

Never used the lock deal ever and never had a problem. I trailered over 10K miles with the same J 140HP and only trimmed the motor up enough for adequate ground clearance ... no more. All lot of trim failures are due to crap internally preventing check valve closure, not any external forces or elements.

Waste of time using the lock deal ever, IMO.
Jim