Have you ever been trying to dock your boat or pull it off the trailer just to turn around and watch your outboard pop up out of the water in reverse?
Why an outboard kicks up in reverse? Outboards have reverse locks built into the trim systems to keep them locked down in reverse. There is either air, debris, or an issue with the trim system allowing the prop to pull the outboard out of the water when in reverse.
Here are the most possible causes for an issue with the reverse locks and what to look for if your engine kicks up when in reverse!
Why does my outboard pop up in reverse? The different scenarios!
There are a couple of different situations that you can find yourself in when an outboard will pop out of the water.
What is happening is when the engine is shifted into reverse. The thrust of the prop is pulling the outboard back out of the water.
The issue is going to be with the trim system which is what locks the engine down when in reverse.
This can be really frustrating when you are trying to reverse into a boat slip at the dock.
Or when you are trying to pull the boat back off of the trailer.
Even when you are trying to slow the boat down or pull back out of a slip or turn the boat around at the end of a canal.
Any of these situations require you to be able to use the reverse function of the outboard.
And if it just kicks up out of the water when you put it in reverse. It’s hard to make these maneuvers.
So let’s look at what exactly is going on here.
What keeps an outboard locked in place when in reverse?
For the most part, most outboards are held down in place when the engine is in reverse. By using the trim system to lock it into place.
There are parts of the system that have essentially check valves that will only let fluid flow in one direction.
So when we go into reverse, these check valves keep fluid from going through specific passages in the unit.
Keeping the engine from popping up out of the water!
What is happening is that either of these check valves is stuck open. Or maybe there is some debris in the passage.
Or even some air in the system that is allowing these check valves to simply not function.
Now, this might get you thinking that this would be an easy repair.
But there are some cases and in many cases. Where it is just a time thing. Where the valves and passages in the unit have just simply worn out.
This means that if you want to repair these systems. Then you are going to need to completely replace the entire trim unit assembly.
And these units can get into the thousands of dollars. Making this a pickle to be in.
But then there are also some tricks that you can try in order to try and fix this issue on a little better budget than just replacing the entire trim system.
Johnson, Mercury, Yamaha Trim And Tilt Systems.
When talking about trim units and the reverse lock function of these units. We are generally talking about outboards that are above say 30-40 horsepower.
Most smaller engines, 5 hp, 9.9, 15 hp will have manual trim systems that are not hydraulic.
These systems will have a mechanical lockout on them that will hold the engine down when in reverse if they even have a reverse gear position on the engine.
But if you are having this issue on one of these little engines. Then you will want to look at the mechanical mechanism that locks the engine in place to make sure it’s not broken.
Now the first thing to look at when it comes to the hydraulic systems though. Is going to be that the unit is actually full of fluid and that there are no leaks.
(You can read this article here to learn more about what exactly a trim and tilt system on an outboard is!)
Many times you will find the outboard kicking up is just a symptom of another issue. Being that the trim ram seals or some other seal on the unit are leaking.
Allowing the unit to run low on fluid or fill up with water. Which makes those check valves not work properly. Here is a video of us fixing a trim unit assembly!
As well as another video showing exactly the functionality and insides of a couple of trim units!
So if you find that you have a trim leak on the system.
Then you will want to fix that leak first, depending on how bad it is.
If you have to pull the unit off, you can just disassemble it at the same time and clean it out internally.
This will get any debris out of the unit, in case that is what is causing the issue.
Cleaning the unit, fixing the leak, and refilling the unit with clean fluid, is usually the fix to this problem.
But if it doesn’t fix it, then one other trick that you can try is to trim the engine all the way up.
Place the lock-out pins in place to lock the outboard up. And then take the fill cap off the trim unit.
Once that is off, take an air compressor and some air pressure, like 80 psi or so. And using a rubber-tipped air nozzle.
You can put a couple of blasts of compressed air into the trim unit. Then slowly take the air nozzle off, it will probably spit some fluid out at you.
But this will sometimes force those check valves open and closed if they are sticky and stuck.
This is a quick little trick that can sometimes free them up and get the unit to work properly again!
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We hope that this has helped you understand exactly why your outboard is kicking up in reverse.
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