Understanding Tilt and Trim

Hi everyone, I'm a newbie to boats/motors, and have been trying to understand tilt/trim on a boat. More specifically, my in-law has a Mercruiser Alpha 1 I/O on his boat (he just got the boat recently). The throttle control has tilt (up/down) on the right side of the handle and trim (up/down) on the left side of the handle. I researched online, and saw explanations of tilt/trim but those showed the tilt having a separate pneumatic operator from the trim. I was just curious but could the tilt/trim on this system have the same pneumatic operators and the difference between tilt and trim is that the trim button is wired to limit switches to limit how far up the lower unit will move whereas the tilt button isn't limited to be able to bring the motor up for trailering? If you press the trim down button, you hear the hydraulic noise like something was being lifted or lowered. If you press the trim up button, you hear nothing, not even a click. This lead me to a few different conclusions: 1) something is wrong with the trim wiring 2) Trim down wiring is wired to tilt down wiring and Trim up is not wired at all. Technically, can you trim the boat using the tilt, seeing that they use the same pneumatic operators? Anyone have a Mercruiser Alpha 1 I/O and care to share how the tilt and trim on their's operate? Thanks for enlightening me.

I don't know if the I/O boats are the same as my outboard, but I had a problem where my motor would trim down but not up. There are two relays, one for each direction on the side of the motor. I was able to pull both of those relays out, tap them on the side of the boat and put them back in and it fixed the problem. A somewhat related story related to tilt/trim. When I first got my boat 7 years ago, I had never driven a boat or ever been in a boat with a motor. I had read up on it and was aware of how to trim the motor up when on plane to get the boat riding on the pad. And I knew that the motor should be all the way down when starting out to get the boat on plane. The very first time I took the boat out, against my better judgement, I let my two nephews come out with me because my sister in law said they really wanted to come along. So, I idle out into the lake and trimmed the motor down. I thought I had trimmed all the way down, but didn't realize the little "clunk" I heard was actually the end of the tilt and the start of the trim range. So, when I hit the throttle, the bow of the boat went way up in the air. My two nephews immediately started crying and said they wanted to go back and told me to stop "doing wheelies". They were about 4 and 5 years old at the time. It wasn't until they were about 10 and 11 years old that I was able to convince them to come on the boat with me. Second time out, it was just my wife and myself and I was more aware of what I was doing and it went much smoother. :-)

Thanks Sslayer. I wasn't thinking when I said pneumatic (air operated) vs hydraulic (liquid operated). So the trim button my in-law has should be working (which the trim up button doesn't). Last time we took the boat out (first time) he used the tilt to trim the boat. I will have to let him know and maybe help him trouble shoot the trim buttons to see why the one is not working.

that's cool fishcrav ... if nothing else, I learned a little more about the mechanics and wiring sslayer looks like he's got it all my boats have only 1 button/control for tilt n trim ... what I do know is that it behaves just like sslayer's diagram... it is slow moving at the bottom of the end of the and another speed kicks in, once it's past the trim limit...

First point about boats and Power Tilt and Trim is everything is hydraulic not pnuematic. The piston cylinders on the Alpha 1 outdrive are powered by hydraulic fluid which is pumped by the hydraulic pump mounted next to the engine in the engine compartment. The Power Trim works by pushing the Tilt/Trim button when the motor is running. Limit switches control the trim range. The trim function has a small range when compared to the overall Tilt of the motor and is used to make the boat bow angle higher once the boat is moving at speed and hence there is less hull surface drag and the boat goes faster. The boat's steering can be affected if the trim is to great of angle. Power Tilt works by pushing the Tilt/Trim button when the motor is turned off. The motor can be fully Tilted (Raised) for loading or other functions. See attached diagram. Good Luck SS

Thanks nihsif. I saw those videos and links before too. What I am still wondering is, as shown in the video, the motor tilts using the two pneumatic arms. The question is, is the trim using those two pneumatic arms too? I don't see anything else to trim the boat besides those arms. So the tilt and trim are basically one and the same. The only thing I can think of is that the trim is the same as the tilt but the trim is limited by the trim limit switch so that when you use the trim button you should not be able to lift the motor up as high as when you use the tilt button. Or there really is no trim and you have to trim using the tilt button. If it is the case that the trim button should work, then something is wrong with the trim up wiring since there is no sound when pressing trim up but there is hydraulic sound when pressing trim down. The tilt up/down button works fine. Again, anyone else have this type of motor and use both tilt and trim buttons? How does the tilt and trim differ in mechanics? Thanks!

did a little research and found a couple things that may help determine the problem this is the stern drive trouble shooting/service manual.. see page 14 for what appears to be one thing you mentioned http://www.boatfix.com/merc/Servmanl/6/6C1R3.PDF this is the manual for the alpha and bravo power trim http://www.boatfix.com/merc/Techbk/97/97hs6.pdf found a youtube that shows the unit being worked on, and might be useful for trouble shooting, and getting to know how it all goes together https://www.youtube.com/watch?v=WebJGxOmBLI