312 fastech throttle trim problems
 

What would cause my trim button on my throttle not to work, my trailer buttons work just fine, im assuming its the switch,any other ideas?

it could be the switch or if you have a trim limit switch on the drive that could be the problem also.

would the limit switch affect both drives ? by the way, what is a limit switch?

A limit switch is used to stop the drives from going past a certain point when trimed. This stops the driver from moving the drives to far out and damaging the u-joints in the in put shaft. The only way to go past them is with your trailer switch.
:cool:

So there a limit switch for each drive correct?

Im wondering if one of the diodes are bad going to the throttle trim button, becouse I can use the trialer trim buttons just fine, and if it was the switch it usually only goes bad one way or another (up or down), get the test light out i guess.hopefully there is just an inline fuse bad

I have weirdness in my 2003 292 as well...Sometimes on the first trim up of the day (via throttle switch), only the starboard side drive moves up. I then use the trailer switch to bring the port drive up, and after the the throttle trim works both drives for the rest of the day.

One of those things I can live with for now...

You may try and have a marine mechanic look at your limit switches and clean them. All they are is a reostat type switch and after being in the water may have dirt builtup on the coils. That is why you can trim it w/trailer buttons and not the throttle switches. They are dirty and not making contact until you cycle them one time.
:cool:

P.S Yes there is one for each drive!

If the dash switches work OK, then isn't it more then likely there is a problem with the relay pack, the diodes, or the switch in the handle? Just thinking here, that the limit switches work with either the dash switches or the trim in handle, so I would conclude it is a problem with the circuit between the handle and the switch, not the limit switch.

Am I missing something here?

Hope this helps,
Dave

Edit: Trailer switches work OK...limit switch could be the issue. Is there a limit switch on this application? My 353 does NOT have limit switches!

Dave

So on another note, can the limit switches be removed, or somehow be bypassed, there are times when I have to use the trailer button to get just a little more lift, I wish I didnt have them, well I say that until my wife drives it.

My 'once in a while' trim problem fired up with a vengeance this weekend, the first nice weekend of the year, too.

Now neither the dash trim switch or the throttle trim switch will raise the port-side outdrive. Trailer switch works, though, so at least I wasn't dead for the weekend, but it is frustrating.

Where is the drive limit sensor located? Is it something I can repair\replace, or is it best left to the dealer?

Mine is working great now, I dont know what happened.

Are you still having problems? If so check and make sure your wiring harness is plug in tight on your port trim pump. I think it has 3 wires in a plug one blue,one green, and a black.
:cool:

the trim limit switch is teh black puck on teh left side of each drive. it has a range that allows continuity and a range that does not. this alows you to trim only to the max tim before excessive angles on the u joint.

you can adjust this stop point by loosening the two screws on the limit puck and rotating slightly until you reach the proper max angle.

I adjsuted both of mine to be the best trim for top speed run on a smooth day ( this was less than the max trim specification)
let me just hold both trim buttons without watching he indicator gages. they stopped right where I want them to.

there is a specification by mercruiser for the max dimension from the two bolts on the trim cylinders. make sure you do not exceed this.

the issue can be a bad limit switch, or mis adjusted, or swithc issues as discussed above.

however..... this issue can be an indicator of another issue.
on both of my bravo drives . I found that the pivot bolts behind the pucks had rotated. ( resulting in a mis adjsutment of the limit puck)

sometimes you can just retighten them ( 50 or 90 ft0lbs) check the mercruiser service manual

but. on two of mine the bolt actually stripped out. The solution is a stainless helicoil kit. I have replaced two threads, and loadned out the tap adn isntaller kit to three other OSOers now ( actually someone never sent it back to me.....)

so checc the bolts behind the pucks.
then have someone hold the trim button and slowly rotate the puck to see if it will complete the circuit, then yo ucan fine tune to get the final trim ram extension.


Ramb

Took the limit switch\sensor apart on on the port drive and it had some corrosion on the contacts. Cleaned it up, re-assembled with some dielectric grease, and now works perfectly. Also gave me the chance to teak the adjustment so that both drives now top out at exactly the same level.

30 minutes of work and cost me nuthin' but labor. Thanks for all the advice.