Calling all Pre-Alpha Mercruiser 120 and 140 owners

[Old Boat Luvr]

Just purchased a 70 Starcraft with a 120hp I/O and since this is my first inboard/outboard I have some questions.

1. Is there a source for downloading the operators manual somewhere for the Mercruiser? I'd really like to know how to service and maintain it.
2. On the dash the tilt/trim switch has 3 buttons. the top one says "Up" the middle says "Up/Out" and the bottom one says "In". Between the top and middle bottons it says "trailer" and between the middle and bottom button it says "trim". What does all this mean? I thought they only went up and down? The only button that works is the "in" button so not sure what to expect. Also are there any suggestions as to how to get the buttons to start working again?

 

[achris]

Re: Calling all Pre-Alpha Mercruiser 120 and 140 owners

Just purchased a 70 Starcraft with a 120hp I/O and since this is my first inboard/outboard I have some questions.

1. Is there a source for downloading the operators manual somewhere for the Mercruiser? I'd really like to know how to service and maintain it.
2. On the dash the tilt/trim switch has 3 buttons. the top one says "Up" the middle says "Up/Out" and the bottom one says "In". Between the top and middle bottons it says "trailer" and between the middle and bottom button it says "trim". What does all this mean? I thought they only went up and down? The only button that works is the "in" button so not sure what to expect. Also are there any suggestions as to how to get the buttons to start working again?

Can't help you on the first..

The trim panel... You've worked out what the IN button does...

The original design of the other 2 is as follows.

The middle button (OUT) will bring the drive up to the top of the TRIM range, which is roughly 30? up. If you want to raise the drive any higher, like for trailering the boat, then you press both the UP button and the OUT button, together....

One common problem with the design of this system is that when the trim limit switch (located on the port side of the gimbal ring) fails, the OUT button no longer works, you need to press both OUT and UP together..... The fix is to replace the limit switch, but that's a real PITA, so most people just put a little jumper wire in the circuit where the limit switch would be and use the OUT to bring the drive all the way up... IF you do that, just be aware that the centre button would then have no limit control, so you could accidentally bring the drive too far up... (I really don't see how anybody could do that, but I'm not stupid either...)

Cheers and welcome to the wonderful world of boating :facepalm:

Oh, and one last thing... Your drive is not a 'Pre-Alpha', it's an 'MC-1'...

Chris....

 

[Part-time]

Re: Calling all Pre-Alpha Mercruiser 120 and 140 owners

Chris pretty much covered it all, as always. Some of the guys on here are a fountain of knowledge.
Chris also has some very good 'how to' videos on you-tube for when it comes time for servicing your outdrive. They really helped me out alot. (BTW, Thanks Chris!)
Like Chris said, the trim limit switch, the one on the port side, is the most likely reason the center "up" button isn't working. I removed the switch on mine yesterday (be carfull taking the two screws out... I had to work them back and forth 'till they freed up). With the switch off, I had my wife hold the center button pressed in while I worked the switch by hand. After a bit of back and forth it started working. Readjusting it was a bit of a PITA but I eventualy got it.
I also did the same for the starboard side switch (for the trim gauge) and got it working as well.

 

[Oshkosh1]

Re: Calling all Pre-Alpha Mercruiser 120 and 140 owners

I had a similar problem.
I have the same setup and after testing I found that the "Up" solenoid was bad.
Start with taking a wire brush ALL(at the panel AND at the trim unit aft) connections and ensure they are tight.

 

[ziggy]

Re: Calling all Pre-Alpha Mercruiser 120 and 140 owners

i'm gonna guess the trim limit switch is on the under side of the top of the gimble ring (both my '72 and '75 mc-1 drive are/were this way). actuated by the bell housing when it's raised and lowered. this switch is nla. so either jump it, or use both middle and top bottom (trailer function) to raise my drive. just use judgement as to how high to raise it.

here's a place ya can look at the service manual. it might be helpful. you'd wanna look at mercruiser #1 s/m.

 

[Old Boat Luvr]

Re: Calling all Pre-Alpha Mercruiser 120 and 140 owners

Thanks guys! Some great info here! Ziggy: your link takes me to a web page that doesn't work (at least on my computer)

 

[achris]

Re: Calling all Pre-Alpha Mercruiser 120 and 140 owners

Thanks guys! Some great info here! Ziggy: your link takes me to a web page that doesn't work (at least on my computer)

Try this one -> https://docs.google.com/open?id=0B1TAvwZ3TjhfZTgyNWM4MjQtOTdhOS00ODEyLTk1OGEtOGIwOGYwNzAwNGEz