How do I lower the lower unit on i/o?

[immykidsdad]

This is my first boat, and I was crazy enough to to buy an old 1976 Glasply with a mercuiser 188 HP that didn't run. I've got the motor problems fixed (I think) and hope to try and start it tonight. I have water to go to the lower unit, but I cannot figure out how to lower it to where it should be to go on the water. How do I lower the lower unit? Does it need to be lowered to start the motor? Thanks, Mike

 

[oldjeep]

Re: How do I lower the lower unit on i/o?

Should just be a thumb switch on the throttle lever. Have a picture of your controls?

 

[BF]

Re: How do I lower the lower unit on i/o?

on that age of mercruiser, you probably have a either a 3 button panel on the dash, or maybe even a couple of toggle switches. There will be a "trim" button/switch and a "trailer" button/switch. If buttons, they may share a common "down" button. Once you lower it all the way down, the "trim" button/switch is used to adjust the trim while under way. If the sensors still work, it will limit the amount that you can lift up the L.U. while under way (to avoid an unsafe level of bow lift). If you want to lift it higher to come into shore, or put on trailer, use the "trailer" to go the rest of the way up. Try and avoid running the engine when it is tilted all the way up. It's hard on the U-joints (even when the LU is shifted into neutral).

If it hasn't been run in a while b/c of the motor problems, you may consider splitting the lower unit to replace the rubber impeller that supplies the cooling water to the engine (like outboards have). Old ones can be brittle and break. It'd be a shame to toast the motor you just fixed. You might want to just pull the lower unit and grease/inspect the U-joints and gimble bearing while you've gone this far. Greasing U-joints requires pulling the LU from the boat, and is supposed to be an annual thing. Seems tough at first, but I can remove/grease/replace mine in under an hour now that I've done it a few times.

Look in the "adults only" of the mercruiser forum for tons of good info that you need.

 

[haulnazz15]

Re: How do I lower the lower unit on i/o?

Should be the "in" button on the 3-button switch panel. It's the bottom button. If you don't hear the trim pump kick on, then you have a wiring/electrical issue, or the pump motor is frozen.

 

[UncleWillie]

Re: How do I lower the lower unit on i/o?

Does it need to be lowered to start the motor? Thanks, Mike

Yes! it needs to be lowered to start the engine.
In the UP position the U-joints are near their limits.
You can start the engine trimmed full UP and will not immediately destroy the U-joints, but don't do it intentionally.
It is very hard on the joints.

Also do not start it without supplying water to the cooling system. You will do damage in 10-15 seconds.

 

[immykidsdad]

Re: How do I lower the lower unit on i/o?

Thanks Oldjeep, BF, haulnazz15 and UncleWillie for your help and ideas! Attached (hopefully) are two pictures of what I believe are the controls to lower the lower unit. From your descriptions, I'd say the three button controller on the dash board is what should make it go up and down. When I push the lowest button, I hear a whirring sound in the back, but I dont think anything is happening. Nothing happens when I push the two upper buttons. Any thoughts? Also, any idea what the small controller to the right, above the throttle might be? It is multi-position and pivots 360 degrees (or nearly so). Thanks again guys! Mike

 

[BF]

Re: How do I lower the lower unit on i/o?

Hi again.... Yes, the 3 button thing is the trim/tilt control panel. The bottom button ("in") lowers the LU. Whirring sound is what should happen as the trim pump works. The LU should be going down as you hold that, normally takes 3 seconds or so for it to go down all the way. One of the two upper buttons (I don't remember which) is used to trim the drive up to a certain point, and then you use the other button to go the rest of the way up when trailering/beaching. From the markings on it, the other thing looks to be a controller for trim tabs.

 

[hivoltg]

Re: How do I lower the lower unit on i/o?

The top button brings it up. Pushing the middle button and top bottom at once (UP UP)will be trailer mode to bring it all the way up.
Same with down. Both the middle and bottom button to bring it down (OUT IN).

Once its down you just use the top or bottom button to adjust your trim underway.

Atleast that's how mine works.

 

[UncleWillie]

Re: How do I lower the lower unit on i/o?

The top button brings it up. Pushing the middle button and top bottom at once (UP UP)will be trailer mode to bring it all the way up. Same with down. Both the middle and bottom button to bring it down (OUT IN). Once its down you just use the top or bottom button to adjust your trim underway. At least that's how mine works.

This! ^^^

Also the other control is for the Trim Tabs.
I can read "Bow UP, Port Up, Stbd Up" on the base for when you pull it back.

When on the water set it to full BOW DOWN when starting to move.
Once on plane, add BOW UP as needed to adjust the ride.
This is NOT a set it and forget it adjustment. The setting changes every time the speed does.

 

[immykidsdad]

Re: How do I lower the lower unit on i/o?

This! ^^^

Also the other control is for the Trim Tabs.
I can read "Bow UP, Port Up, Stbd Up" on the base for when you pull it back.

When on the water set it to full BOW DOWN when starting to move.
Once on plane, add BOW UP as needed to adjust the ride.
This is NOT a set it and forget it adjustment. The setting changes every time the speed does.

Okay, I had a chance to try the buttons as suggested, and determined the whirring sound is coming from a pump on the transom shown in photos 006 and 009. Two lines are connected to the pump. One goes down behind the motor. I cannot see where it goes, but I assume it goes into the transmission and then into the cylinders that actually raise and lower the lower unit? The other line is a clear line that goes to what appears to be another cylinder on the transom to the right of photo 008 as look at the picture (port side of the boat). The line from the pump to the second cylinder is kind of clear, but you cannot see oil moving through it. However, I do not see anywhere to add the 20 weight oil. Anyone know what the names of the main pump and the second pump are? Where do I add the oil?

By the way BF, I think I will take the lower unit off and replace the impeller and grease the u-joints and gimble bearing. Like I said in my initial post, I'm new to boats so I'm going to have to find a service manual before I try that. What is a gimble bearing anyway?

Thanks again guys! We'll get this ol' girl back on the water soon!

 

[hivoltg]

Re: How do I lower the lower unit on i/o?

As far as fluid goes: The corner of your pump that's dropped down with the big screw in it. That's the fill hole.

Open the fill hole with a screw driver and check what fluid is in it. Use a zip tie as a dipstick, it works perfect for that. They don't make 20w oil anymore. 30w works fine, but first make sure of what the previous owner used. Some people replace it with transmission fluid or power steering fluid. If it looks clear but thin its power steering fluid. You can smell the difference also. ATF fluid is easy to tell from the color.

If the pump has fluid in it...you probably have another problem. If its dry...you are going to get to fix a leak somewhere once you fill it up.

That cylinder in the picture attached to your steering arm is...odd. I have never seen that before. It almost looks like a hydraulic buffer (transom saver?). Odd. Both of those pump lines should end up, in the end, down at the outdrive on the cylinders that raise and lower it.

The impeller is easy to change and I recommend you do it every year. The first time you change the impeller also change the upper and lower housing, since you don't know the boats history. Its cheap and easy to do. Same with greasing the u joints. Im guessing you have a prealpha mc-1 outdrive. Show a pic if you can or serial number off the outdrive.

The gimble bearing is the main bearing the drive shaft out the back of the motor rides on. Mine just got changed. It takes some special tools and glueing in a few seals to do it right. Its no fun to do.

Your boats setup is very similar to mine. I just got done replacing those same log style manifolds and risers. Hardest job ever. 35 year old rusted on exhaust bolts. :frusty:

 

[hivoltg]

Re: How do I lower the lower unit on i/o?

Also two tips: Never start the motor unless you have water. It will ruin the impeller in about 5 seconds. Also never start the motor with the drive up. It will mess up the u joints since the drive shaft is always spinning, even in neutral.

 

[immykidsdad]

Re: How do I lower the lower unit on i/o?

As far as fluid goes: The corner of your pump that's dropped down with the big screw in it. That's the fill hole.

Open the fill hole with a screw driver and check what fluid is in it. Use a zip tie as a dipstick, it works perfect for that. They don't make 20w oil anymore. 30w works fine, but first make sure of what the previous owner used. Some people replace it with transmission fluid or power steering fluid. If it looks clear but thin its power steering fluid. You can smell the difference also. ATF fluid is easy to tell from the color.

If the pump has fluid in it...you probably have another problem. If its dry...you are going to get to fix a leak somewhere once you fill it up.

That cylinder in the picture attached to your steering arm is...odd. I have never seen that before. It almost looks like a hydraulic buffer (transom saver?). Odd. Both of those pump lines should end up, in the end, down at the outdrive on the cylinders that raise and lower it.

The impeller is easy to change and I recommend you do it every year. The first time you change the impeller also change the upper and lower housing, since you don't know the boats history. Its cheap and easy to do. Same with greasing the u joints. Im guessing you have a prealpha mc-1 outdrive. Show a pic if you can or serial number off the outdrive.

The gimble bearing is the main bearing the drive shaft out the back of the motor rides on. Mine just got changed. It takes some special tools and glueing in a few seals to do it right. Its no fun to do.

Your boats setup is very similar to mine. I just got done replacing those same log style manifolds and risers. Hardest job ever. 35 year old rusted on exhaust bolts. :frusty:

Thanks Hivoltg,

I worked late every night last week, so didn't have time to work on the boat until yesterday. I tried using a piece of safety wire to check the oil level in the pump. There is something metal preventing the safety wire from going into the hole. I'm hoping it is there to keep dirt out, and there are grooves around the side to let oil seep in. Anyway, I loosened one of the line coming out of the pump and tried it. Brown oil came out (I believe it is 20 or 30 weight oil), it's not tranny fluid anyway. So I tried a line at the hydraulic buffer/transom saver, with the same result. Same at the two trim cylinders. I then disconnected trim cylinders, and they are stuck solid. I've talked to a local marine mechanic, and he has a couple rebuilt ones I can pick up later this week (will be working late again this week). I'll let you know if that is all that is wrong. Thanks again!

 

[Fishermark]

Re: How do I lower the lower unit on i/o?

That cylinder in the picture attached to your steering arm is...odd. I have never seen that before. It almost looks like a hydraulic buffer (transom saver?). Odd. Both of those pump lines should end up, in the end, down at the outdrive on the cylinders that raise and lower it.

That cylinder is a sender for the trim gauge. It was an optional item. Here's a diagram:

 

[Fishermark]

Re: How do I lower the lower unit on i/o?

By the way - I had the same setup.... since you need to replace the trim rams anyway, I would suggest shopping around a replacing the entire pump and trim rams with a more modern setup. Easier to find parts and to repair. May even be cheaper in the long run as well.

 

[immykidsdad]

Re: How do I lower the lower unit on i/o?

By the way - I had the same setup.... since you need to replace the trim rams anyway, I would suggest shopping around a replacing the entire pump and trim rams with a more modern setup. Easier to find parts and to repair. May even be cheaper in the long run as well.

Thanks for the advise and the schematic! I'll look into how much a new pump costs, and go from there. But to be honest, I'm not even sure if the boat runs yet. I picked it up a month ago, and got it to where I'm just about ready to start it. I hate to put more money into just yet, until I know it will start. I love challenges of bring old things back to life. Last was a 1948 John Deere, now a boat. This is a great website, with lots of good advise! Thanks again!

 

[hivoltg]

Re: How do I lower the lower unit on i/o?

As an option, you can unbolt the trim rams from the outdrive, and let the drive down by hand. See if she starts before you move forward with spending money.

 

[pevaguy]

Re: How do I lower the lower unit on i/o?

I think you are trying to check the fluid level at the wrong place. "There is something metal preventing the safety wire from going into the hole." There is another screw about 1/2" to the right and about 1/2" lower down than the one I think you were checking. That is the fill point.