Omc 120 Outdrive lower unit removal

[mr.andy]

Hey all, my boat has overheated in idle and I suspect my impeller is the issue.

I was hoping someone could walk me through on all the test I can do to determine that before removal of the lower unit.

So far I have taken the end cap off the pivot cap. I let the boat run at about 2k rpm and I would say a decent amount of water comes out . I then tried a method of taking the hose that leads to the the thermostat and let it run at idle which i have it set right now kind of high around 1000 rpm and barely any water came out I tried to fill a 2 gallon bucket of water up in less than 2 minutes but the pumped kind of stopped. So i shut it off..

I strongly suspect it being a faulty impeller in my eyes even though I have never owned any boat before i feel as if it should definitely be putting more water out . I dont know how much water is truly supposed to flow out though so if someone would be so kind to inform me that would be great!

To remove the lower drive I visually see right now 6 bolts, I remove those bolts,are there any other bolts that are hidden that i need to get to before trying to remove this?


thank you!

Andy

 

[Rinker85]

Andy,

It is pretty easy to remove the outdrive, but you need to get a shop manual and follow the step by step instructions. It will start off by disconnecting the shift cable. What year and model engine do you have?

 

[southkogs]

You're a '69 model electric shift, correct?

First - disconnect your shift wires at the knife connectors port side of the engine toward the back.
Second - pull the pivot caps off
Third - get some help, 'cuz the drive's about to get heavy
Fourth - disconnect the brackets at the pivot points, and gently rotate the drive back on the quadrant gear. The shift wires should come right out the channel they pass through the intermediate by.

Impeller should be changed ever two to three years on those drives, so you're probably due.

You want a manual for sure. That'll give you your water flow specs. You don't really want to check flow on a stringer from the garden hose. The way it works on the trailer, the water is pretty much forced up to flow. You want to check waterflow with the drive submerged at the lake.

 

[mr.andy]

You're a '69 model electric shift, correct?

First - disconnect your shift wires at the knife connectors port side of the engine toward the back.
Second - pull the pivot caps off
Third - get some help, 'cuz the drive's about to get heavy
Fourth - disconnect the brackets at the pivot points, and gently rotate the drive back on the quadrant gear. The shift wires should come right out the channel they pass through the intermediate by.

Impeller should be changed ever two to three years on those drives, so you're probably due.

You want a manual for sure. That'll give you your water flow specs. You don't really want to check flow on a stringer from the garden hose. The way it works on the trailer, the water is pretty much forced up to flow. You want to check waterflow with the drive submerged at the lake.

Yes 69 electric shift, I know how to remove the outdrive and such but more curious on how to separate the lower unit from the upper. I did not check flow from garden hose I used a make shift tank and let it suck water up from there

 

[Scott Danforth]

the problem with a makeshift tank is it isnt deep enough to get water to flood the impeller.

impeller pumps dont draw water, they only push water.

use the factory manual to pull the drive apart.

 

[southkogs]

You're going to need the manual for the impeller replacement. I needed to refer to it nearly every time I did one.

The drive will come apart easily. Remove the top cap. After that, the upper will separate from the lower just by lifting.

 

[kenny nunez]

It is easier to separate the lower by removing the 5 bolts and drop the lower with the upper still mounted. The reason is if you do not have a holding fixture to service the drive it can be a real hassle. The way that I always performed this was to have the drive at the 1/2 way lifted point. Of course you must remove the shift wire first as stated. If this is the original 1969 high profile model this should help.
After the lower is off remove the rear pump cover mount bolt, then with a1/2” 13 x1” install it into the pocket where the long bolt was and tighten it. An Allen head bolt works great for this. That way it is easy to tighten the bolt. This prevents the pinion housing from falling out of the upper gear case and dumping gear oil on your foot. Now remove the pump assembly by removing the 3 remaining bolts as per the manual. The impeller housing will probably need to be driven off with a chisel and hammer. Hopefully none of the 5 cover bolts will break. Down here it was very rare for any of them not to break. You may need a torch to heat the area where the bolts pass through the cover. After all they are only 1/4” 20 and break easy because of granular expansion that occurs between the bolt and the housing.

 

[kenny nunez]

Another source of overheating is the copper pipe that plugs into the rear of the swivel bearing. Over a period of time the rubber grommet will be pinched down to a very small hole. This is where things can get tough. The exhaust housing has to be removed and the shift wire passes through a hole that gets corroded to the point that the cable breaks when trying to remove it. Now the swivel bearing has to come off and hopefully the small bolts will not break, the seals have to be replaced along with the cable and the sealing nut that the cable is pulled through. It appears this boat is a”sweet water” survivor so maybe the above warnings will not be an issue. I was an OMC dealer from 72-03.