Need help removing lower lower unit on 79 OMC

[Aaron_M]

Re: Need help removing lower lower unit on 79 OMC

How does the mechanic know the outdrive's impeller doesn't pump water? That outdrive doesn't work with muffs and I see that it hasn't been modified to accept a hose port. Did he dunk it in a tank? Unless the impeller is below water level it won't suck any water at all.

I have two mechanical shift OMCs and one electric shift OMCs. It is not uncommon for a mechanical unit to be replace with an older electric shift unit. The mechanical shift low ends are harder to find and not as strong as the older electric shift models. To replace the impeller is a chore, and you either need a helper you you have to be strong and good enough to wrestle the heavy low end back onto the top end when your done. It took me an hour of bruising my arms and legs to get mine on today when replacing the impeller, and I've done it twice before.

You have to remove the exhaust port/rudder and under that are hiding 2 more bolts. Make sure you leave at least one of the 6 side bolts halfway threaded so the low end doesn't fall when you get all the bolts undone.

You have two options on the wires that will be hanging onto the low end. You can do it the correct way and detach then at the mid drive which means spending 30 minutes fishing back through the mid drive when your done, or you can do it the "other" way and just keep the low end hooked up and in your way.

Next you have to take the top of the out drive off. To do that you remove the the 5 bolts on top and it just falls down. You can then access the pump housing.

You will remove the 4 very large bolts and then the pump and housing will come off with some persuasion.

Then, simple replace the impeller and reassemble the out drive. Make sure you twist the impeller the proper direction. It won't last long if you put it in backwards.

Thanks for that long reply!! I got the outdrive off today. I ended up just marking the wires and cut them. I removed the 5 bolts up top a few days ago and all but 1 broke. Then I removed the 6 bolts attaching the lower drive to the upper and all 6 broke. There is one more bolt right about the water intake but the flat head screw that is holding on the grill is really tight so I'm going to work on that some more tomorrow. The mechanic had tried to connect the muffs to that water input and said it should suck through it but I dont see how thats possible without an air tight grip with the muffs. The water pump may even be good but my guess is that its got to be old since all these bolts were so hard to remove so i might as well replace it. The water pump I ordered comes in today (thursday) so I hope to get it installed. Thanks for the help I am sure I will need more!

 

[rs2k]

Re: Need help removing lower lower unit on 79 OMC

Thanks for that long reply!! I got the outdrive off today. I ended up just marking the wires and cut them. I removed the 5 bolts up top a few days ago and all but 1 broke. Then I removed the 6 bolts attaching the lower drive to the upper and all 6 broke. There is one more bolt right about the water intake but the flat head screw that is holding on the grill is really tight so I'm going to work on that some more tomorrow. The mechanic had tried to connect the muffs to that water input and said it should suck through it but I dont see how thats possible without an air tight grip with the muffs. The water pump may even be good but my guess is that its got to be old since all these bolts were so hard to remove so i might as well replace it. The water pump I ordered comes in today (thursday) so I hope to get it installed. Thanks for the help I am sure I will need more!

I kind of doubt it's the impeller. I'll be shot for saying this, but the OMC stringer impeller is far superior to the mercruiser impeller. It lasts much longer than two years and can easily outlast mercruisers impeller in dry run.

I replace a 5 year old impeller last year last still looked good enough to use.

My experience is that the OMC stringer WILL NOT suck up water. It can only push water. I am having some trouble with my mechanical out shift impellers. The mechanical drive is setup to use muffs, but muffs are just about useless on them. I've got to hold the muffs as hard as I can to get the water level up to the impeller to push water to the engine. Once the impeller is primed I can let go of the muffs, but it only works for about 3 minutes before it looses it's prime.

I just went through the low end of one of these drives today and saw everything is just as it should be. All the seals are in place and it has a good impeller, but it still suffers from the suction problem.

You either need to get an OMC flush adapter kit or a radiator hose flush adapter kit for your drive. That way the water comes in above the impeller.

 

[rs2k]

Re: Need help removing lower lower unit on 79 OMC

I think the stringer drive is a great out drive.

I like them for these reasons:

1.The boats stringers have to be made stronger to use a stringer drive which means you usually get a better quality boat with it.
2.They are ultra simple to winterize... You pretty much do nothing to the out drive other than change the oil and make sure there's no water in the exhaust or intake pickup.
3.The turn radius on a boat equipped with a stringer is incredible.
4.They are bullet proof... if you remember to keep the correct oil in the out drive and make sure it stays in there.
5.The impellers are built tough.
6. The boot is stronger than the bellows on a mercruiser. Stronger means safer IMHO.
7.All the power from the drive is put directly into the stringers. The transom takes no pressure at all which means they hold up longer.


The bad things are as follows:
1.The tilt motors are weak.
2.The trim feature is very odd if you have it.
3.The electric shift uses outdated pin drive props that limits your props available. I always carry a spare prop, pin, and spinner on my electric shift boat just in case the pin decides to break.
4.Parts can sometimes be difficult to find.

 

[gjcombs]

Re: Need help removing lower lower unit on 79 OMC

All,

Great thread here. I have a 1981 OMC 800. Aside from the Seloc and Clymer manuals, the catalog from GLM has been a great quick reference and cross-reference to OEM part numbers.

Attached is an exploded view of what you are dealing with.

Also, you can download the full manual for a week from the date of this post using this link. Or search GLM.

http://senduit.com/f70d8b

Regards,

Jason

 

[Aaron_M]

Re: Need help removing lower lower unit on 79 OMC

Alright, I got some more pictures. My mechanic told me the impeller was in the lower unit just above the propeller... After taking the whole thing apart I could not find it.. Now I just looked at the diagram that gjcombs put up and that looks like its above the lower unit which is still attached to the boat.... So I'm not going back to my mechanic... Since I have this thing apart anyway is there anything I should do to it? I have a few more pictures on page 2..

 

[Aaron_M]

Re: Need help removing lower lower unit on 79 OMC

Few more pictures

 

[gjcombs]

Re: Need help removing lower lower unit on 79 OMC

I would order upper and lower seal kits and replace what you can. They are about $45 a piece.

www.sterndrive.info for bunches of information

 

[rs2k]

Re: Need help removing lower lower unit on 79 OMC

Look up into the mid section of the outdrive. That's the tilting part that's still attached to the back of the boat. You should see 4 huge bolts. Undo those 4 bolts and the impeller and pump housing is in there. I could easily be wrong, but I have a feeling you'll find a good impeller. Even if it looks perfect I would go ahead and replace it anyway since you're this far in.

 

[BLDFW]

Re: Need help removing lower lower unit on 79 OMC

What was the outcome of this?

I had a similar experience with water not consistenly pumping so removed the outdrive and started to dismantle it but started encountering problems with the unknown on my '70 Evinrude Explorer. I "assumed" the V6 and Electric Stringer sterndrive on the boat were original but found both had been replaced at some point.

Given the variety of differing models offered over the years I found it impossible to move forward with any confidence without knowing what stringer I had in my possesion. It took me over a week to finally figure out which outdrive I had and that was only with a suddenly recalled memory from an Evinrude fan on another site.

I could feel my sphincter start to tighten as I read my way through this email thread given my experience thus far. You can't really order any parts with confidence without knowing specifcally which outdrive you have. Granted many parts continued across models but not necessarily between sets of years...ie; 1964-1967, 1968-1972, 1973-1977. I determined that my V6 was a '64 vintage and the outdrive, a '65 vintage, a far cry from what was orginally on the boat. My outdrive is of the vintage hardest to find parts for, especially without OEM part numbers, and later year parts can not be used on it.

At the top of upper unit, under the cover, there is a small "welch plug" (looks like a smooth freeze plug). It may have a logo on it but stamped in it should be a model number (ie; HU-13E, HC-14C, etc). That will identify the year, HP and ratio of your outdrive. From there you can determine how to move forward.

I'm looking at your pics and most of them are of the lower unit. The pump housing is bolted from the bottom up to the upper gear housing. I agree with the others about the impeller. On mine, the impeller was quite sturdy and still pliable but I am replacing it anyway. Given that my pump stopped pumping water, and that I found slight foaming in my fresh oil, I have opted to replace all the seals. It was that decision that lead me to determine that my outdrive and engine were not original. I had to finally order a correct OMC service, parts, and owners manual so I could be sure I ordered the right parts. I just got it today as a matter of fact and found using the OEM part numbers, that I can still get various seals and O-rings though some are non OMC parts. Unfortunately I have to order the parts indivdually as the "kits" you see referenced out there are for 68-73 or higher vintages only.

If you have not already, I encourage you to fully verify what outdrive you have before you start ordering any further parts. I also encourage you to order a correct year OMC service manual even though it might be a tad spendy. It will save you much agravation , time, money, and misery down the line. The manual was ordered through KenCook.com.

 

[rs2k]

Re: Need help removing lower lower unit on 79 OMC

To complicate matters even more is that you can mix and match low ends onto the later model intermediate housings.