OMC 800 sealing the upper unit

[studdy05]

I have completely replaced the upper and lower units aluminum hulls that were rotting on an 84 stringer and tried to carefully reseal things back as I went. The impeller was trash...the upper had been sitting in water with little oil as it rusted out, but the gears looked good and the seals and bearings were not that hard to replace. After about 3 water tests, it seems at WOT it would run hot, but getting back down to 2000 RPMs would cool it off.

After rerouting a power steering cooler to a seperate radiator to increase the water flow directly to the engine from the sea water pump, I think I actually saw some improvement. While testing this out, skipping along at WOT for a half mile or so, my sterndrive lost power, no forward or reverse, and my engine temp headed to redline. I shut it down quickly, no harm no foul to the engine, but after reading/researching threads here and doing some checking, looks like the water pump drive shaft probably gave way.

Two questions: First, reading everything I could get my hands on, I still don't feel like I got a good seal on that impeller - it was the whole shebang kit and I will get another one just in case I need to replace something - but what is the trick to getting a good seal. The manuals seem a touch vague. Links appreciated if this has been beaten to death before. (I am seriously considering a 12v sea water pump mod. in the engine room to assist the OMC design)

Second, if I replace the water pump drive shaft because I stripped it, should I go ahead and order the upper pinion shaft that it connects to? I am seeing tons of people with stripped water shafts, but no comments about what that shaft slides in to...other than grease the fire out of it. Does the pinion shaft hold up better and the weak link is always the water shaft? (Generally speaking here.)

I have been stranded roughly 80% of the time I hit the water with this OMC drive and that is getting old. I don't mind spending the money, or the time fixing it, but I am about to run out of lakes to test on...friendly on goes so far...lol!

 

[chiefalen]

Re: OMC 800 sealing the upper unit

You have a manual? What kind?

Ok water pump shaft as you know goes into the upper pinion shaft. When you had it apart did you look at the splines before you put it together.

You posted lake in your post, this boat was always fresh water used?

Ok take the key out of the boat and put it in your pocket.

Put the drive all the way down, never ever run this setup with the drive anywhere but fully down and water going to the drive.

Put it in gear.

Go to the prop, can you spin the prop bye hand.

IF yes, look at the ball gears are they moving?

If yes, it's the coupler.

If no it's the water pump shaft.

Ebay has them right now.

And after pulling them, my bet would be you need both, hope not.

Ok you need to ge a good seal on the water pump bye using the blue sillycone #2 i believe, permatex.

On the bolt heads that pass thru the water pump housing, the lip of the water pump housing top half and the outside of the housing all the way around.

When you put back on the lower unit, to the upper there was a plastic washer?

You used it?

And the exhaust seal large round plastic ring on the lower unit top lip?

You shoot grease in the hole that is halfway up the drive front side?

There is a zerk fitting in that hole, you can get to it with the drive all the way up, 5- 6 pumps on a grease gun, important to grease that fitting.

Please post your result after you do the spinning of the prop test.

 

[studdy05]

Re: OMC 800 sealing the upper unit

3rd time on lake testing new upper and lower only to find - Upper unit had no oil in it. Maybe a tablespoon. Double checked my new seals and the ones to the ball joint had been put in back to back, but back to back the wrong way and I think this caused me to lose my oil. (Stupid mistake, my first rebuild job. Live and learn.)

Both gears were totally stripped. Found suitable replacements on Ebay, and have them but they are not brand new.

I had bought drive shafts expecting them to be bad, they were not stripped, but will replace them anyway since I have the new ones.

Have another seal kit, and will redo all the seals and O-rings, AGAIN.

New impeller, AGAIN.

New bearings this time.

PROBLEM: Though I can put this thing together in my sleep, and I have the Clymer and Seloc manuals both, I don't know that I can shim this bugger.

In fact, I am not so sure that my shim job from the last rebuild didn't contribute to the gears getting ground off in five minutes of run time.

What would labor cost - roughly - for a professional to shim it? OMC mechanics are rare, but I think I can locate one.

Should I try to do this myself without all the specialized shimming tools and just get it really dang close and see what happens?

Shimming advice appreciated!!!!!!!!!!!!

 

[meesh]

Re: OMC 800 sealing the upper unit

Without the proper tools, your wasting time, parts, and cash.

 

[chiefalen]

Re: OMC 800 sealing the upper unit

How many shims were in it when you got it?

The play should be less than 1/16th.

Have you ever changed out the t-stat?

Have you had the riser off yet?

Hows the engine mounted water pump look.

With this impeller being so oversized i can't see you not getting a great stream of water to the motor.

Do you know where the tattle tale stream of water is that shoots on the ball gears?

Is there a good stream of water?

Do you have installed around the intermediate ball gear a water deflector?

That water deflector is important if not there, the gears could overheat.

Also if you run the drive any where but straight down those gears will wear out pronto.

And if worn more than say 50 percent will put a undo stress on the bearing on the intermediate ball gear shaft.

Also undo stress on the ball upper drive shaft ball gear/ pinion gear bearings.

You never posted if it was the coupler or the water pump shaft that went, or if you did i must have missed it.

If you need to i can talk to you on the phone just pm me and i can maybe talk you thru the problem.

Good luck and g-d bless.

 

[chiefalen]

Re: OMC 800 sealing the upper unit

I must be missing something?

The water pump shaft and pinion shaft were not stripped?

And you over heated?

And no forward and no reverse?

You know your coupler went.

And the motor has to come out to replace it.

And you will find out if the Ball gear shaft is stripped as well.

You do not on a stringer have to remove the drive to pull the engine.

Heres a link to pulling the engine leave the bell housing or some call the adapter housing in place.

http://forums.iboats.com/showthread.php?t=280334

Heres the one to remove the drive.

http://forums.iboats.com/showthread.php?t=275061&highlight=how+to+remove+ball+gear+shaft

 

[fendersfender]

Re: OMC 800 sealing the upper unit

You need to have the shimming tools for this job....and after a reseal, you need to pressure AND vacuum test the gearcase with no oil to check for leaks......maybe you could find a marine shop to help you with shimming...not too many shops will mess with these anymore...good luck

 

[chiefalen]

Re: OMC 800 sealing the upper unit

A lot of times guys use rubber o-rings on the drain plugs.

Wrong move they should be plastic washers.

And the breather holes also plastic washers.

O-rings get squeezed out and you will get water in the drives.

The water pump is the weak link and of poor design in my own inexpert opinion.

The seals i believe are not strong enough, to contain the pressure of this over sized impeller.

And sealing the mounting bolts and around the outside, and inside lip of the impeller housing with permatex is critical.

Thats why i believe resealing the upper every 4-5 years is imperative.

Lower unit is of better design and does not require a reseal as frequently.

As i stated before in my own inexpert opinion.