OMC outdrive issues

[endneu913]

The most curious symptoms are rearing their ugly head on my new 68 Johnson Reveler. Its the Buick v6 155 hp, with the OMC drive. In a nutshell, the impeller is not pumping water up into the engine. The water is not even making it to the pivot caps. NOW the interesting part is, if i have the lower part of the drive off, and the lower water pump housing exposed, and i put a bucket of water up to it, It sucks the water right up and spits it out an open pivot cap, BUT if its fully assembled and in a very large test tank- it will not suck up any water. The pick up tube is totally clear, as is all channels and water passages. I can even force water up the pick up tube and it will come out the pivot cap, but it wont suck it up! My thought is that there's a gap of air between the bottom of the water housing where the thrust seal ring sits.

Does anyone have a very detailed exploded diagram to let me know what seals or parts must be missing?

Any help at all would be great!

- Grae

Oh if its any consequence, it over heated yesterday and blew apart the wet exhaust elbows on both sides, so its running very hot and getting zero water to the engine.

 

[Howard Sterndrive]

Re: OMC outdrive issues

sounds like the impeller is working, maybe you just didn't submerger the drive far enough intially with the lower unit on.
When the boat is in the lake, the entire drive is under water. That's the conditions it's designed to start in initially. Then on plane. water pressure is hydrodynamically "supercharging" the impeller
Thing is, it's practically impossible to submerge the drive far enough with the lower on. That's why OMC sold a flush adapter for the electric shift drives.

If you dont want to get that adapter, you can use something like this in the hose running up to your thermostat hsg:

sounds like a day late and a dollar short though

 

[endneu913]

Re: OMC outdrive issues

Thanks for that info! With that flush adapter on thought- wouldn't it be making it appear that the impeller is doing its job when it might not really be doing so? Im assuming you would attach a hose to the flush adapter and then be forcing water into the engine, great on the lawn, but not so much in the lake.

 

[Howard Sterndrive]

Re: OMC outdrive issues

With that flush adapter on thought- wouldn't it be making it appear that the impeller is doing its job when it might not really be doing so?

correct. I wasn't suggesting you use it to diagnose the impeller.

to diagnose the impeller, dump boat in lake, start engine with hose off to thermo hsg. and watch how much water comes out.

it should look like a garden hose on half

that's where that prestone flush tee is handy, you just whizz the cap off any time you want to see the flow

 

[endneu913]

Re: OMC outdrive issues

Oh i understand now, thanks!

Looks like i might be missing a few seals, which i picked up at the local shop today. Not sure where they fit into the system, but if helps, they are #42 and x2 #43 in the lower gear case group ( 68 stern drive, lower gear case group. Take a peek if anyone has any help on exactly how they mount up. Thanks!

http://shop2.evinrude.com/ext/index.aspx?s1=8d6b00adc42fc5e76ec376505c0baff6

 

[endneu913]

Re: OMC outdrive issues

Well, the larger of the 3 seals sits at the top of the swivel bearing assembly. The rest of them dont appear to have a home at all. BUT i installed the new 310649 ( larger seal ) and that was the fix! That and fully submerging the outdrive and re-assembling the rest of the lower unit, to separate the water pick up and the raw exhaust air coming out. I have a suspicion that this was some of the entire cause all along, but i never thought about it.

Thanks for everyones input! The Johnson 16 came to life this morning on Lake Tapps, and easily gets to 35mph. Very fun boat!

It does idle kind of low ( listening by ear ) Would the best way to adjust the idle be vie the throttle cable, or at the carb?

Thanks!

- Grae