69 OMC 120 (part 2) with pics

[OMCboater]

I am sooooo close to getting in the water I can taste it, but looks like it won't be as soon as I thought. This has been a 2 year project so far - complete new floor, stringers, transom, engine mounts on this I/O. rebuilt the tilt and trim motors (they were pretty much seized from water but cleaned up nicely and work fine), got the electrics and fuel hooked up today. The engine starts and runs awesome (all new points, condensor, plugs, wires, etc, etc, etc...) but......

I'm not getting any water up to the manifold - verified by pulling hoses off - inside of hoses and manifold are very dry. I should state I had removed the manifold to verify soundness and all was good with it.

Now please take a look at these pics and let me know if I am doing this right. I can't see how muffs would work on this model so I filled up a pond liner that I haven't got around to installing yet. Can anyone confirm for me that that screen above the prop is the water intake, and also that it is in far enough to pick up water?

The first pic is my setup for running out of the water

Second pic is what I believe to be the water intake

Third pic - looks to me like it's in deep enough......no?

 

[wire2]

Re: 69 OMC 120 (part 2) with pics

The intake is under water but your water pump impeller isn't, it's on the vertical shaft above the prop shaft. You have to get the leg much deeper in or use muffs to apply water pressure.
Did you run it more than a few seconds like that? If yes, plan on a new impeller.

 

[wire2]

Re: 69 OMC 120 (part 2) with pics

Ok, I see what you mean, muffs won't fit. Check on eBay for an OMC stringer flush adapter. I've seen them for ~$25 there.
It replaces one of your trunnion caps, (where the outdrive tilts from) and you connect a hose directly to it.

I made one by drilling a 3/8" hole in one, then tapped it to ? NPT thread and put a pipe to hose barb adapter in. When you're done playing, just cap it.

 

[OMCboater]

Re: 69 OMC 120 (part 2) with pics

Thanks for the infor wire2. I didn't run it for long at all - just primed the carb a bit ( a few times) til the fuel pump got the gas up to the carb. I'd say I didn't actually 'run' it, more like just cranked a lot with occassional firing. Regardless, it did fire and everything seems in order (except for the lack of water pumpage) which has confirmed for me that it is worth continuing to work on.

I now understand why it wasn't pulling up any water - it has to be 'primed' by having the impeller beneath water level.

I read about the adapter for the trunnion caps and had considered making my own - maybe I will proceed. But can you answer this - if the hose is connected at the trunnion cap, under pressure, I assume water will be forced both up into the motor and down the leg, where it will meet the impeller trying to push it up. Intuition tells me this shouldn't be good for the impeller and pump....?
Edit: I should clarify - not trying to reinvent the wheel or dispute the procedure as I understand it is the 'proper' way to run these out of water, just trying to understand the science behind it.

 

[wire2]

Re: 69 OMC 120 (part 2) with pics

Technically, yes, you're pushing city water pressure against the impeller but it can & does flow into the engine as well so the pressure isn't much different than normal operation.

 

[Lyndy]

Re: 69 OMC 120 (part 2) with pics

There should be a hole in the bottom of that rudder big enough for a 1/2" hose. Even under City Water Pressure it is enough to reach the impeller. Although the Trunion Cap Adapter is a great alternative and I have it on my Outdrive the inlet hole in the bottom of the rudder is sufficient for flushing. Unless there was already something wrong with your impeller it should be fine and will do the job with the engine in idle.

 

[Lyndy]

Re: 69 OMC 120 (part 2) with pics

If you plan on replacing the the Impeller Assembly, which you should, be aware that the shaft the impeller is mounted on connects to another shaft going up to the Upper Gearcase. That splined connection has a tendacy of fusing from rust. If it is fused, it is a PITA and will likely require disassembling the Upper to get at it and then reasealing the Upper. We have very similar drives and that is what happened to mine. I had someone do the Surgery for me because it required tools I did not have and I did not want to mess around with a component that would be very expensive to replace if things went wrong.