OMC 9.9 / 15 impeller housing related questions

[Alan]

Hello to all;

Two questions, related to replacing the impeller in my ’79 OMC 9.9.

Which lower water tube grommet is correct for my longshaft?
I’ve read that they are not interchangeable; the one which was on it is the larger one in the pic. Smaller grommet is the new one.

And, it looks like the impeller cup was glued in. Is that the way it’s s’posed to be done?
I thought it was rust, but peeled part of it off and discarded that theory.

Many thanks, and happy motoring to all;
Alan

[crosbyman]

http://www.marineengine.com/parts/johns … n=Gearcase

parts 37 looks like the one on the left ….

Joining AOMCI has priviledges 🙂

[johnyrude200]

The larger one. It’s to help guide the water tube in when putting the gearcase back on. You can use the smaller one, but it can be hard to get things lined up. You might want to spray a little WD-40 or PB blaster on the rubber grommet orifice to allow the copper tube to settle in more easily. Sometimes they can pierce the rubber if forced in, or worse yet, fold over and actually block water flow through the motor (that’s if the tube is misaligned and gearcase forced on during reassembly).

There shouldn’t be glue in the SS cup in the impeller housing, at least I’ve never seen it before. You just set it in there and re-assemble. If it’s not staying in there for some reason, you can always use a little petroleum jelly to hold it in place temporarily.

[fleetwin]

Unfortunately, you can NOT use the larger grommet on your engine, even though it sure makes installation much easier, you must use the grommet on left (shorter one).
I just happened to prove this to myself last year! The taller grommet, when used on engines with the sealed exhaust megaphone (like yours), seals up the "wall of water" drain. I tried the taller grommet and quickly found out that water was trapped between the exhaust housing and the inner exhaust tube when the engine was tilted up/pulled out of the test tank. This trapped water could find its way back into the powerhead, especially when the engine is removed from a boat and loaded into the trunk of a car/truck bed.
The taller grommet (one on the right), is used only on 9.9/15s with the open exhaust megaphone.

[optsyeagle]

I have always used the smaller grommet on my 1975 and 1976 models and I checked the parts list and OMC recommends the same grommet for my motors as they do for the 1979 model. I always slather grease on the inside of the grommet and the outside of the copper tube to ease the mating during reassembly.

No glue needed on the cup. It isn’t going anywhere and cannot turn inside the housing so I don’t see any value with it. Even on reassembly I never had a problem with the cup to housing. Just hold onto both until it is on top of the impeller that is currently on the driveshaft and plate, and push down on the housing while turning the drive shaft clockwise. Soap up everything (impeller, cup, plate) so that the impeller slides into the cup easily and you should be good to go.

[chris-p]

yeah DONT use the larger grommet. Bad things can and will happen to the powerhead like Don said!

Gluing in the cup is a manufacturer recommendation. I personally don’t, but don’t tell them. 😉 They recommend it though.

[johnyrude200]

Good info to know about the grommet sizes, hadn’t run into that trapped water issue yet…and I won’t in the future now, either!

[Alan]

Can’t thank everyone enough for the info!

I was sure I read somewhere that the grommet choice was important; I’m very glad to get that clear. I suspected the smaller one was correct, ’cause Dan generally gets ’em right.

This motor’s never drained right after use, and always left a puddle of oily goo. Maybe the correct grommet will clear that up.

I’m also surprised to learn that gluing the impeller cups in was / is recommended! First I heard of that.
Pretty sure it’s not going anywhere after it’s all bolted up, so I may skip that step.

Again, many thanks, and happy motoring!
Alan

[Casey Lynn]

Depending on how long the engine is idled, how cold the powerhead is running and how rich the mixture is, etc, the puddle of oily goo is not going to go away because of the grommet.

[PugetSoundBoater]

I have read on Leeroy’s Ramblings website,who has thoroughly researched OMC 9.9/15. I’ve printed out quite a bit of the info for reference on my current motors. He found that you can use the taller conical grommet on a short shaft IF you drill two 1/8" hole on either side of the "water escapement area" ,the loose fit or slotted area where the water tube exits through exaust housing as it heads to the grommet. Hard to explain and depends what style inner exaust housing. would be happy to email you a photo of this MOD I did on my 1976 Evin 9.9 short shaft. Works great and I have no issues ,run for 30+ hours. Also be sure all your drain holes are clear!

"Some people want to know how a watch works, others just want to know what time it is"
Robbie Robertson

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