Question about Lower Unit

[Mendelivium]

I just bought a rebuilt lower unit for my Johnson 150 XP motor. I have never worked on boat motors much but I got the old one off and the new one on. While doing so, I saw that the rubber seals for the exhaust tube were looking pretty bad but I put them back any way. When I ran the motor with the rabbit ears, I noticed water coming out from that area (exhaust tube area) where the lower unit meets the rest of the motor. Do I need to worry here? I am trying to understand the where water goes in the lower unit in general. Water must come up through the exhaust - right ? Does water normally surrond the water pump housing and shift rod housing ? In other words, where all is the water in the lower unit normally? Are the seals for the exhaust tube there to keep water out or the exhaust in ? If water is leaking from the exhaust tube, there will definitely be water around the water pump housing, etc. Is that normal ? Ok ? Thanks for your input and hope you all had a great Thanksgiving !

Oh also, is there normally any kind of seal between the upper motor and Lower unit ? I saw none on my old lower unit.

 

[wilde1j]

Re: Question about Lower Unit

To your last question first, no the parting line between midsection and lower unit is not sealed. The water pump normally operates under water. The exhaust seal should be replaced.

 

[R.Johnson]

Re: Question about Lower Unit

Your engine has what is called a wet sleeve, or in other word's there is water held in the exhaust housing. This has a cooling effect, but also a silenceing effect. The leakage you see is normal.

 

[Mendelivium]

Re: Question about Lower Unit

Ok so to me it sounds like I am ok ? From your answers, water is normally over the top of the water pump and shift rod. I guess that is where "their" seals come in to prevent water getting down into the lower unit gear area itself ? So the seal for the exhaust is to keep exhaust going out only I suppose ? First poster, you said I should replace the seals. Will I be ok to wait until I replace the water pump impeller in the future ? What will be the effect of waiting ? I don't won't to hurt anything. So I guess I am trying to just say, should I be ok for now then ?

 

[emdsapmgr]

Re: Question about Lower Unit

I'd recommend replacing the lower rubber exhaust 320961 oring sooner rather than later. Since that oring has deteriorated, hot exhaust can leak into the area around the composite water pump impeller housing instead of getting directed out the prop. That heat can deteriorate/deform that impeller housing over time-possibly shortening the life of your impeller.

 

[Mendelivium]

Re: Question about Lower Unit

Thank you all for your input. I really appreciate it.

 

[Chris1956]

Re: Question about Lower Unit

If you look at the mating surfaces of the midsection and gearcase, you may see slots where it is intended that water can exit the midsection. My '98 Johnny 150HP Oceanrunner has these.