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Ask Dominick Your Own Question
Dominick, Marine Mechanic
Category: Boat
Satisfied Customers: 1009
Experience:  25 Years Experience as Mechanic, 20 Yrs Boat Yard Owner/Mechanic, Factory Certified
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Ihave a9.9 johnson out board that leaks oil out of lower gear

Customer Question

ihave a9.9 johnson out board that leaks oil out of lower gear case but does not water into gear case. i pressure and vacumed tested negative thering on the prop is missing.couldthis be my problem?
Submitted: 2 years ago.
Category: Boat
Expert:  Jason replied 2 years ago.
Hello my name is ***** ***** am I speaking with?
How much pressure did you pump up the lower unit to, and low long did you let it sit for?
Expert:  Jason replied 2 years ago.
Also... Do you happen to have the actual model number on the engine?
Customer: replied 2 years ago.
Hi my name is ***** ***** pumped it up to 35 ip and left over night it lost about two pounds in12 hours and the same with vacum at 25 it dropped about 2 in12 hours. i will be back in 5 with model number. 10r77a serial c29287
Customer: replied 2 years ago.
I could phone if you give the phone number thanks Norm
Expert:  Jason replied 2 years ago.
Hey Norm,
What scale are you using? It can't be PSI as an oil seal would blow out in the low 20's. When you say you pumped it up to 35 ip, what do you mean by "ip"?
Customer: replied 2 years ago.
about 25 psi and 35psi
Expert:  Jason replied 2 years ago.
I don't think your pressure gauge is going to be accurate. When pressure testing, the drives get pumped up to 12 to 15 psi. The seals tend to blow out in the 20 to 22 PSI range. I've never seen an oil seal hold more than 25 psi personally. So I don't think your gauge is accurate.
That being said, if you are loosing gear lube chance are it is the propeller shaft seals. The propeller shaft spins roughly 1/2 of engine speed. So if engine speed is 5k rpms, prop shaft shaft speed is 2500 rpms. In most cases when oil is leaking but there is no evidence, or water intrustion, the propeller shafts are dripping at high rpms, but not leaking then you pressure test the lower unit. Does that all make sense?
Customer: replied 2 years ago.
please give me your phone number Jason so i can talk to you thanks Norm
Expert:  Jason replied 2 years ago.
Hi Norm, the website does charge extra for phone calls. If that is something you want to do I can set it up. But there usually isn't anything that I can't answer over the internet. What kinds of additional questions did you have?

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