Lower Unit Making Noise - Water in oil - Replace or Repair or OK?

[thereistand]

I need some input... I purchased a used pontoon boat last week. It is a 16ft with a Johnson 48 hp (1988 model). Took the boat out on the lake. The engine ran great, very smooth. I ran the boat about an hour before I started to hear an unusual sound coming from the engine. The sound was only present while the motor was in gear (a mild consistent clanking or slapping sound). The sound would get worse at higher RPMs. I immediately went back to the boat ramp (about 10-mins away) and trailered the boat. Once back home I pulled the dope plug on the lower unit. A white milky liquid poured out. Yep, water in oil. I called around to a few dealers. I was told (3) different things: 1) "Water in lower unit and making a sound" - "the lower unit is 100% bad". Will have to replace (he wanted to sell me one installed for $1150.00. Another dealer: "water in oil and making a sound could be corrected by changing the dope and replacing the seals" - "sound might go away". Third dealer: "Bring it in, can-not tell you anything without looking at it" (to me the third dealer got it right, I know someone needs to look at the unit before diagnosing). I know I need to take it in somewhere, as I am not a boat mechanic. However can anyone tell me if I need to start looking for a good used lower unit, or can a service and re-seal fix the problem? Would the break down of the dope cause the noise by itself? Or has something broke or worn to the point that changing the dope would not correct?

Thanks for any advise.

 

[wilde1j]

Re: Lower Unit Making Noise - Water in oil - Replace or Repair or OK?

You are perhaps referring to the clutch dog (and fwd gear) being bad? The result is jumping out of gear under load and results in a periodic bang or violent lurch (which may be hard to see/hear on a pontoon boat). Assuming other parts in the lower unit are OK, should be less than $1150 you were quoted for a rebuilt, even with some new seals. The water is caused by leaking seals (can be prop shaft, drive shaft, shift rod and/or vent/fill screws, your choice). Further, it's not an OK condition at all.

It's impossible to know what's needed without some further investigation and perhaps disassembly to nail all parts needed.

BTW, there are no "dopes" in your motor that I know of.

 

[thereistand]

Re: Lower Unit Making Noise - Water in oil - Replace or Repair or OK?

It does not sound like it's the clutch dog, I had an older bass boat last year with that problem - The sound I hear is very "fast" kind-of a fast paced ping or clang noise. It is not jumping in or out of gear, or bumping or anything like that. The sound I hear is just an load as the engine and is constant - does not let up until I take it out of gear and then it goes away. The sound gets louder as I increase RPMs, while in gear. In this boat, the driver sits at the very back of the boat (16ft), next to the motor, so I can hear it very well.

(dope? down here in the south, we put "dope" in our rear-ends (on our cars...)

Thanks for the help.

 

[wilde1j]

Re: Lower Unit Making Noise - Water in oil - Replace or Repair or OK?

Could be anything ... did any significant metal come out with the water? Maybe some gear teeth are broken? Probably needs to be pulled apart to know.

Never heard of "dope" before!

 

[thereistand]

Re: Lower Unit Making Noise - Water in oil - Replace or Repair or OK?

Not sure about any metal. Once the milky stuff started to some out I put the plug back in. I will drain the unit tomorrow and look for metal as you mentioned. Do you think the the sound could have been caused by the gears grinding because of the oil breakdown? I know I will need to re-seal everything and service, I am just hoping I do not need a new lower unit.

Just in case: Anyone out there have a good lower unit that will fit a 1988 Johnson 48 hp? I can post serial numbers later if needed.

Going to bed - will reply to post tomorrow. Thanks for the help so far.