9.9 yamaha case corrosion?

[JohnVH]

I just aquired a 9.9 model with a hole in the upper part of the case, is this normal? Anyone else seen this? Runs great, looking for tips on fixing, and figuring out what year it is.

 

[robert graham]

Re: 9.9 yamaha case corrosion?

Looks like some type of impact broke a hole in the case and it was covered/repaired with duct tape. You could replace it, tape it, weld it, lots of ways to deal with it. It all depends on how much it bothers you. I guess an 1/8" aluminum plate could be cut, formed, welded on there, still gonna look like a patch job. A new case would probably cost too much $$$. I've used JB Weld to fill cracks and chips, then file/sand, paint...maybe that's the best way to go, just based on your photos! Good Luck!

 

[JohnVH]

Re: 9.9 yamaha case corrosion?

Yes it was covered in duct tape, after it corroded open. I got it from the origional owner and it has not been hit by anything, somehow water got inside there and it ate its way out. This happen to anyone else?

From research Ive found its an '98 motor, runs like a top, electric start and alternator.

 

[JohnVH]

Re: 9.9 yamaha case corrosion?

Also, anyone know where I can get a manual on how to take this thing apart? Like to take the powerhead off and get into this case to see whats up in there and how to stop water from getting in.

Thank you

 

[sdsaw]

Re: 9.9 yamaha case corrosion?

That crack is from salt crystals that build up around the oil tank and expand to the point of breaking the case from the inside out.
Same thing happened to mine.
It doesn't matter how much you flush it after using it in the saltwater because the flushing never reaches this area.
I believe what causes this is the heat from the oil tank creates a "greenhouse" effect and the saltwater evaporates around the oil tank, leaving salt crystals behind which builds up over time.
I disassembled mine, welded the case from the outside and added a fitting in that area to be able to flush around the oil tank.

I highly recommend getting a factory workshop manual before tearing into it

 

[JohnVH]

Re: 9.9 yamaha case corrosion?

Thank you! I was thinking about a manual also. does it have to fully come apart? Ive tried to find info online about doing it but no luck.

By the way, you have that top plug, where does it drain?

Thanks again!

 

[robert graham]

Re: 9.9 yamaha case corrosion?

If it's in fact a cavity area where salt/sand/corrosion accumulate, then would it be possible to just fill that area with something like body filler/bond-o/JB Weld/other?, eliminating the problem? sdsaw's repair with drain plug looks pretty good, but maybe just a filler would solve problem easier and cheaper? Good Luck!

 

[JohnVH]

Re: 9.9 yamaha case corrosion?

Well, in the center of the case I believe is the oil container for the engine, so you would permanently be joining the engine in there I think.

 

[sdsaw]

Re: 9.9 yamaha case corrosion?

Thank you! I was thinking about a manual also. does it have to fully come apart? Ive tried to find info online about doing it but no luck.

By the way, you have that top plug, where does it drain?

Thanks again!

You can probably just leave the hole without repairing it and it will run fine.
You may see some exhaust escaping through the crack but that area is not essential for proper operation
You can have a welder weld a patch over the crack to hide it without any disassembly. The drawback is that you will still have the salt build up in there

Here's some of the old parts that were replaced prior(4 yrs) to this happening to help you visualize what will be involved. The parts may look different from your since this is a 1988 model

The powerhead(not pictured), base plate and oil tank will lift out as a unit from the mid section case
You will be unplugging some of the electrical plugs, battery cables, fuel line, hoses, throttle and shift linkage

Port view

I'm guessing that you have some salt crystals built up around your tank so it may take some persuasion
to get it apart.
At this point, you can clean the salt off and have a welder patch it up

The top plug is a 3/8" tapered pipe thread brass fitting and a separate plug. I tapped the case for the fitting.
The purpose of it is to be able to squirt freshwater around the oil tank after saltwater use
That water drains down to the exhaust/prop area

Hope this helps
Scott

 

[JohnVH]

Re: 9.9 yamaha case corrosion?

I was looking at the water plumbing on the motor and it purposely throws salt water into the case, must be to cool the oil? No wonder some fail!