1998 Yamaha 115 V4 2 stroke - Gearbox Removal.

[PhilDig]

Hi,
I have a 1998 115 horse Yamaha V4 Outboard which has developed a crack in the lower gearbox casting, from the side of the prop. A problem which i am led to believe is due to the motor (previous owners) being stored in the tilted up position.

I want to remove the gearbox, so i can strip it & get the casting repaired. I am new to boating but a have a pretty good mecanical background, having spent my life off road biking.

I have removed the six bolts holding the bottom of the leg to the centre section, but i am loath to try to force the casings apart as i dont know if the verical shaft is pinned or how it is located to the top of the motor.

Can anyone help please.

Thanks,

Phil.

 

[robert graham]

Re: 1998 Yamaha 115 V4 2 stroke - Gearbox Removal.

There may be another bolt up under your zinc trim tab fin. Remove black plastic cap from back of motor foot, socket wrench to remove trim tab, then socket wrench up in there to access that bolt. Then you should be able to carefully slide the foot off. Good Luck!

 

[robert graham]

Re: 1998 Yamaha 115 V4 2 stroke - Gearbox Removal.

One other item, if your motor has been used in saltwater then you may have corrosion between the lower bearing carrier and the case causing swelling of the metal and cracking the case. Bearing carrier may be difficult to remove, but if you can get it off, then welding the case may work. Good Luck!

 

[PhilDig]

Re: 1998 Yamaha 115 V4 2 stroke - Gearbox Removal.

Thanks for the info - much appreciated.

Just one more thing. So am i right in thinking the vertical shaft is just splined and should slide out of the motor when i have removed all the bolts from the casings, or is it keyed or pinned to the output shaft from the top of the motor.

Phil.

 

[robert graham]

Re: 1998 Yamaha 115 V4 2 stroke - Gearbox Removal.

The driveshaft is just splined into the powerhead and should slide right down. Be sure to clean the splines and use waterproof grease on them for re-assembly, as there have been some nightmare cases where splines were rusted/corroded into powerhead and wouldn't come down.
If your crack is on a bearing or seal surface then welding may not be an option, but used/rebuilt lower units are available on-line. Good Luck!

 

[PhilDig]

Re: 1998 Yamaha 115 V4 2 stroke - Gearbox Removal.

Thanks Very Much for the info Robert, i really am grateful.

Regarding the welding, i have an engineering toolroom at my disposal, so accurate remachining of welded areas shouldn't be a problem - fingers crossed & thanks again for your help.

Phil.

 

[robert graham]

Re: 1998 Yamaha 115 V4 2 stroke - Gearbox Removal.

Hopefully you may be fine with the welded repair. I have an old motor that I still use that has a welded gear case, although it's only a 3HP. If your crack is caused by corrosion at the bearing carrier, I've heard they could be a real bear to disassemble, but it's worth a shot!...Good Luck!