Yamaha 90 gearbox removal

[Matjac]

Hi Guys I have a 90 Yam Two Stroke with the gearbox bolts sheared off any advice on how to drop the gearbox? I have given it a bit off a hammering but don't want to damage anything. Is there a better way some how using the trim and a fixed point on the ground? I take it that it just has the 5 bolts holding it up? Cheers Matt.

[Go fast]

I replaced my friends 1995 90hp yamaha. That had 5 bolts. 2 each side. 1 at the back by the gear linkage rod, 1 at front above prop behind the anode fin
Have to looked there?

[Matjac]

Thanks for the reply have just had another look and there are 2 X 14mm bolts on each side two of these the heads sheared off! and two are loose but wont come out then the other 1 X 12mm bolt that comes out from the top has also sheared off, but can not see any other bolts near the gear rod end? the only other bolt is the one that holds the Anode on and that is out and Anode is off. I think the only way is to remove the Power head and bash it from the top any Ideas ????? Cheers Matt

[Flyer]

Hi, if I recollect correctly there area total of 6 bolts retaining the gearcase. 2 each side of the casing, (14mm af). One 12mm af retaining the trim tab/anode and one 12mm or 14mm af in the forward void above the trim anode going up into the exhaust leg. If all 6 bolts are free, it is possible three more problems have evolved. One, the gearshifter spline coupling has seized not allowing the box to drop. Two, the copper water cooling feed pipe in the top of the water pump plastic case has seized or salted up preventing the box to drop. Three, (worst), the spline drive at the top of the gearbox input shaft has seized into the female drive in the lower end of the crankshaft. If the third option has occured, it will be as difficult to remove the powerhead as it is to remove the gearcase. Hope this helps and good luck.

[Woody]

Originally Posted by Matjac

Thanks for the reply have just had another look and there are 2 X 14mm bolts on each side two of these the heads sheared off! and two are loose but wont come out then the other 1 X 12mm bolt that comes out from the top has also sheared off, but can not see any other bolts near the gear rod end? the only other bolt is the one that holds the Anode on and that is out and Anode is off. I think the only way is to remove the Power head and bash it from the top any Ideas ????? Cheers Matt

I would not hit it from the top as there is a good chance you will crack the housing.

Attached is a link to an exploded diagram of the 85/90 gear housing http://www.iboats.com/Yamaha-85-90-h...view_id.272943

Hope this helps

[willwood6]

Don't start hitting it. Yam 90's casting are strong but not that strong.

2 bolts either side, 10mm fine thread with 14mm heads.
1 Bolt holding anode on, get to it from top to bottom of mid section 'tail'.
1 bolt from bottom to top, behind the anode, goes up into midsection.

Sounds exactly like salt corrosion you have. Obviously not been off in a very long time! Bolts get salt build up around them and effectively weld the bolts too the aluminium.
If all those bolts are out or broken then I would suggest applying some penetrating oil or any kind of lub you can find around all the bolt holes and between the mid & gearbox. Leave it for a couple of days then get the heat on it.
Heat gun not enough, will need oxy/acetelyne.
Try to lever the gearbox from the midsection rather than hammering anything. If you can't get a lever in then try a rubber mallet on the fin plate and on the bullet in a downward motion. Be careful!

Good luck with it.
Will

[Matjac]

Thanks for all the help gearbox is now off, a couple tins of WD40 and a fair bit of bashing! Any one out there know how high to run / fit the motor? just for fun not that bothered about skiing. I had a Phanton 90 Yam years ago can't remember how high we ran it then for racing that was over 25 Years ago!!!!

Cheers Matt