Cracked Lower Unit Yamaha 90

[jburn25]

I hit an unseen underwater object this morning at full speed and cracked my lower unit at the skeg almost all the way to the cavitation plate on both sides. Prop is fine and the engine still works great. I idled all the way back to the boat launch but could've run wide open.

I'm assuming welding the lower unit isn't an option with a crack this big? also, can I just buy and replace the lower unit housing for pretty cheap since it looks like everything on the inside is in good shape? Where to start looking for a used lower unit like this?

Thanks guys

 

[robert graham]

Re: Cracked Lower Unit Yamaha 90

you can buy used lower units but they're expensive! since it's still running, maybe you can press these 2 sides of the crack back together and get it welded by a good professional welder. there are "cooler" welding methods that may not overheat the entire lower unit to the point that the seals would melt. maybe you should remove all lower unit gears and internal parts before welding, then re-assemble with new lower seal, but you could get the welder's opinion on it first. I've had cracks in lower units welded but never anything like that one! that's a crack! It's worth a try and you could get out for the cost of the welding. Good Luck!

 

[triumphrick]

Re: Cracked Lower Unit Yamaha 90

I hit an unseen underwater object this morning at full speed and cracked my lower unit at the skeg almost all the way to the cavitation plate on both sides. Prop is fine and the engine still works great. I idled all the way back to the boat launch but could've run wide open.

I'm assuming welding the lower unit isn't an option with a crack this big? also, can I just buy and replace the lower unit housing for pretty cheap since it looks like everything on the inside is in good shape? Where to start looking for a used lower unit like this?

Thanks guys

Consider yourself lucky. That seawater doesn't do a very good job of lubricating the gears....that lower unit could have seized and taken out the driveshaft, powerhead, etc. A good marine shop can disassemble it and weld it.

 

[jburn25]

Re: Cracked Lower Unit Yamaha 90

Well I'm not sure that i want to have it welded since it is a 2004 and is such a big crack. I wouldn't have hesitated to have any of my previous motors welded but this is the newest one i've owned and i don't want to risk any problems down the road. Looks like I can get the lower unit case for about 100 bucks new online.

Anyone know how hard it will be to swap all the parts from one lower unit to the other? I think I can figure out how to remove it just fine, but taking all the parts out and putting them in the new unit might be a problem.

 

[rodbolt]

Re: Cracked Lower Unit Yamaha 90

its not hard, does take a few special tools though. check the fwd gear to pinion back lash BEFORE removing the drive shft for reference on reassembly.

 

[jburn25]

Re: Cracked Lower Unit Yamaha 90

Well the lower unit I found on eBay got sold before I could get the funds ready. So, I called my local Yamaha dealer/repair shop and they acted like I was crazy when I asked them if they ever repair lower unit cracks. They said they've never done it, they always replace them...

So, anyone know a good place to find a used casing? The dealership wants 600 bucks just for the casing. I don't know if I should just bring it to a regular welder or not

 

[robert graham]

Re: Cracked Lower Unit Yamaha 90

might just squeeze that crack shut and weld it up tight and it may surprise you how well it may work. I have an older motor now that I had welded up and have had no problems with it. It's just an aluminum casting and all you've got to loose is the cost of the welding. Good luck!

 

[jburn25]

Re: Cracked Lower Unit Yamaha 90

So you think a regular welding shop should be fine?

All I need to do is pull the parts out of the lower unit so they won't be affected by the heat, then bring it to a competent welder, then replace the seals and I should be good to go?

 

[jburn25]

Re: Cracked Lower Unit Yamaha 90

Also, all of the lower unit oil leaked out due to the crack. Is this an indicator that something inside the lower unit is broken? I don't want to have it welded back and then realize that my lower unit is getting proper lubrication.

 

[rodbolt]

Re: Cracked Lower Unit Yamaha 90

the problem is looks like the break goes across where the oring for the bearing carrier seals and the shim for the reverse gear sits.

 

[jburn25]

Re: Cracked Lower Unit Yamaha 90

So you're saying you don't think welding it back will do the trick? Just trying to make up my mind here....

 

[robert graham]

Re: Cracked Lower Unit Yamaha 90

Rodbolt knows a lot more about these motors than I do, and it is one helluva crack. you could weld it up and it might be structurally sound, but then you might have problems sealing the unit up with the o-rings and seals, so your foot oil doesn't leak out. Good Luck!

 

[Home Cookin']

Re: Cracked Lower Unit Yamaha 90

me, I wouldn't risk the top half by welding the lower half. Get a new or used casing, or a used lower unit. And with a new casing and old parts, I'd be worried that parts were damaged/bent and might not work right. Keep in mind, too, that a slight bend, like a bent prop, can cause vibrations that eventually harm the whole motor. Think about why wheel allignment is so important.
I might take a chance with an old motor but go price 2004+ 90's.

BTW you have proved that "a little" water in the gear case doesn't keep it from working!

 

[jburn25]

Re: Cracked Lower Unit Yamaha 90

Well, thanks for the responses...My heads really spinning right now lol. I really lucked up with what I paid for this boat, got it really cheap, but I guess the problem with getting a boat nicer than you could normally afford is that you have to be ready to pay for nice parts too. I really don't want to spend 500 bones on a new one so I guess I'll just give it a couple months and try and find a used casing online. In the meantime I'm going to bring it to a repair shop and get the "guts" taken out and make sure everything is ok.

 

[robert graham]

Re: Cracked Lower Unit Yamaha 90

well it's cracked about as bad as it can be without just knocking the entire foot off. maybe after you get all the gears and bearings out then you can get a better idea if welding it up is a viable option. mean time maybe you can locate a good used one at a decent price. if you end up with a used one you'll have to get somebody to reassemble it for you who knows about those shims and tolerances between the gears. you can't "just stick it back together". I'll be very interested to know how you come out on this, so please post your results for us guys to read. Good Luck!

 

[jburn25]

Re: Cracked Lower Unit Yamaha 90

Thanks, I'll definitely let everyone know how it turns out. E-mailed my picture to a local mechanic who was interested in helping me work on it and he said it definitely can't be welded because of where the crack crosses. He e-mailed it to a few buddies as well who had never seen anything like that, they feel it must have been some defect in the cast of the original casing for it to crack like that and not bend anything or other wise affect the lower unit. Too bad Yamaha won't just feel pitty on me and give me a new one haha.

 

[jburn25]

Re: Cracked Lower Unit Yamaha 90

Well I was hoping to be able to update on this situation by now, but I still haven't been able to find a lower unit housing (at all). No new ones, no used ones, nothing. I've found one good deal on a complete lower unit for 500 bucks, I think its about ten years old and pretty scratched up. It's about 6 hours from here, but I may be driving within four hours of its location in about a month so I may see if the guy will meet me half way.

 

[bottomfishin]

Re: Cracked Lower Unit Yamaha 90

I am a certified welder (25 years) and machinist and to repair that back to spec would be very hard. If it is cracked were the O-ring rides I wouldn't try it at all. What you can try is to clamp the halves back together and if it goes back perfect, while it is clamped grind out a section on each side and tack weld really good. Check to see if the carrier goes back in and then grind out and weld a few sections at a time. you may have to go back and grind or bore out any burn-thru though, it would be a difficult thing, personally I would get a case.
Maybe you could help me...I need the dimension from the back of the unit to the shoulder were the carrier thrust washer sits as I had to rebore mine because the gear peices tore off the shoulder. Or better still measured from the front of the unit were the forward gear sits (there is a shoulder there that starts an angle to the bearing bore, in thousands of an inch if you got a caliper.
Thanks

 

[triumphrick]

Re: Cracked Lower Unit Yamaha 90

One more shot at this..these people have had some good feedback, just don't know if they have that unit yet. Can't hurt to try them..

http://www.sterndrive.cc/

Also, this ad..

http://tampa.craigslist.org/pnl/boa/1329117322.html

 

[jburn25]

Re: Cracked Lower Unit Yamaha 90

Thanks for your replies. Judging from your post bottomfishin, I definitely don't think I want to have it welded anymore. The guys here in Shreveport say they can "probably" weld something like that, but i don't think they have the precision that you are referring to.

I would love to help you out and measure that unit for you, but I don't have a caliper. If general measurements will do, just let me know.

Triumphrick, I'll check out that ad for the used parts, thanks alot.