Pontoon Boat & Deck Boat Forum

...everything I know about it is that it WAS running fine recently but lost reverse gear. It's 90hp. I don't have a clue if it's worth trying to repair by myself but I've worked on cars and motorcycles so not afraid to wrench. I'm told the only way to fix the tranny is to replace in full as Yamaha's require special tools to repair. I'm thinking it is around a 1988 model since that's the year of the toon I'm considering. Thanks!

I have the same era yammy in a 50hp, mind you I only have about 12 hours on it since purchase, but I really like it so far. Starts right up and powers my toon good for what it is!

AaronR wrote:I have the same era yammy in a 50hp, mind you I only have about 12 hours on it since purchase, but I really like it so far. Starts right up and powers my toon good for what it is!

Thanks, I've got a tough decision to make whether to keep this one and put time and money in it or just bite the bullet and buy a new one at 115hp. I guess I was trying to get a handle if this is the kind of motor that can run "forever" (like some of my older BMW motorcycles) or if it's time to cut to the chase. I can't imagine there is all that much difference in performance when pushing a 28 foot tritoon, but certainly fuel economy and smell play into the picture big time.

The biggest trick in working on any lower unit (and that is the transmission) is getting the bearing carrier out.
The special tool is either a slap hammer puller, attached to the propeller shaft threads or a jaw puller that hooks the bearing carrier inside the "through the hub" exhaust port and pushes against the prop shaft.
I ended up cobbling up my own puller of the latter type to get the hub out of my Merc.



On a merc there are 3 loose ball bearings under the bullet shaped cam follower (I am guessing Yammy does it too). Don't lose them.

http://gfretwell.com/ftp/Bearing%20carrier.jpg

BTW before I ripped into it I would be sure there isn't just a linkage problem
Check the oil. It may be full of water.

There is a lot more to a lower unit than getting the carrier out....there are special tools required for the carrier nut, the carrier puller, the pinion nut, the driveshaft puller, the driveshaft spline tool used to remove and torque the pinion nut(how did you do that without the tool?) there is also various different shimming tools required and if you shim it wrong the lifespan is drastically reduced....you'll also need a pressure and vacuum tester to ck for leaks once its all together.
Bottom line -it would be far more cost effective to buy a reman or have it done professionally than it would be to buy all the tools to do it right one time....and you will have a warranty. As far as whether or not it is worth it...that's kinda up to you... i can tell you this..you will not get that money back out of the motor should you ever decide to sell it since you'll probably spend close to what the complete engine is worth just on the lower unit....and there is no guarantee that the powerhead wont go next week....it's not likely as those yammi's were pretty good engines and usually last quite a long time if taken care of properly.....but...that doesn't change the fact that its an old motor.

try this I will be buying one in the next couple of months for my shot Mercury LU.

http://www.sterndrive.cc/mm5/merchant.m ... aLowerUnit


3 year no fault warranty how they do it for so cheap is beyond me, but I won't be complaining.

Over the years I have been in the foot of various motors several times.
I have a lot of those tools and was able to use alternatives for the rest. The only real pain is getting the bearing carrier out. The rest is pretty much like any other transmission job ... without a coffee cup full of loose needle bearings.

On the other hand you can buy a brand new aftermarket foot for about $800 for the most common outboards and you are not buying many Yamaha parts for that kind of money. It comes with a 3 year warranty.

Check out SEI
http://www.sterndrive.cc/mm5/merchant.m ... Code=SE405

Yep SEI,

Ron my link is for your Yammi

Thanks for pointing me to them Greg

A couple of people here have SEIs and they are happy so far.

RonKMiller wrote:I guess I was trying to get a handle if this is the kind of motor that can run "forever" (like some of my older BMW motorcycles) or if it's time to cut to the chase.

I too have 1988 115 hp yamaha that I have been working on. I have talked to quite a few technicians, and they have all said that this era of Yamahas were very solid motors. Things that come to mind from all the different discussions are:

1. the precision bland system is very reliable and ahead of its time compared to some of the other oil injection systems. You should check its operation though before purchasing....let me know if you need the instructions on how to do it.

2. the reed assemblies are solid; none of the techs I talked to said they have never had to replace them.

3. the fuel pumps tend to go out, but the rebuild kits are cheap and its easy to do. Most guys said they replace them every 3 years regardless of performance.

4. the lower units are easily stolen so make sure you have to lock it down when not in use...7 bolts and its out. In fact, we had a rash of yamaha lower units dispear in my area not that long ago.

5. If you are going to buy an aftermarket unit buy directly from SEI. There people on ebay selling them but charge twice the shipping.

If you search around you can find the service manuals on-line, but let me know if you need help locating them.

Good luck

I agree about that late 80s early 90s Yamaha design being bullet proof. I had a 75hp Mariner that is either Yamaha or a licensed copy (I have heard both stories). It was identical to my friend's 90 Yammy side by side with the cover off. He is still running his.
I put over 3000 hours on it and it was still running well when I sold it for the 4 stroke I have now. I never touched anything in the power head, only the screw on parts like plugs, fuel pump etc.
They do like to run tho. When they slapped the slow speed limit on us I had to go to the 4 stroke because I couldn't run it hard enough to make it happy. That is really just a 2 stroke thing.

LTB Racing wrote:There is a lot more to a lower unit than getting the carrier out....there are special tools required for the carrier nut, the carrier puller, the pinion nut, the driveshaft puller, the driveshaft spline tool used to remove and torque the pinion nut(how did you do that without the tool?) there is also various different shimming tools required and if you shim it wrong the lifespan is drastically reduced....you'll also need a pressure and vacuum tester to ck for leaks once its all together.
Bottom line -it would be far more cost effective to buy a reman or have it done professionally than it would be to buy all the tools to do it right one time....and you will have a warranty. As far as whether or not it is worth it...that's kinda up to you... i can tell you this..you will not get that money back out of the motor should you ever decide to sell it since you'll probably spend close to what the complete engine is worth just on the lower unit....and there is no guarantee that the powerhead wont go next week....it's not likely as those yammi's were pretty good engines and usually last quite a long time if taken care of properly.....but...that doesn't change the fact that its an old motor.

Rooster368 wrote:

RonKMiller wrote:I guess I was trying to get a handle if this is the kind of motor that can run "forever" (like some of my older BMW motorcycles) or if it's time to cut to the chase.

I too have 1988 115 hp yamaha that I have been working on. I have talked to quite a few technicians, and they have all said that this era of Yamahas were very solid motors. Things that come to mind from all the different discussions are:

1. the precision bland system is very reliable and ahead of its time compared to some of the other oil injection systems. You should check its operation though before purchasing....let me know if you need the instructions on how to do it.

2. the reed assemblies are solid; none of the techs I talked to said they have never had to replace them.

3. the fuel pumps tend to go out, but the rebuild kits are cheap and its easy to do. Most guys said they replace them every 3 years regardless of performance.

4. the lower units are easily stolen so make sure you have to lock it down when not in use...7 bolts and its out. In fact, we had a rash of yamaha lower units dispear in my area not that long ago.

5. If you are going to buy an aftermarket unit buy directly from SEI. There people on ebay selling them but charge twice the shipping.

If you search around you can find the service manuals on-line, but let me know if you need help locating them.

Good luck

I'm just going to buy a new engine. Although I would love to give restoring this one a try the first time I get stranded in the middle of nowhere I just know I'll regret it. 23 year old pontoons are one thing - but a 23 year old engine...