Rebuild or Scrap 90 Hp M90a Two Stroke

[Graham Anderson]

I was wondering if anyone had any thoughts on this situation. I have an 18 boat with a Nissan 90Plus which is a Tohatsu M90a I believe. It has just had a major failure of which I don't know the exact details yet until the shop gets it apart, but safe to say it is time to rebuild or part it out. I really want to keep this motor or change to a Yamaha 90 two stroke which I have found a new in crate and a next to new with 64 hours on it. Either way I would like to stick with the two stroke because of the weight, and I am getting somewhere between 4 and 4.5 mpg.
If I get the Nissan rebuilt I would rather spend the extra money and get everything done that I need to for the piece of mind, or maybe I will just end up with an old rebuilt motor.
I guess a guy should get the gear case done as well.
Any thoughts on this one would be appreciated.
Thanks
Graham

 

[Sea Rider]

You bought that OB new or it's a second hand one ? was well maintained, flushed after use ? Assume is the latest model of the 90 line, are spare parts available ? A used OB is no indication it won't perform well in years to come, will depend entirely on what was mentioned previously. If the repair cost is not a big deal, repair it, it's a good OB. What's the cost of the Yam being offered ?

Happy Boating

 

[tommarvin]

If you are not going to tear apart and rebuild your tohatsu, then I would buy a yam four stroke with EFI.

If the yam four stroke is to much money get the yam two stroke, don't think about the weight. it doesn't matter.

When I was at fisherman's terminal walking around in Seattle, I did an outboard count, true story ask my wife, there was only one cowling out of about 30 plus outboards
Fishermen only buy yams, I never saw not one other cowling, Yams are the finest outboards on earth, that's why they cost just a little more.

 

[flyingscott]

It depends on whats wrong with the tohatsu If you have a middle crank bearing out you are SOL. The crank is pressed together and the bearings aren't available. The crank assembly is $1600 by itself. Now if the crank is good everything is available to rebuild it. But if you want to rebuild everything buying the 2 stroke yamaha is the way to go. The 90 yamaha is a fantastic motor. The tohatsu/nissan are considered every bit as good and reliable as yamaha without the price they are also good enought to build everybody else s motor under 40 hp. I had to scrap mine out because of the middle crank bearing. The last year of the nissan 90 was 2001.

 

[Sea Rider]

Find awkward that you have to buy the whole darn crankshaft, all Tohatsu's crankshafts are pressed, not big deal, a machine shop can tear it appart fast, you can sort heavy duty standard bearings elsewhere, will need to install/drill pins as those are special manufactured for OB use, not a out of this world repair, but not that simple as buying parts from a shelf.

Happy Boating

 

[flyingscott]

I went that route with my tohatsu 90 just not cost effective. Nobody sells a complete rebuild kit for that motor so all parts need to be sourced separately and the gasket kit is no longer made so an NOS one is about $130. Those motors just become cost prohibitive to rebuild. I will give you a cost breakdown on it.

Rebuild kit that I found with standard pistons only and no middle crank bearings $1000
Oversize piston $115 x3
Gasket Kit NLA so it's NOS $130
And you haven't sourced the bearings and had them modified yet
And the crank hasn't been taken apart yet
And your carbs are not rebuilt yet
And your fuel pump has not been rebuilt everything for that is separate.
Not just any machine shop is capable of pulling cranks apart and will they warranty their work when they modify bearings.
The pin will have to be spot welded on as they are a caged ball bearing that doesn't come apart.
So the bottom line is on mine the rebuild came out to over $2000 with me doing the work.

I will also say this tohatsu/nissan does not have the best customer support for their older motors.
You could buy a yamaha 4 strk efi over a two stroke if you want more weight and less power.

 

[Graham Anderson]

Thanks for all the replies guys. They finally got to the motor and it has little or no compression on the middle cylinder, and all the head bolts are froze/seized, so they were going to try and stick a camera in to see how much damage there was on the cylinder walls. The foreman was going to price out a new powerhead.
I also have a line on a couple Yamaha 90 two strokes, one with`15 hours and another with 64. There are going to be $6500-$7000, which is getting close to a new 70 Yamaha 4 stroke which may be a good option at 260 lbs.

 

[Sea Rider]

If all other mechanical parts are working spot on, you ony need to bore cylinder walls to nexy 0.5 mm super size, install new 0.5 mm pistons, cylinder head gasket, take advantage to perform a complete combustion chamber de carbon, clean all water paths, install a new thermo and that's it. Spare parts shouldn't be expensive, don't know about hand labor nor bore costs. But definitely way cheaper than buying a new OB..

Happy Boating

 

[flyingscott]

If you need any spare parts I still have some left over PM me if you need anything depending on where you are. Sounds like sea rider can get cheap parts for a tohatsu keep in touch with him for sure.

 

[Sea Rider]

It's not that I can get cheap parts, usually buy them through our local Tohatsu dealer with a discount and even from US Tohatsu dealers at their list prices. Personally don't like to scrap OB's when the repairing cost is not that huge and the OB is a modern costly one. Parting an OB and selling its parts to buy a second hand one or even a new one is not used here. Luckily have cheap hand labor and machine shop costs that's why like to overhaull OB's. If an OB costs say $ 1,000, what % would you guys be willing to spend to bring back to life that OB and not part it out ?

Happy Boating