M90A carb question

Hey guys,

Have a 90hp tohatsu 2 stroke. I pulled the boat last summer and it has been in the garage drying out. I have cleaned and rebuilt all the carbs, which were horrible inside. I'm new to the outboard work but have tools and a shop manual. So like I said, carbs are cleaned and look good. The only issue is that there is a film on the bowl. Have cleaned and cleaned. Soaked and soaked and Its not going anywhere. Moving on....


I am having difficulty with setting float height. I was hoping that there is a simple answer to this on the procedure. The manual seems to be lacking in this aspect. I am then going to be replacing all fuel lines. I pulled the fuel pump as well and will be rebuilding this as well as there is a ton of corrosion on the valves and the gasket is covered in ethanol destruction.

Any help to get this thing back running would be greatly appreciated.

-Sam

I am no expert but I have had the carbs apart on my M90a at least a dozen times as I had issues with disintegrating fuel lines.

My advice would be don't mess with float height adjustment
If the "film" isn't flaking or coming off I wouldn't be worried.
Replace every fuel line, replace complete fuel pump with OEM (I had issues with a non gen part) and reassemble at the same time with a new fuel filter and you should be fine.
Also link and sync your carbs and reset your idle mixture screw (1.5 turns out from memory)

What shop manual do you have? The aftermarket ones, such as seloc are much too general to be of much use. Better to get the actual Tohatsu Factory service manual.

What did you soak the carbs in? Did you soak in a heated ultrasonic cleaner? What sort of film is on the bowl? The carbs are anodized, so you want to keep that. If there is gunk stuck to the castings, that may also be in the passages. Make sure everything is clear. I assume your soaking and cleaning was done with all bits out: no jets, emulsion tube nozzle, or similar when cleaning. After the soak to soften the organic varnishes, then blow out liberally with acetone-based spray. Maybe a whole can per carb.

The float height is always set the same way for any carb: Invert the housing, and the float should be parallel to the casting when the float valve is closed by gravity pressure on the float. I assume you know how to adjust that.

Install a new Factory (OEM) fuel pump.

I can help you with parts, a proper manual, and stuff.

Paul,

I have the clymers tohatsu shop manual. I soaked it in a carb dip that I purchased at Pepboys. I disassembled every removable piece from the carb before soaking. The only thing that seemed to not come off was the plastic where the fuel line goes. Seemed built in. Everything cleaned up and I sprayed carb cleaner through the jets and all other clogged pieces. The carbs were horrible inside.

I have never worked on an outboard, or really any motor for that matter. I am learning from scratch. For the float I just hold the housing so the float is parallel with the housing? And then tight then screw all the way down?

I have not used a ultrasonic cleaner, of coarse I discovered that after the fact. If that is what I need I will look for one. Simply put I'm tired of paying people to work on my motors. I would rather learn it so when something does go wrong out there I can be knowledgable enough to fix.

I'm not sure how I can post pictures of what I'm talking about but on the bowl. There is a slight black discoloration in spots, but you cant feel it with your fingernail, and it's not coming off.

As far as the fuel pump, replace the entire thing? Or can I use what I have and replace internals? It looks like the price for a new full assembly is around $80.

As far as fuel lines seems like each "pipe" is around $10 a piece. Is this the only recommended replacement or can I just find a longer roll of 1/4 inch fuel hose and cut each to length?

All the help is greatly appreciated.

appreciated.

-Sam

OK, Gotcha.

Dump the Clymers manual. I can get you a real one. PM me for that.

Yes, the plastic nipples are permanent, and unavailable. If you bust one, you will be looking for a Weatherhead fitting and a driil and tap, or another carb!

Sounds like the motor sat for quite a while with gas in it. You CAN clean that, but have patience.

Yes, hold the carb body inverted, and the float should be horizontal.

Black discoloration is likely oxidation, or crud from the dip. Don't worry about it.

As for the fuel pump, I would just replace it:




I can help you get that and the manual.

Parts are available, but how long do you want to work on it? I charge $100 an hour; after an hour, it was cheaper to do a new pump.

Thanks Paul. I will Pm you for the manual and fuel pump. Regarding the fuel lines, Do you have a good alternative that you trust other than purchasing each separate "pipe." Also would you recommend replacing the old fuel filter assembly, and possibly adding another Inline, or am I risking restriction at that point? I purchased this motor second hand in 2011. I ran the boat basically year round and did virtually zero maintenance on it for the first few years. the boat has not been run in over a year. When it did run it seemed to bog out and would seem as if it had a fuel starvation issue. I'm sure it is the pump and carbs. I'm paying for the lack of maintenance now, and I owe it to the boat to get it back up to tip-top shape. The trim and tilt is working but it seems to make a creaking sound that I could only explain as dry. The steering helm is now trash and I am contemplating the idea of going with a hydraulic system, any thoughts?

Now that I'm taking care of all these issues, any other maintenance things I should attack now before dropping?


Once all of this is taken care of the boat will be dropped in the water for the season.


sorry for the overload of questions, but I do appreciate it.

-Sam

I typically buy the fuel line in bulk from Tohatsu America. Yamaha has a similar hose, and they are quite good.


If the fuel filter is warped or cracked, I would replace it. Certainly install a new element anyway. Of course, the new filter housing will come with a new element. As for a pre-filter, I use a 10-micron water-separator. They have minimal restriction. If you change it annually, you should avoid a lot of problems with water and some ethanol-related issues.

Lubricate the tilt mechanisms, and make sure your ATF is full for the pump. Hydraulic steering is nice, if pricey, because you can cancel out torque-steer with some of them.

Even BayStar is OK hydraulic.

https://www.wavetowave.com/home/2017/8/22/keep-it-straight-steering-for-outboards

The bulk tohatsu line isn't available anywhere. Any idea for a part # or where to buy the Yamaha similar?

I have some in stock. Any Yamaha or Tohatsu or Merc dealer should have it as well.

pvanv said:

I have some in stock. Any Yamaha or Tohatsu or Merc dealer should have it as well.

Click to expand...

How much is needed to replace everything under the cowling? 4m? Also how can I order from you?

Probably a meter or two, depending on the motor. You can also use the tubing for the pee tube line, etc on many motors. Send me a PM.