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Looking for advice on older M70A motor

D

dgeesaman

New member
I go fishing each year with a retired fellow. We use his runabout boat that has an M70A s/n 13133. I don't think it has very many hours on it. Each year for the fishing trip it gets some TLC and runs ok, but there are ongoing issues. He takes it to a mechanic every year but I really can't tell if they're doing a good job with it. Given the cost of labor and his budget, I can't imagine they are doing very much. I'm trying to determine if some time and DIY will bring the condition up or if this old piece is just mostly dinosaur. I've never worked on an outboard but I do manual transmission rebuilds and maintain my own cars so I'm comfortable with detailed work as long as I have some documentation.

1) Fuel/oil/grease leaks. I see oil/grease leaking from the split between the motor case and the lower unit. Each time we start the motor I see a thin sheen of something rising in droplets to the surface of the water. I also see what looks like oil in the bottom of the engine case.

2) It runs poorly at times. I think it's mostly tied to bad / old fuel. I would love to know what practical steps can be taken to winterize it so that next year this doesn't take up our time.

3) Can I get a Factory Service Manual? I contacted the online outboard shops and none of them sell this new. Anywhere I can snag a used copy?

4) Is there some clear point in the life of the motor where it's just time to shop for something newer?

Thanks,

Dave
 
1. Probably typical unburned fuel/oil mix. You could de-carbon the motor if you want to.

2. See http://www.tohatsu.com/tech_info/winterize.html

3. Any dealer, including me, can provide you with a factory service manual, Part # 003-21035-1, $44.17.

4. Your motor is dated, and the wp impeller (and associated parts) are no longer available from Tohatsu; you could try sending a PM to kat69 on this board to see if he can cast a new one for you. If the compression is good, you should be OK until you can no longer get needed service parts.
 
pvanv said:
1. Probably typical unburned fuel/oil mix. You could de-carbon the motor if you want to.
Click to expand...

So you figure it's spitting out the exhaust? Can I hook up a hose to the water inlets and do a de-carboning on dry land?

What's involved in replacing the gasket between the motor and lower unit?

David
 
Sorry, I misunderstood; when you referred to the LU, that has a specific meaning to us tech guys. I guess you mean between the driveshaft housing and the powerhead... There are two gaskets; one above and one below the engine base casting. Most common is some carb spitting near idle, resulting in a little oily accumulation in the lower cowl. Yes, you can de-carbon on muffs.
 
Good luck if you need parts as I have the same motor and have been trying to get carb kits and I am told that they are no longer avaliable.
 
tohatsu_guru said:
And you can't fly on Pan Am anymore either. Thing's change, stop whining.
Click to expand...
Dredging up an old thread here:

While I appreciate this is true, this boat belongs to a retired fellow who gets out fishing one, maybe two weeks per year. The hours on this engine are minimal and buying a new engine is prohibitive. Even if he put the cash down he'd never get good use out of while he's still mobile enough to enjoy it. It is eye-opening to see how quickly parts go obsolete with outboards. I guess it's not much different than car parts, except that most of us have a hard time getting the use out of an outboard that we can with a car. With the 4 strokes I can imagine this is going to become even more difficult.

When I own my own boat I'm certainly going to do my best to buy an outboard brand that has a better parts / obsolescence record than most, and stock up on consumable parts/gaskets once it hits 10 years old.
 
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