Parts motor?

I've posted about this motor before, a 92 Nissan N9.9b2, but I now think I it's done for.

Here's the list:
1. Water check port clogged with corrosion. I've tried to ream it out with a stiff wire, even tried to drill it out but stopped because it didn't seem like the drill was going in straight.
2. Motor surges wildly at WOT, then dies. I'm thinking fuel pump. Parts and carb kit are no longer unavailable.
3. Gear oil leaking below the prop.
4. Probable corrosion throughout. This motor has seen a lot of salt and probably gone without a flush.

I could do the carb/fuel pump if there were parts, and a water pump/impeller, but I'm not qualified to get into the gear case, especially if replacing lower unit seals requires much disassembly. A decent used motor would be cheaper than to have a shop do the work and the corrosion might cause more trouble down the road. It idles fine, ran sort of OK on the lake, until it started surging and dying at WOT. It has decent compression 100/105.
I think I know the answer.

I see a lot of older, affordable Johnsons and Evinrudes, and Mercs that are claimed to run well...but it's hard to tell if they've been maintained at all.

Lesson learned.

The corrosion is the only thing that would concern me.

Lower units aren't that hard to work on if you are mechanically inclined, but seals can be pricy.

I resealed a couple lowers this year and just the seals was around $100. Not that you need to replace every seal, but since you have it apart....


An alternative to replacing every seal is a vacuum/pressure pump which can help isolate which seal is bad, but a decent unit is $50-60 or so. This can also help check your crank seals for the surging problem, but you would have to make up plates to block off the various areas of the engine, ie exhaust and intake.

If you have no love for the motor than selling it off as a parts motor might be in your best interest.

Thanks Sailbad (love that). The Seloc manual makes installing a new propeller seal seem semi possible, but pretty involved. Although I'm a halfway decent bicycle mechanic, it's probably not a good idea for me to attempt this, given my tendency to lose parts and reassemble things upside down and backwards the first time around. The seal might not even be available. But, if it's going to be a parts motor, I could attempt this just for practice and maybe it is just the seal at the prop. That is where the oil is leaking from.

I have no reason to love this motor. Think I could get a couple hundred bucks for it...I didn't think so.
Any suggestions on a used motor that has a decent reputation if it's been taken care of? Every motor for sale "runs great!". The motor came with a 16' Valco.

The older Nissans have a good reputation and a lot of people are looking for them - in good condition, of course. I don't think parts are a problem, although it doesn't take a lot of parts before you end up paying for a used motor.

The internal corrosion would be an issue that could make this not worth repairing. Lower units are pretty simple mechanisms. I wouldn't hesitate to tackle replacing the seals in a lower unit. Your surging is a fuel issue, carb rebuild, or a vacuum leak. The fuel/carb issue is easy. A vacuum leak can be simple or complicated.

I'd probably waste an hour trying to figure out the surging and remove the cylinder heads to get a look at the internal corrosion. Depending on what I found, I'd either start repairs or strip the electronic parts, prop, fuel pump housing, and a few other parts and see if I could sell them on ebay. You might cover half the cost of a used motor.

Carb parts are NLA. I've been all over the place looking, Boats.net, etc., nada. There is a Tohatsu dealer here in Portland so I'll make that longshot call. I'm going to try to offload the whole motor unless I get a hankering to take it apart, which might be kinda fun, but I don't have a nice warm shop and I'd rather go steelheading. Thoughts on what motors to consider?

Marine engine has always had whatever I needed if you haven’t tried them yet.

As far as used motors I’m partial to Evinrude/Johnson myself. Cheap and plentiful.

The motor as is in my area would bring probably $100 and I’d give you that sight unseen, maybe more if the paint and decals were in good shape.

I might take $100, if you pay the shipping from Oregon, lol.
What would be your solution for the NLA Carb parts? Jets, gaskets and so on.
Would it be possible to replace that prop seal without taking the whole lower unit apart?

And thank you so much for all the answers. Wish I had more skills, or the time to learn them.

Uncle Krusty said:

I might take $100, if you pay the shipping from Oregon, lol.
What would be your solution for the NLA Carb parts? Jets, gaskets and so on.
Would it be possible to replace that prop seal without taking the whole lower unit apart?

And thank you so much for all the answers. Wish I had more skills, or the time to learn them.

Click to expand...

You can usually replace the prop seals without pulling the carrier, which is not usually not hard but may be difficult considering the corrosion. I had a heck of a time with pulling on my Suzuki DT75, and it is not badly corroded at all.

You can drill a small hole in the seal and pull them with a sheet metal screw.

So the seal goes in from the front, after pulling the prop? It looks like there is a housing of some kind just behind the prop that's held on by two bolts, which looks like it would have to come off but it sounds pretty easy. If I can find a new seal. I should check to see if I have water in the oil.too. What is that seal called? That will help when I go looking for it.

Possibly prop shaft seal, but it can vary by manufacturers.

The problem is many of the seals in the lower will/can wet that seal if they go bad.

Best bet is to pressurize the lower to ~10psi and spray each seal with soapy water to check them individually.

That type lower “should” be a cassette style where if you pull those two bolts the entire bearing housing and shaft/reverse gear will come out as a unit.

I say “should” as I have worked on similar but not a tohatsu.

Beware going that route will need you to replace the large o-ring on the carrier.

And at that point you might as well do both seals and the o-ring....

And so on...

Righto. I'll see what a pressure tester would cost me and see if the service/parts diagram helps. Are we talking complete disassembly of the lower unit?

Complete or partial depends on what you find and how far you want to go.


Some seals on certain motors require complete dissassembly.

Think I'll sell it as is for whatever I can get and buy a decent used motor, preferably 4 stroke 15-20. Should be plenty for my 1658 Valco. Looks like $1500, ouch, but I won't have to be so worried about having to make it off the river, or not, with 30# trolling motor.

Thank you very much for your input!