Nissan NS5B Outboard Repair

So on the fourth of July, we went to take Pippi & Rocket to the shore. This was our first attempt to start the Nissan NS5B Outboard we got with “The Nauti Oar”, the Zodiac Tender, or “Eustace”. It would not go into neutral to start. We bypassed the lockout mechanism, not too smart but we wanted to see if she would start. The Outboard would start but then would stall out. Additionally, we drained the old gas and replaced it with fresher two-stroke mix. It still would not stay running. So we gave up and determined that I would have to go through the outboard later at the shop. In the meantime we had to row to shore and have our friends take us.

Nissan NS5B Outboard-1
Nissan NS5B Outboard-1

Now, I would like to point out there are two technologies I dislike here, a carburetor and a two-stroke motor. Lastly, what I need to keep in mind is that this probably makes this outboard really light, and that is what I want! What I don’t want is my back to go out lifting this outboard or something heavier.

The Diagnosis and Dissambly – Nissan NS5B Outboard

To start the diagnosis, I pull the cover off the Nissan NS5B Outboard and attempt to determine how the neutral safety switch works. It looks like it’s a rod that moves an actuator up and down in the lower unit. So I attempt to drain the oil in the gearcase housing. To add to the current situation there is nothing but black water that drains out! so next, I remove the gear case because looks like there is something wrong with the actuating mechanism.

It appears that the shifting mechanism is completely seized up. The lack of oil in the unit could be part of the problem? Wait it gets even more interesting.

The issue is the gear case (Crack) – The Diagnosis and Dissambly of Nissan NS5B Outboard

So you can see from the pictures there is a massive crack in the gearcase housing. Additionally, the outdrive PTO retaining ring is broken. So this lower unit is probably junk. The crack was likely from something coming apart in the lower unit. Now what I have to determine here is whether I want to repair this or buy a new one? After a bit of searching, I determined a new five-horsepower four-stroke of similar quality is quite pricey. A used lower unit is like two hundred dollars shipped, and I get to save something and not throw it away. Also, those four-stroke motors weigh a bit more in comparison. Thirty pounds versus fifty.

The gear case replacement (Removal)

First, to start I would strongly suggest that you find the manual for the outboard you are working on. In our case, this is a Nissan NS5B, and it is actually manufactured by Tohatsu. The removal of the gear case is pretty simple. Additionally, you need to drain the oil in the gear case. I already had done this. Next, remove the rubber plug on the midsection to reveal the access nut and clamping mechanism that connects the gearcase shift lever to the actuator in the gear case. You then remove the two bolts (8 and 10mm) that attach the gearcase to the lower unit and pull straight down. Again, I would follow the directions outlined in the manual. Below is the link to the manual for this outboard motor.

I did this before I ordered the part to ensure what I was dealing with from a parts perspective. I’ve ordered a part only to find out I overlooked something critical and wasted time and money.

The replacment gear case ordered

I ordered the replacement gearcase off of eBay and waited for it to arrive. The replacement gearcase was in fairly good condition. There were just a few scuffs. It said it had low hours, but I have no clue how this is determined when there isn’t an hour meter. The only difference is the overall color (Grey vs Blue). The impeller and related parts look to be in great condition. The old gearcase is corroded and in bad condition due to lack of maintenance and being in saltwater. The newly used one is from freshwater and has no signs of corrosion. You can see from the pictures below

  • Bottom View Nissan Tohatsu 5hp Gear Case
  • Impeller Housing Top View Nissan Tohatsu 5hp Gear CaseCase Impeller Housing Top View
  • Nissan Tohatsu 5hp Gear Case Impeller Housing View 3
  • Nissan Tohatsu 5hp Gear Case Impeller Housing View 2
  • Close Up Impeller Nissan Tohatsu 5hp Gear Case
  • Nissan Tohatsu 5hp Gear Case
  • Prop Shaft Nissan Tohatsu 5hp

The gearcase replacement (Installation)

The installation of the gearcase is fairly simple. What I will say is the most difficult part was getting the shifting mechanism reattached and working correctly. There is a picture of the nut below. First, I will say having the motor on the makeshift stand I have was a detriment. You are fighting gravity and a whole host of issues that are better addressed with the motor laying on the bench. Which after struggling for ten minutes or more I abdicated to doing this the hard way. Additionally, when you attach the shifting mechanism. Don’t overtighten the bolt, just snug so it operates the shift mechanism. You will need to adjust this later after you get the motor upright and operate the shift lever mechanism to see if it goes in reverse, neutral, and forward.

Old Gearcase and shifting mechanism

So to adjust the sifting mechanism. I would start in neutral. Do not start the motor while doing this, in fact, remove the safety lanyard and disconnect the sparkplug. If the shifting mechanism is neutral the prop should spin freely by hand. If not then adjust the shift mechanism to accomplish this. Tighten the bolt. Next, Proceed to put the sifting mechanism into reverse. It should drop into gear and there should be resistance on the prop when trying to rotate the prop by hand. Move the shift mechanism back to neutral the prop once again should spin free without resistance. Next, go through the same process for forward. Lastly, when you are done tighten the bolt. Now fill up the Gearcase with 80W or 90W oil. So, on to testing that the Gearcase is correctly working.

The Gearcase Engagement (Testing for correct engagement)

Tank Testing
Tank Testing

First, we start by filling up a five gallon bucket with water and lower the Outboard into the bucket of water. What we are trying to accomplish here is to make sure the engine starts and that the motor, gearcase and impeller/water pump are operating correctly. Secondly, there may need to be some minor adjustments to the sifting mechanism. You can see in the picture above the set up I have for testing. It’s not pretty, but it will suffice what we are doing. Word of caution here I would make sure you have a well ventilated area. I have no idea the mixture ratio that I have. I much suspect it’s less than 40 to 1. Who knows though. The engine starts on the first pull so that is a positive sign.

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