Monday, April 3, 2017

Spring maintenance on the outboard motor

A few years ago, I was at a big retail store to buy yet another lawn mower. I was complaining to the sales guy that lawn mowers these days are such junk, and that I hadn't gotten more than two or maybe three seasons out of the last 4 mowers I'd owned.

He asked me: "How often did you perform regular maintenance on these mowers that kept falling apart?"

I let the words sink in slowly, as I tried to grasp the concept.

"Never," I replied.

He smiled and said, "I think we may be on to something, here."

From that day forward, I have become a believer in regular maintenance for small engines. You can bet I've made a point to take good care of that expensive outboard motor I bought a few years ago. 

Last weekend, I did the annual spring maintenance on the outboard to get her ready for this year's boating season. 

Here's a quick overview on basic maintenance for a Nissan Marine NSF8A3 8hp motor. (It is a re-branded Tohatsu MSF8A3 8hp 4-stroke.)

Draining the oil and the gear lube:
This step was actually a little easier this year, since the motor is bolted to the boat and is up a little higher. It was particularly helpful in draining the gear lube from the lower unit, because the fill and vent screws were easier to access.

The transom saver was a big help in holding the motor in position while the gear lube drained.
Last of the gear lube, trickling from the lower unit.

Refilling the gear lube:
The procedure for this still seems a little odd to me. It's messy, but it works. For those of you who haven't done this before, basically you pump the gear lube into the lower (fill) hole until it starts coming out the upper (vent) hole. Then you replace the vent screw first, followed by the fill screw.

Re-greasing the prop shaft:
I had actually been looking forward to this part since last spring, when I learned a little about propeller pitch. I wanted to see what markings might be on my prop to indicate what its pitch actually is.

Cotter pin, prop shaft nut, and washer all removed from the prop shaft.
The propeller easily slid right off.
The only marking I found on the prop was "F7." This probably indicates the 8.9" diameter, 7" pitch prop that comes as standard equipment on Tohatsu-manufactured 8hp 4-stroke motors.
Old grease on the prop shaft.

Prop shaft wiped clean.

Several websites recommended this Quicksilver 2-4-C for re-greasing the prop shaft.

The re-greased prop shaft.

Refill the oil and replace the plugs:
I didn't bother taking any photos of this part. Basically, you re-fill the oil incrementally until it reaches the desired level on the oil dipstick. You have to be careful, because it's easy to over-fill. (Then you have to drain the oil & waste it, and start all over. Best to just take your time.) Changing the spark plugs is simple & straightforward.

Other things:
As this is still a very new motor that has seen minimal use, I have not yet replaced the water pump impeller. These should be replaced as part of regular maintenance, and I plan to start doing so next spring.

Also, this motor has a very simple in-line fuel filter that can be removed and rinsed. I haven't actually done that, yet, simply because there haven't been any symptoms of problems in the fuel line. I will probably remove and wash it next spring as well.

Here's to a happy and safe boating season, everyone!


  1. Nice info and pictures, thanks for sharing.

  2. Ive always heard 3 years on impellors. That lower unit oil coming out looked brand new, Id be tempted to go two seasons. Do these newer four strokes have the same diaphram rubber fuel pumps as older motors?

  3. Hi Chris! I'm not sure, on the fuel pump.