Thursday, February 17, 2011

Outboard Shaft Length

A few days after my last post I heard back from the repair shop and the outboard is shot. With a fair amount of effort and money I could probably get it running again, but there are several things that, if they went south on me, I would be hard pressed to find parts and could easily have it become a money pit.

As a result I am selling a 1957 Johnson outboard if anyone is interested. And I am in the market for a new outboard engine.

During the process of researching motors and what to get I learned some important things about purchasing outboards. One that I thought was rather useful is how to determine your shaft length.

Why You Need the Right Outboard Shaft Length
Choosing the right shaft length allows your boat to perform efficiently and reduce the chances for damage to your outboard motor and/or propeller.

The best way to think about choosing your motor is to think about what happens when you are cruising through the water. As your boat gets on plane the majority of your boat is actually out of the water with only the very bottom skimming across the top.

While on plane it would be unwise to have your propeller coming out of the water, or too close to the surface. It would be like spinning your wheels on ice, you just aren't going to go anywhere fast. The other extreme is that you don't want the propeller to be too far under water. A prop that is too far under water is will try to both push the front of the boat up into the air, and will create more drag on the motor.

As a result, the aim is to have the bottom of the cavitation plate even or just below the bottom of your transom.

Fortunately shaft lengths are measured with that in mind:

How to Measure for Outboard Shaft Length
The easy way to measure shaft length is to simply measure from the top of the boat transom to the bottom of the boat. On an outboard this translates to the distance from where the mounting clamp bracket rests on the transom to the bottom of the cavitation plate.

Shaft lengths come in 5" increments, with the short shaft being 15". As long as you are within an inch or two of the shaft length measured on your boat you are in business.

Wednesday, February 2, 2011

Outboard Engine Update

I took the outboard to a repair shop today. I had considered trying to get a manual and then trying to restore the outboard that way. However, I am not a mechanic and with an engine that hasn't even been run in several years I wouldn't even know where to start.

Keep in mind the last time this aluminum boat was registered was back in the mid 1960's and for all I know it hasn't been run since then.

Given the circumstances I thought it would be best to get the outboard up to a base level and then work from there. I also have a lot to get done on the boat itself without spending significant time and money trying to teach myself how to get a boat engine running.

Regardless I was able to learn the year of the engine: 1957. This means that this motor is more likely to be the original one for the boat, and that the age of the boat itself is probably older than I thought.

Should hear in the next few days what they find. If it is just a matter of cleaning out the carburetor it shouldn't be a big deal, but there are a lot of parts that you just can't find anymore for this particular outboard motor.