The Propshaft: What It is, What it Does, What You Can Do…

An often overlooked and neglected part of your boat motor is the propshaft.  Without proper care and maintenance, the pshaftpropshaft can cause a major headache.  The propshaft is the piece that connects the pinion bearings of the lower gearcase with the propeller.  The two propshaft seals act as covering around the shaft to keep water ane elements from entering the gearcase.  If these seals fail then you could be looking at costly repairs.

It is important to regularly maintain this part of your outboard.  Start when your boat is out of the water or on the trailer. Shift your motor into neutral, remove the key from the ignition, and pull the kill switch in order to prevent any catastrophic injuries.  Begin by getting eye-level with the prop and manually spinning it. If you see any wiggle to the prop as it’s spinning you can know right away that the shaft is bent and needs fixed asap. (Driving on a bent shaft is equivalent to driving a car with a wheel out of balance)

Next give the propeller a thorough inspection.  Make sure blades are on the same plane when you spin it, look for bent blades or big dings in the sides of the blades.  To further inspect the propshaft you will want to remove the propeller (a socket and a screwdriver should suffice). Spin off the nut and lock washer and then you should be able to slide the prop off the shaft.  Behind the propeller will be a thrust washer, you will want to slide this off as well but pay close attention to which was it was put on. You will want to wipe off the thrust washer and inspect for damage. If it looks like the washer has been spinning under the prop then that means the prop nut was not adequately tightened.  

The main goal with all of this is to keep everything lubricated and not damaged.  The prop shaft itself needs to be especially lubricated to avoid the propeller corroding itself to the shaft.  Apply the lubrication liberally as you re-assemble the pieces to the propeller, remembering to put the thrust washer back into place.  In addition to ensuring all the nuts are tightened securely, many service manuals suggest retightening the nut after you’ve run the outboard once and thrust has seated all parts.  


Getting Your Boat Propeller Ready for Winter

Now this may seem counterintuitive for me to tell you how to preserve the life and integrity of your boat prop since my life’sbreakfast work is repairing boat props and I’m essentially teaching myself out of business, but here goes.  :) 

You will need to pull the propeller off of the outboard or sterndrive motor.  Once it is removed you will want to put a fresh coat of grease on the splines.  By re-greasing the splines you are helping to ensure that the prop does not get “frozen” or stuck on the shaft.  (Once a prop is frozen on it is usually a nightmare to get it off and often times the process of yanking it off, using chemicals, and using heat will end up costing you more in repairs)  

There are a variety of different greases on the market today that can help keep your splines & prop lubricated.  You will want to stay away from any anti-seize compounds if you intend to have your boat in salt water since it will cause a galvanized reaction and therefore make the problem worse.  Instead, you want to use a water-proof marine grease. We also recommend products such as, The Mercury Special 101 with Teflon or X2 Tripleguard but you can get away with using cheaper options as well.  Even if you aren’t storing your boat for the winter or live somewhere where the weather allows you to boat year round (lucky you) you will still want to grease the splines at least once a year!   Best of luck and happy boating!


Diameter, Cupping, & Drag... All Keys to a Good Propeller

A term that is important to know when choosing or replacing your boat propeller is diameter.  To determine diameter of your prop measure first determine the circumference (which is the distance around your prop) and then measure from one side propto the other straight across to get diameter.  A majority of manufacturers determine the propeller diameter based on the pitch & horsepower of the boat but diameters are really limitless based on personal preference. A general rule of thumb is; the lower the pitch of a propeller is the larger the diameter will be.  

Cupping is another term that you will need to know when discussing your propeller.  Most propellers have some level of cupping to them, which is where the final trailing edge of the propeller has a bend or curve that tilts away from the boat.  Cupping helps to increase overall performance by increasing pitch which will also lower the rpms. The placement and severity of the cupping determines the rpm and overall performance of the propeller/boat.  

A final term to keep in mind when deciding on the appropriate propeller for your boat is drag.  Drag is the slowing down that occurs when the underside blade is in the water. If vibration and calibration could be controlled a propeller with one blade would be the fastest and most efficient due to a lack of drag (but we all know that it is not a feasible way to create propellers due to many reasons).  As blades are added to the propeller the drag is increased. But the argument for more blades is that it will decrease the time between load and unload time (of water) which will make the process seem smoother. Propellers can come with anywhere between 2 and 6 blades and the ideal number is based on a great deal of factors including pitch, engine capability, and use of boat.  


Fuel Usage: Is Your Prop To Blame?

Have you noticed an uptick in your recent fuel consumption?  Are you filling up more than you were last year? What many propefficiencypeople fail to realize is that boat props are important to efficiency.  When choosing a prop the primary concern should be to make sure it allows the engine to turn up to a speed within the specifications of the manufacturer (usually within 500 revolutions of rpm).  This helps to lengthen the life of your engine as well by not lugging it down or letting it over-rev. There are many other properties to a prop that have an effect on the efficiency for your particular boat including, number of blades, pitch, and skew.  We could help you determine which prop type would be best for your boat that would be most efficient.

In fact, a bent or dented prop can rob you of 10% of your fuel costs right off the top.  We can use our machinery to determine how far out of specs your prop is and can then either repair it or suggest a replacement.  Contact us today! 


Learning About Your Propeller

There is so much more that goes into a boat propeller than most people realize.  There are terms that we in the business use that are often times not understood.  Here is a good overview of a few of those terms to help you better comprehend the work that goes into perfecting your prop: Propeller Facts

What is propeller pitch?

Pitch is defined as the distance a propeller would move if it turned one time through a solid. Think of a screw going into wood. The distance it goes into the wood with one rotation is the pitch. When applied to boat propellers, the concept is a bit more complex since a 21" pitch propeller won't actually travel 21" through water due to variables such as drag, aerodynamics, ventilation, and cavitation. The difference between the theoretical pitch of a propeller and its actual progression in the water is called "slip." For the most part you shouldn't need to worry about either of these unless you suspect that your propellers pitch may be wrong for your boat and your boat motor. In this case, you can try to determine it yourself HERE or give us a call, and we'll help you find out if you have the right propeller pitch. 

What is propeller cavitation?

Propeller cavitation is the formation of air bubbles on the propeller due to pitting on the prop's surface. It usually occurs as a result of damage to the propeller and will be felt in the form of vibrations. Unless you are an expert in propeller repair and have the appropriate tools yourself, cavitation should be addressed promptly with a professional boat prop repair shop as it can damage the propeller itself as well as reducing efficiency and creating an uncomfortable ride.

What is propeller ventilation?

Propeller ventilation is when the prop sucks air, which is often caused by having the boat engine trimmed to high. It can also occur when boating at high speeds and jumping waves or in sharp turns, either of which can bring the propeller close to the surface of the water. Ventilation can cause the engine to over-rev and a signficant reduction in thrust. Unlike cavitation, ventilation issues can often be fixed by the boat owner fairly easily. If you have questions or concern, give us a call!