Boat Motor Parts, Outboard Motors, & Boat Propellers

Motor Parts
Motor Parts
Boating Know How

OEM vs. Aftermarket Boat Parts

When buying boat parts, should you buy an aftermarket part, or stick with original equipment manufacturer (OEM) parts?  There is some controversy over this, but the debate is far from being cut and dried. ... read more

Like most others, I once believed that an OEM part was always superior to an aftermarket part.  Unfortunately, the word “aftermarket” seems to carry some negative connotations.  So what are the real differences between an OEM part and an aftermarket part, and where do aftermarket parts find their place in this day and age?

Some time ago, there was no such thing as an “aftermarket” part.  Everything was made directly by the original manufacturers.  Eventually, these manufacturers found it beneficial to outsource production and manufacturing duties to other factories, who were one day also able to replicate these parts and sell them to other distributors.  These parts became known as aftermarket.

When most people think of aftermarket parts, they probably think of a huge production line overseas pumping out mass quantities of low-quality parts.  While this sometimes may not be far from the truth, these parts are usually of a higher quality than one would originally expect.  In fact, these parts are more often than not the exact same part that you would get from an authorized dealer.  The reason for this is that a lot of the original manufacturers use the same factories, and even the same companies, to manufacture their parts.  So what is often the big difference between these parts?  The answer is the packaging the part comes in and the brand that it is labeled as being.

There are several reasons why you might choose an aftermarket part over its OEM alternative.  In this day and age, we find most people going aftermarket for economic reasons.  OEM dealers often get by under the guise that their parts are original and therefore are superior, or that an aftermarket part is cheap and will under-perform and potentially damage your motor.  This enables them to charge astronomical prices in most cases, whereas an aftermarket part is usually far less expensive.

Aside from that, you may be the owner of an older motor or boat and the OEM part is no longer available, but an aftermarket company still makes a replacement for said part. Or you simply can’t find the OEM part in your area, whereas you can easily find and order an aftermarket alternative online.

Perhaps you want to change either the appearance of the performance of your motor or boat from its stock condition and no authorized dealer can help you find what you need.  Maybe your boat is taking too long to plane out evenly and you want to adjust the pitch of your propeller, but an OEM propeller isn’t offered in anything other than what you already have.  Most likely, you can find various aftermarket propellers to achieve this.

These are just a few examples of why you may find it beneficial to go with an aftermarket part.  The debate rages on over which is better and why, but the evidence is clear and shouldn’t sway you from deciding to go aftermarket.  Your wallet and boat may thank you for it!

read less

8 Tips to Keeping Your Boat Motor Cool

Overheating is a major cause of death for marine engines,including gas and diesel stern drives, inboards and outboard motors. In fact some industry statistics say as many of 70% of all premature engine deaths emanate from the malady. ... read more


Saving the day, some modern power plants have engine warning systems that literally sound the alarm when the temperature begins to rise towards dangerous temperatures. When that happens, onboard firmware automatically reduces rpm so the boat can, in most cases, limp home. That technology is a great fail safe. But what would be even better is some kind of plan to prevent the overheating in the first place. With that in mind here are some ideas to keep in mind.
  1. Most of the time engines overheat because the impeller isn’t pumping water to the cylinder block and heads. So naturally it follows - keeping track of impeller health is a good idea. On inboards and stern drives that can be as simple as removing the inspection cover and looking at it. You don’t necessarily have to remove it. Visually determine whether all of the blades are present. And are any of the blades showing cracks or checkering? If so don’t hesitate to replace the worn impeller at once. Not only is it in danger of complete failure, when blades strip off they flow downstream into the engine where they could obstruct cooling flow.
  2.  width=
  3. Another important checkpoint is the raw water filter. Go to the trouble of making sure it’s not plugged. At the same time check all of the cooling system hoses, one at a time. Start at the hull thru fitting. Visually inspect the hoses with a flashlight looking for checkering or cracks, once again, clues that near term failure is possible. Next, squeeze each hose in turn. A cooling hose should feel supple, and not hard. Most of the time when you find a hardened hose it will be on the engine. That’s because ambient engine heat hour after running hour has baked it to a crisp.
  4. Outboard motor impellers are strategically located in the lower unit. The lower unit is exposed to sunlight, which over time can bake the impeller. Baked impellers have lost resilience. Hard impeller blades strip off. Also over time, and this includes inboard and stern drive impellers, impellers lose their flexibility and take a set - meaning the blades don’t stick out from the hub at a 90 degree angle and are curved. When that happens they will still pump water, just not very much. Knowing that, some boat owners make a preemptive strike and remove and replace the impeller every two or three years.
  5.  width=
  6. Another overheating culprit is the thermostat. Sometimes they stick open, in which case the engine may not warm up to its normal operating temperature. And in other instances the thermostat sticks tight in the closed position. The good news is changing a thermostat is easy even for a fumble fingered do-it-yourselfer.
  7. But what do you do when you think the engine is overheating and you don’t have, or simply don’t trust, the temperature gauge? The answer is as simple as the sea is salt. Shut down the engine for safety sake. Then carefully touch the cylinder head. You should almost, but not quite, be able to lay you hand on it. But if it is sizzling hot, there’s an overheating problem. If you’re squeamish about touching a warm engine, no problem, flick some water onto the engine and watch the results. If the water beads up and sizzles away into evaporation, there’s a problem.
  8. There are other high tech solutions worth considering. For about $50 and up you can buy an infrared temperature gun. To use it, simply aim it at the work piece and squeeze the trigger. The temperature display tells you how hot it is. Also you should know about temperature crayons. They come denominated in different temperature ranges. With this method, scribe a mark with the crayon on the work piece. If the crayon residue melts then the temperature is as least the rating of the crayon.
  9.  width=
  10. Besides the temp gauge, outboard motors also shoot an indicator stream that shows the impeller is hard working. Sometimes when the stream stops it means the impeller is dead. Sometimes it just means the indicator streams plumbing is plugged up. That’s why I have a two-foot section of 300-pound monofilament fish line under the cowling tied to the engine. If the stream stops, I jab the stiff monofilament into the orifice and clean it out. If water begins to flow anew, all is well.
  11. Finally, the best prevention for engine overheating is to trust the temperature gauge and monitor it often. Consider rotating the temp gauge so its needle points straight up when registering normal engine temperature. Then if the temp begins to rise you’ll see it carries all brands of impellers, thermostats, hoses, gauges and more.  

    Written by Tim Banse

    Tim Banse is a marine engines expert and has written about propulsion for Popular Mechanics, Yachting, Motor Boating, Boating Industry and other publications around the world. His current pet project, a source for free information about outboard motors, stern drives and inboards. Tim’s articles will be seen here and in the blog, plus always at

read less

Gimbal Bearing Removal and Replacement (Video)

A video demonstration of the removal and replacement of a gimbal bearing on a Mercruiser Alpha Gen 2 Drive assembly. This procedure is similar with other brands of outdrives as well. ... read more

Welcome to Mallory Marine. We’re going to demonstrate the removal and replacement of a gimbal bearing on a Mercruiser Alpha Gen 2 drive assembly. This procedure is similar with other brands of outdrives as well.

Step 1 - Place the outdrive in forward gear.

Step 2 - Make sure the drive is in the down position and as vertical as possible.

Step 3 - Remove the outdrive. Remove the trim rams, the nuts holding the drive, and the speedometer pick up tube.

Step 4 - It is always a good idea to check the engine alignment prior to removing the bearing.

Step 5 – Remove the gimbal bearing using the Mallory Marine puller. Part number 9-79820. Follow the enclosed instructions for an easy removal. For a more detailed video on the puller itself, visit Mallory Marine’s website, or

Step 6 – Install the bearing. Mark the outside face of the carrier to index the grease hole in the side of the carrier making sure the tolerance ring does not obstruct the grease hole. Using the proper mandrel tool, drive the bearing in place making sure you have aligned the mark previously made with the grease port in the transom housing.

Step 7 – Grease bearing. Locate the grease nipple on the right hand lower transom housing and pump grease into the gimbal bearing until you see it coming up around the bearing.

Step 8 – Check engine alignment. Install the engine alignment tool again making sure the alignment is correct. You should be able to turn the tool with two fingers when properly aligned.

Step 9 – Preparing drive for installation. Install “O” ring on yoke shaft and grease spline with spline grease. Install gasket and water passageway “O” ring. Grease shift slide making sure it is properly aligned. Grease u-joint assembly if equipped with greasable u-joints.

Step 10 – Install outdrive. Align yoke shaft through gimbal bearing and into engine coupler. Make sure drive is in forward gear by only pressure on propeller and pushing drive into place. Install retaining nuts, trim rams and speedometer hose.

Thank you for viewing. For further information and parts go to

read less