Being in the industry for over 17 years, I have had the opportunity to see how different parts of the continent perform engine maintenance. By no choice of their own, the northern states and Canada seem to do a better job maintaining their boat engines simply because they are forced to do so.
Every autumn, just about every boat has to come out of the water or the ice on the lake will crush it. During that time most people bring their boats in to get winterized and have their fluids, both engine oil and gear lube, changed. There are still a number of unwise people who choose not to do so, but the majority tend to use fall storage as an opportunity to do routine maintenance.
Now, in the southern states, where it is possible to leave the boat in the water all year round I have seen some horrible practices. One of the worst I have seen was a boat that was 6 years old with the original oil filter still on it. The oil looked like sludge, and from the burnt smell of the gear lube in the outdrive I would say the gear lube was original as well.
I wish I could tell you how often I have heard, “Jason, what’s the big deal? I only put about 30 to 40 hours on the boat a year.” If you went simply by hours, it wouldn’t be a “big deal.” But Mercury/MerCruiser recommends once a year OR every 100 hours. Many people want to compare their boat motor maintenance schedule to their car, but they are not the same. There are a couple of major differences that a wise boater should aware of and take care to note. Look at these comparisons:
1. For the most part, your car runs in a dry environment.
Even when it rains, once the car stops the top of the motor is covered, while the bottom is well ventilated to allow for quick drying and constant air flow from wind/breeze. Your boat is surrounded by water, and it always seems that there is water in the bilge, even when sitting in the driveway with the plug out. So after a week or two you walk out to the boat, open the engine hatch (which does an excellent job muffling engine noise while slowing down air flow and trapping all the moisture inside) and the engine is completely covered with condensation. So if the outside is that moist, what do you think the inside of the engine looks like? Yes, it is vented to allow crankcase pressure to escape (not to be confused with engine compression), but that means moist air will find its way right down to the oil pan which creates sludge. This is the major reason you are advised to change the oil once a year, even if you do not have 100 hours on the motor.
2. The thermostat will affect the condition of the oil.
Another thing that will cause water to get into the oil is if the motor is not coming up to operating temperature. Check out this picture of a thermostat stuck in the open position.
If the motor is not running at the operating temperature due to a thermostat that is stuck open, it is not getting hot enough to burn the condensation caused by the cooling water running through the engine block. Most people do not worry about an engine running cool as they would if it was hot, but it causes water in the form of condensation getting into the motor. This will also cause fuel injected motors to have a higher fuel consumption rate. And I don't know anyone who wants higher fuel consumption.
So now I have made my point on the engine oil, but I still hear things like, “OK, fine, I’ll change the motor oil, but why should I bother with the gear lube?” Many people mistakenly compare the outdrive/inboard transmission/outboard gear housing with the axle or the transmission of their car. They assume that because they go years without changing that oil, the same is true for their gear lube. Again, the water/condensation comes into play, but so much more! So let me ask you:
How often do you think about getting fishing line wrapped around your axle causing water to get in, and gear lube out? I see fishing line wrapped around prop shafts all the time,
and it takes out that prop shaft seal.
When was the last time you saw a car parked with the axle under water for a month? Yet boats sit in slips for months at a time. Water is denser than air, so a seal that will not leak on land from air pressure will still allow water in when submerged.
When you have your gear lube changed once a year, preferably in the Autumn, the technician is looking for water contamination. If there is enough water in the gear housing due to contamination from a broken seal, and it is left in over the winter, it will freeze. This can crack the gear housing, which will cost you a LOT more than a gear lube change does.
Additionally, what is the first thing that comes to mind when you consider purchasing a truck you know has been used to plow snow? Anyone with experience in this will think, “That transmission is shot, or on its way out!” The load on your boat when it is pushing through the water can be compared to a truck plowing snow every time it is in motion. If you want your boat to last, you need to keep the fluids clean and in good condition.
These are a few of the major reasons it is essential to get your fluids changed every year. Again, I recommend (as does Mercury/Mercruiser) doing so at the close of the boating season to see if you have water contamination. Even if there is not enough water to freeze and crack the gear housing or the engine, you don’t want it sitting inside and seizing up bearings or rusting major motor components. Yes, there is a chance of condensation getting in over winter storage time, but that is a very minor risk compared to leaving water in over the winter. This will also clean out all combustion byproducts which also cause damage to the engine when allowed to sit.
Finally, you might be wondering, “Are all oils created equal?” The answer is “No.” Automotive oils are not engineered to function with:
- high levels of moisture
-heavy loads created by boats
-high RPM for extended periods of time
Using the correct engine oil is imperative to maintaining good engine heath. Mercury outboard motor oil and Mercruiser inboard/sterndrive oil contain additives that can stand up to the rigors of the marine environment. They also meet or exceed API service requirements for SJ, CF-4, and CH-4. Mercury synthetic blend is first in class for all durability testing and the industry leader for internal marine corrosion protection.
To keep your Mercury/Mercruiser warranty valid, you must use these oils. Also those with newer Mercruiser sterndrives/inboards with catalyst engines, you MUST use the Mercrusier/Quicksilver FULL SYNTHETIC oil. Using petroleum based oils will drastically reduce the life of the expensive catalysts that are now required by the EPA.
General oil recommendations:
Mercruiser engines with carburetors: either the Mercury/Quicksilver 25w-40 regular oil or the 25w-40 synthetic blend.
Mercruiser Racing engines: see a Mercruiser dealer with a technician certified for those engines.
All Mercruiser Sterndrive Outdrives: I recommend the Mercury/Quicksilver Synthetic High Performance gear lube in the outdrive. The synthetic gear lube can withstand more heat than the Premium gear lube.
Mercury Inboards: consult a certified Mercuiser dealer with your specific transmission/v-drive type. (Velvet Drive, ZF Hurth, or Walter V-Drive) This oil needs to be changed yearly as well. Additionally, a Walter V-drives uses water to cool itself, so it will need to be drained for the winter seasons as well.
Mercruiser Dry Sump racing outdrives: you should find a Mercury/Mercruiser dealership that has a Technician certified to work on them.
Mercury Outboards gearhousings, lower horsepower motors (and older 2 strokes 115 hp and below)
It would be safe to use the Mercury/Quicksilver Premium gear lube in the gear housing but the Mercury/Quicksilver High Performance will work as well if that is all you can find. For Newer Mercury Motors I would recommend the Mercury/Quicksilver High Performance Gear lube in the gear housing A.K.A “The Foot”.
Mercury FourStroke Outboards: Mercury/Quicksilver SAE 10w-30 oil in all engines except Verados but the SAE 25W-40 synthetic blend would be the better choice.
Mercury Verado Outboards: since they are supercharged you MUST use Mercury/Quicksilver 25W-50 Full synthetic oil.
To check the oil level in Mercury outboards, do so cold after the motor has sat for a period of time. Too often I see someone start their motor, shut it off then check the oil. For these motors it can take 2 or 3 hours to drain all the oil back into the sump. I can tell when people do this because their oil level is always too high because they thought their oil was low and added more.
The next blog will cover maintenance schedules for Impellers, Bellows, and other Outdrive checks.
Note: if you have a Mariner outboard it follows the same recommendations as its counterpart Mercury.
Note: Quicksilver is a Mercury label so it is the same product and safe to use without voiding the warranty.
In case you missed our last blog on fuel additives and ethanol check out Tips From the Power Pros: Ethanol Fuel Do's and Dont's
Master Certified Mercruiser Sterndirve
Master Certified Mercury Outboard Technician.