Winterizing a jet boat: A complete guide for newbie’s

Boating season is fun, and at the end of the season, you need to prepare the boat for the next season, which is winterization. Winterizing a boat is an essential job to do to run the boat efficiently or smoothly for the next boating season.

For the ones who don’t know how to winterizes a boat or the newbies may feel these steps are a little tricky while doing it for the first time. So follow the steps properly to winterize a jet boat quickly and fastly.

Related post – How to winterize a boat trailer: With 9 helpful tips (opens in a new tab). If you have a trailer, then winterizing the trailer is also a must.

1. Clean the boat entirely

Cleaning the boat hull is an essential step to do while winterizing the boat because if there is any growth on the boat hull, it can cause any problems to the hull over time (during the winter). While cleaning the boat, clean the bilge area as well.

First, start with the outer portions and wash the outer portion of the boat completely with fresh water if there are any barnacles stains on the tubes, then use hull cleaners such as Starbrite hull cleaner (linked to Amazon), which removes them easily; no need to scrub them also.

Wash the hull properly with any pressure washer or garden house and scrub the boat hull with the brush to remove any tough stains.

Next, clean the engine bay. For cleaning the engine bay, don’t use a pressure washer because it will flush the water at high speed, and it can damage any electric wires and components in the engine bay, so use a low-pressure hose or garden hose to wash the engine bay.

The essential thing to note while washing an engine bay is not to spray water inside the engine’s air intake, which causes problems if you spray water inside the air intake. The simplest way to prevent that is by covering the air intake with hand or any while washing the engine bay.

After finishing that, you are done with engine bay cleaning and remove all the water in the engine bay (if any).

NOTE: Don’t wash the engine just after finishing the ride. If the engine is hot and if you wash the engine, it will cause problems.

Some cleaning tips for a boat hull

  • Use a microfiber cloth for cleaning the boat. It is a very soft cloth, and you can clean the things well with this cloth. And it will not leave any lint or dust on the surface of the boat.
  • Use any cleaning liquid. Don’t clean the boat only with the water; use any boat hull cleaners or so. If you have any tough stains on the boat, it will remove the stains easily.
  • Use a soft brush for general cleaning and a stiff bristle brush for tough stains. Don’t scrub too hard with a stiff bristle brush; it can peel off the bottom paint (if any).
  • A 50/50 mix of vinegar with water is a good mixture to remove any water spots in the boat.
  • Use the pressure washer (if you have any) and put some cleaner in the soap/cleaner injector place and spray it on the boat. Then wait for some time and then clean with normal water.

A pressure washer will help a lot with cleaning and washing the boat trailer and boat as well. Check the product in Amazon, click here, or click the image below.

After cleaning the boat properly, drain the boat completely. And then, start the winterization process.

Check my article on 11 Simple maintenance tips for a boat: DIY (opens in a new tab). In that article, I mentioned all the DIY maintenance tips you can do quickly to maintain the boat properly.

2. Stabilize the gas

Stabilizing the gas is an essential step to do if you have any fuel left in the tank, because nowadays, all the boats are using ethanol gas (E10 gas), which will create water inside the tank, and that water will damage the fuel tank over time. So, it is good to fill the tank more than 3/4th or full and add a stabilizer to it.

Topping up the fuel tank will prevent condensation inside the tank. And don’t leave the tank empty; it can cause problems (50/50 chances). Stabilizing the gas is an essential step to do while winterizing. Check the product in Amazon, click here, or click the image below.

Stabilizing the gas tank in a boat

  • There are so many brands out there. Choose the perfect one for stabilizing. Now pour the stabilizer liquid into the gas tank, don’t pour the stabilizer how much you want. For every stabilizer you buy, they will give some instructions to use.
  • Based on the instructions on the bottle, use it accordingly. If you use more, then the whole fuel (gas) will gum up. If you use less, it won’t stabilize the gas much. So, use it accordingly. They will tell to use 1oz for 10 liters or something like that, generally (quantity changes from brand to brand).
  • After pouring the stabilizer into the tank, switch on the motor and leave it for some time (like 5 – 10 min). The stabilizer will flow inside all the fuel lines, carburetors, and cylinders, stabilizing the gas.

It’s good to use the stabilizer if you are not using your boat for 2 or 3 weeks. So, you won’t get any problems in the future. If you are storing the gas for a long time, then don’t forget to use a stabilizer.

Check this video on water formation in the gas tank, he explained it well

3. Flush the water inside the engine

Flushing the water inside the engine will remove all the dirt inside the engine, engine exhaust, etc. To pump water inside the engine exhaust, connect the hose to the jet boat’s flush port. For Yamaha, you will find two flush ports (one on the starboard side and another on the boat’s port side).

First, start the engine and then flush or pump the water (essential step). Otherwise, suppose you start pumping water inside the engine before starting the engine. In that case, the water can fill up the exhaust and engine cylinders, damaging the motor if you start the jet boat with water flooded inside the engine.

So, start the engine first and then start flushing or pumping the water for 5 min (for time, you can see that in your user manual). After finishing that, first cut off the water, and then the cut off the engine (essential step). But before cutting off the engine, run the engine at 4000 or 5000 rpm for 5 sec, and then stop the engine so that all the water left inside the engine will be blown out.

Finally, pour antifreeze into a bucket and then start pumping the water into the motor for the last time. Then cut off the water first and increase the motor rpm for 5 sec to pump out the extra water and stop the motor.

Check the Starbrite anti-freeze product in Amazon, click here, or click the image below.

Then drain the jet boat for some time and finally start the engine once more to blow out the remaining water in the exhaust completely. Don’t run the engine for more than 15sec without pumping water inside the engine exhaust because it can heat the engine if you are starting the engine without pumping water inside the exhaust.

One more essential thing to note is if the engine stops while flushing or pumping the water inside the engine, then cut off the water supply quickly so that engine (inside) will not be flooded with water.

Related post – Saltwater maintenance for a jet boat: With corrosion prevention tips (opens in a new tab). If you are boating in saltwater, then you need to check the article to prevent corrosion due to saltwater.

Check this video on flushing the jet boat engine.

Related post – Effects of saltwater on a boat: With precautions, you need to take while boating in saltwater (opens in a new tab).

You can do this while you are starting the engine after pouring the stabilizer in the tank. You can stabilize the tank and flush the engine for around 10 min. By doing that, you will save time.

4. Use fogging oil (in the air intake and cylinder)

After flushing the engine with water, all the motor’s inner walls will contain droplets of water, which will damage the motor’s inner walls if you didn’t get rid of them. By using a fogging oil (it is a lubricant), it will coat all the inner walls of the motor with lubricant to prevent corrosion oner time.

So, a fogging oil will prevent corrosion by coating all the motor’s inner walls with lubricant. Check the product in Amazon, click here, or click the image.

Using fogging oil in air intake and cylinders

  • You can do this process while starting the engine to stabilize the tank and flushing the engine with anti-freeze. The first three steps (stabilizing the gas, flushing the engine with anti-freeze, and using fogging oil) can be done at a time.
  • First, open the air filter and start spraying the fogging oil into the air intake while the motor is running (for 5 – 10 seconds). Repeat the whole process at least two or three times properly until the engine stalls.
  • While doing this process, white color smoke will come out from the engine. If the engine stops while doing this process, it is a good sign. Which means the whole area inside the engine is coated properly.
  • After completing the air intake part, close the air filter with the cap, then stop the engine and open the spark plugs, and start spraying the fogging oil into these holes too. So, the inner layers of the cylinder will be coated as well.
  • While doing the spark plugs part, don’t start the engine completely, just simply press the start button and stop immediately. While doing this process, close the spark plug holes with fingers or something, for coating the inner walls of the cylinder properly.

At that time, check the color of the center electrode of the spark plugs. If the center electrode of the spark plugs is black, then change them. Generally, the white color center electrode indicates that the spark plug is in good condition.

After finishing with the engine part, spray silicon spray (wd-40) (linked to Amazon) all over the wirings in the engine bay and inside the engine bay completely to prevent any corrosions over time. Spraying the wd-40 is an essential step to do while winterizing the boat to prevent any corrosion over time.

5. Remove the batteries off the boat

Just turning off the boat will not prevent the battery from draining. You might not be aware of it, but when your boat is turned off, your battery could still draw power from things such as the radio, bilge pump, even a clock, etc. So, remove the battery from the boat during winterization.

When your boat is stored, these items will slowly drain your battery over time, especially if the battery is wired directly to any of these objects. You should disconnect the battery if you are winterizing your boat.

Removing the battery from the boat

  • First, remove the battery (negative terminal first and then positive terminal). Then clean the battery with any cleaner and get rid of any dust stuck on the battery.
  • After that, check the case properly, and make sure it doesn’t have any bulge or any other cracks on the battery. If there are any bulges or cracks on the battery means, you are overcharging the battery.
  • Next, check the terminal posts. If the terminals are corroded, then clean it up with a terminal post cleaner or any small stiff bristle brush. Next, check the battery posts, clean them if corroded, use any cleaner or soda, and clean them.
  • Every month check them and tighten them up. So, by doing that, you can prevent low voltage in the battery. If they are loose, then you will get low voltage.
  • Then check the distilled water level, and you need to fill it if the level is less. Use only distilled water, not any other water or tap water. If you are using a lead-acid battery, then it is easy to refill the distilled water than a maintenance-free battery.
  • Then check the voltage of the batteries and charge it if the voltage is low.
  • Finally, coat the terminal posts with grease. These are the basic steps to do every once in a season to avoid any problems with batteries. Then store on any rubber surface in the garage or in your home to prevent any battery drain conditions.

Different voltage levels of all types of marine batteries are listed below in the table (source).

Sealed or Lead Acid
battery (in volts)
Gel battery
(in volts)
AGM battery
(in volts)

6. Cover up the boat and use anti-pest

If you are storing the boat outside or in the water, then it is good to cover the boat.

Keeping the boat outdoors without any cover may damage the boat due to the weather during winter. If the water goes inside the boat, then it won’t come out. Anything (any living creatures) could go into the boat if you didn’t cover it. So, cover the boat with any boat cover during winter.

Covering the boat

  • If you are keeping the boat indoors, then no need to worry about covering it much. But, if you are keeping the boat outdoors, then you should cover the boat with boat cover. Covering your boat will protect from elements like dirt, dust, moisture, and any living creatures.
  • Try to remove any organic materials like canvas, leather, or other fabrics to avoid mold and mildew. And any electronics that could freeze should be removed to avoid damage.
  • Make sure that there are no open holes in the boat. Any small creatures can get into the boat from the holes. Then, finally, cover the boat with a strong cover. So, it can withstand any harsh weather.

Check this trailer valet website on covering the boat, where they explained all the steps to do that click here (opens in a new tab).

7. Do regular checks during winter

Regular checks are essential for a boat if you are keeping the boat outdoors. Check the boat every one or two weeks to ensure everything is doing well or not. Generally, in the winter, snow might fall on the boat, clean it regularly.

Check my article on How long can you leave a boat in the water (opens in a new tab) to know all the basic things you need to do to prevent any growth on the boat hull.

Bottom line

By winterizing the boat properly, you can ensure that the boat will be in perfect condition for the next season. By doing it yourself carefully and efficiently, you can save $300 – $400.


My name is Mahidhar, and I am passionate about boating. Every day I learn some new things about boats and share them here on the site.

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