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Yamaha Four-Cylinder Outboard DIY Winterization

Posted 10/23/2018

Yamaha offers a popular line of four-cylinder four-stroke outboards that are used in a wide range of installations in both fresh and saltwater all over the world. From pontoons to center consoles, bass boats to work skiffs and even water taxis, they are great performers and real workhorses. The most popular are the 90, 115 and 150-horsepower models and many are used in climates where they are taken out of service for the winter months.
 
While we always recommend having your engine winterized by a certified 
Yamaha dealer if possible, these engines are designed to make the process easy enough for owners to do the job themselves. We asked Pete Reils, a certified Yamaha technician at Garden State Marina in Pt. Pleasant, New Jersey to provide a step-by-step tutorial on how you can winterize your engine(s).
 
 
Prior to winterizing the engine it’s a good idea to give the boat a good cleaning inside and out, power wash the bottom, and put a coat of wax on fiberglass hulls. The boat featured here is a late model Cobia center console powered by a single Yamaha 150.
 
Before you get started, put together a checklist of everything you’ll need and be sure you have the proper Yamaha lubricants, additives and filters for the job. A list is available in your owner’s manual and the correct amount of engine oil for your four-cylinder model can be found next to the oil fill cap under the engine cowling.
 
The process starts with changing the crankcase oil. Place an oil pan under the lower unit and with the engine trimmed all the way up remove the drain plug located inside the rubber tube below the rear of the cowling.  
 
Pete places a piece of plastic tubing as an extension over the rubber tube to direct the oil into the pan and lowers the engine using the trim switch on the starboard side to start the oil flowing. After the oil has finished draining, replace the drain plug. 
 
With the engine still down, slide the oil pan directly underneath the lower unit and remove the gearcase drain plug on the starboard side to remove the old lubricant. Check the old oil for discoloration or a foamy residue, which is an indication that water could be getting into the lower unit through a damaged seal. The most common cause of this problem is picking up discarded fishing line behind the propeller. 
 
While that gearcase is draining, remove the engine oil filter found on the port side. You can use an oil filter wrench or on these smaller engines a simple strap wrench works fine. Just be careful not to disturb the oil sensor located on the block just above the filter. 
 
  • Moisten the rubber gasket on the new filter with a little fresh engine oil to assure a proper seal and then install by hand tightening the filter until it is snug.  
  • Refill the crank case with the proper amount of Yamaha engine oil.
  • To refill the lower unit with fresh gearcase oil, first remove the vent screw located directly above the drain plug. 
 
Pete winterizes so many outboards he uses a bulk can of Yamalube® Gearcase Oil with a pump. He threads the fill hose into the drain plug hole and carefully pumps in the lubricant until it starts weeping out of the upper vent. 
 
For DIYers Yamaha offers two options­­­­­­­­­­­­—an inexpensive hand pump that fits quart bottles of the Yamalube Gearcase Oil and works exactly like Pete’s bulk pump system, or a plastic tube with threads that match the drain hole so you can simply squeeze the lubricant into the gear case. Reinstall the vent plug until tight, then remove the applicator from the bottom and reinstall the drain plug. (Do not attempt to fill from the top.)
 
For the next step, Pete uses a portable fuel tank with a small amount of fresh gas treated with Yamalube Ring Free, PLUS EFI Engine Storage Fogging Oil and Yamalube Fuel Stabilizer & Conditioner PLUS. Start by placing a hose flusher over the main lower unit water pickups and turn on the water.
 
Then disconnect the fuel hose at the fuel filter by loosening the spring clamp with needle nose pliers and connect the hose from the portable tank. Pump the ball to prime the engine and then start, allowing it to run for 10 minutes at fast idle as the mixture is thoroughly distributed throughout the fuel system and combustion chambers to lubricate the injectors, valves, cylinder walls and piston rings.  
 
When the 10 minutes are up, rev the engine briefly until you see a puff of smoke caused by the fogging oil exit through the prop hub and shut it down. Remove the hose from the portable tank and refit the onboard fuel hose. 
 
Leave the engine down to drain the water from the cooling system and disconnect the onboard flushing hose so that it drains, too. Then reconnect.

Tilt the engine up and use a grease gun charged with Yamaha marine grease to lubricate all grease fittings. There is one on each side of the steering slide forward of the engine, another found on the steering column and one on the shift mechanism where the shift cables enter the cowling. 
 
To finish the job, spray the entire engine with Yamashield to repel moisture and prevent corrosion, and replace the cowling. The engine will be ready to go when spring rolls around. Y