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winterizing twin Yamaha F150s on Long Island: fog the four strokes or not, and what about the fuel

40°44'N 73°13'Wstarted by trailer_queen_no_moreNov 11, 2025in Outboards, electronics and care6 posts

#1

2013 Grady-White Canyon 271, twin Yamaha F150s, about 900 hours each. boat lives on a trailer in my driveway in Islip from November to April, then it goes in a slip in Great River for the summer. hence the username, it used to be a trailer queen and now it isn't.

i've always paid the marina $1,150 to winterize both motors and wrap the boat. this year i'm doing the motors myself and paying only for the shrink wrap. i've got the service manual, the gear lube pump, new filters. what i don't have is agreement on two things:

1. fog the cylinders or not. old guys at the marina say always. the Yamaha service writer at the dealer told me "not really needed on these if you stabilize the fuel and run it." the owner's manual says to fog for long storage.

2. fuel. full tank with stabilizer, or run it near empty. it's a 200 gallon tank and i hate the idea of 150 gallons of E10 sitting in it for five months.

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#2

Annapolis, Suzuki DF250, so not your motors, but same climate roughly. i fog. it's a five minute job with the spark plugs out and it costs ten dollars of fogging oil. i'd rather do the thing the manual says than explain to myself in April why a cylinder wall has a rust ring.

on fuel, full is the standard answer for a reason. less air in the tank, less condensation. with E10 you add a stabilizer that's made for ethanol fuel, run the motors long enough that the treated fuel gets all the way through the VST and the injectors, then shut them down.

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#3

from the surveyor side: the motors i see with problems after a winter were mostly not fogged or not stabilized, but the bigger single cause is water separating filters nobody changed. change both separators when you lay it up, not in the spring. then the filter sitting all winter is a clean one.

on a 200 gallon tank: fill it to about 7/8, not brim full. leave room for expansion when the sun hits the wrap in March. a brim full tank pushing fuel out the vent onto your driveway is how you meet your neighbor's opinion of you.

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#4

i'm the odd one out. Galveston, twin F150s, same motors as you but 2,100 hours. i've never winterized anything in my life because i fish 12 months a year. the only thing i do different from december to february is put a battery tender on when it sits more than ten days.

which is my way of saying the thing that kills these motors down here isn't the cold, it's sitting. if you are laying them up for five months, do the whole list. i'd do the lower unit oil now, not spring, so any water in there doesn't sit and freeze in the gearcase.

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#5

done, both motors. Thanksgiving weekend, 41 degrees and wind out of the northwest, so not fun. here's what i did, mostly following the Yamaha owner's manual you can download off yamahaoutboards.com:

filled to about 7/8 with stabilizer at the rate on the bottle. ran both motors on muffs for 15 minutes to get treated fuel through. changed both water separators, the engine fuel filters, oil and oil filters. pulled the plugs and fogged, turned them over a few times by hand. lower unit oil on both: port came out clean, starboard was slightly milky. that one is going to the dealer to get pressure tested before April, which is exactly why i wanted to do this myself and see it.

the marina charged $1,150 last year. parts and the oil this year were $412. the milky gearcase might eat the difference, we'll see.

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#6

that milky gear oil is the best thing that came out of this whole thread. a seal that weeps a little in November is a $200 job. the same seal after the water in it freezes is a lower unit.

Outer Banks here, F300. i only half lay up because there are days in January where it's 65 and flat and i want to go. stabilizer stays in the tank all winter and i run it every couple of weeks. no fogging since i keep running it.

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Tagged

  • Yamaha F150
  • winterizing
  • fuel stabilizer
  • fogging
  • Long Island