Change fluids end of season or beginning of season?

MHorn0817

Active Member
May 16, 2021
205
Bowie, MD
Boat Info
1998 215 Express Cruiser
2011 260 Sundancer
Engines
5.7 Mercruiser Thunderbolt w/Alpha I
350 Mag MPI w/Bravo lll
Getting ready to winterize our first year 1998 sea ray 215 express cruiser with 1993 5.7 merc carb motor and alpha one outdrive. Reading as much as I can about winterization process and what to do. Ive read about changing oil in motor and drive to winterize. I was just curious as to why change the oil to winterize instead of in the beginning of the season, so it's fresh at the start of new season.
 
Engine oils build up contaminants and acid from their normal operations. Filters can't remove acids. You don't want the acid-laden oil to be sitting in there all winter - it's far better to have fresh clean oil in there. If there's any water intrusion to the oil it's better to change it before winter layup too. The new oil will still be fresh in the spring; freshness in this context is a matter of being clean and not having much of any engine hours on it.

Similarly, if you got any water in the outdrive oil you want to get than changed before layup. You definitely don't want water in the drive all winter corroding things, or freezing. As a side benefit, any issues detected can be scheduled for repair over the winter rather than in the spring.
 
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That makes sense then. I'll be sure to change the motor and drive oils.

When I flush the motor, should I remove all the plugs and thermostat housing and dump antifreeze down hoses and thermostat hole or should I just run antifreeze through the muffs until it comes out the exhaust?
 
After you fog... Remove plugs. Poke/verify to ensure no blockages a few times. Take hoses off at the t-stat housing - no need to take housing off. Pour antifreeze into block hose, intake hose and manifold hoses until they fill and/or solid pink exits the drive. That's it. This method is better than using muffs.

Lot's of info about this on this site that you can search for if you want more reading material.
 
Okay, I'll do that method instead.
Is it okay to spray fogging oil down the carburetor? Does it have to be fogged?

Yeah I've been reading and googling, trying to find the most accurate and best for me and my boat.
 
Spraying fogging oil down the carb is perfectly fine - that's the only way to spray it in.
 
Should I spray enough to try and kill it or just make it stumble or just use a whole can?
 
On my outboards I would spray to make it stumble then recover, then spray until it dies. That would ensure you get fogging oil in the entire system.
 
Ah okay, so I should hook water up to it and turn hose on, start the boat, while it's idling spray fogger down the carb until the boat smokes/stumbles/dies. Turn boat off, turn water off, remove drains and petcocks at bottom of the motor, poke inside drains and petcocks, remove 4 hoses from thermostat housing and dump marine antifreeze down them until it comes out of drains and outdrive. Put drain plugs and hoses back on.

Suck oil out from dipstick tube, remove oil filter, install new oil filter, put new oil back in, remove water separator, install new water separator, and then be done with winterization of the motor.

Then I need to drain outdrive fluid and put new outdrive fluid in. Anything to outdrive or motor that I'm missing?

From what I read, 15/40 Mobil Delvac is good to use for oil or the 25/40 super tech or quicksilver. I'm still trying to figure out which oil filter and water separator to get, I've read about different part numbers. Does anyone know or is there a site that could tell me which filters I need? As well as which kind of spark plugs I need for unwinterization?

The motor is a 1993 350 mag. Serial number D854451.

Thank you for all the help and tips in advance.
 
You nailed it in that order. On your valve covers should be a factory sticker lists plug type. AC something. Dont get fancy, dont need NGK iridium 100k mile plugs. You’ll be replacing every spring.
 
Ah okay, so I should hook water up to it and turn hose on, start the boat, while it's idling spray fogger down the carb until the boat smokes/stumbles/dies. Turn boat off, turn water off, remove drains and petcocks at bottom of the motor, poke inside drains and petcocks, remove 4 hoses from thermostat housing and dump marine antifreeze down them until it comes out of drains and outdrive. Put drain plugs and hoses back on.

Suck oil out from dipstick tube, remove oil filter, install new oil filter, put new oil back in, remove water separator, install new water separator, and then be done with winterization of the motor.

Then I need to drain outdrive fluid and put new outdrive fluid in. Anything to outdrive or motor that I'm missing?

From what I read, 15/40 Mobil Delvac is good to use for oil or the 25/40 super tech or quicksilver. I'm still trying to figure out which oil filter and water separator to get, I've read about different part numbers. Does anyone know or is there a site that could tell me which filters I need? As well as which kind of spark plugs I need for unwinterization?

The motor is a 1993 350 mag. Serial number D854451.

Thank you for all the help and tips in advance.

Get her up to operating temp and then change oil and filter before fogging.
 
You wrote about putting the plugs in AFTER you pour the AF in. Wrong order. Instead, pour about a half gallon of AF into the large, block hose - and you'll see it come out the block where the plugs are still removed. You're wasting a half gallon by doing that, but it double checks that you got all the water out. Then put all your plugs back in and fill things up with the AF.

As far as the parts go... make it easy on yourself and save all that googling. You must have either a local boat store (or Merc shop) nearby or even a Walmart. Mercruiser (only available at certified Merc shops) and Quicksilver are the same thing. Merc packages it under the Quicksilver label to be sold at retail stores. Just go to one of those places and pick up your stuff. Since the engine is a '93, you probably don't have the remote-mounted oil filter. Keep it simple - just get the Merc filters - the difference in price is extremely negligible and the filters are of (known) good quality. You can spend hours and hours and hours researching other brands (and there are, of course, other brands that are good, too). But I assume, like most of us, your time is worth something.
 
Yes, do the oil change first. You want to start the engine after the change to check for leaks around the filter and spread the new oil aroud. As for filters, everyone has an opinion. I like NAPA gold these days.
 
Yeah I was just going to get quicksilver filters, I'm just not sure the part number I need for the filters because I seen a couple different number options.

I don't have a sticker on my cover or motor so I'm sure what plugs to get yet.

Okay I'll heat motor up, turn off, change oil and filters, pull drain plugs, pull hoses, flush antifreeze through, install plugs and add antifreeze until full, install hoses.

What do I use on outdrive? How do I change fluid?

Do I put anything in my fuel besides stabil?
 
I don't know (memorize) part numbers off hand. If you go to a Merc shop, they'll look it up for you if they don't already know. If you're buying from Walmart, look at any online parts store for part numbers. Part numbers change overtime because they get superceded. Old part numbers would still be valid, though.

Drain the outdrive fluid, pump it back in from the bottom. Replace the two seals/washers as well.

Stabilizer should already be in the fuel - you want that to have gone through the carb.
 
A little more detail on the outdrive. There will be 2 plugs, an upper and a lower. You need to open both in order for the fluid to drain. Open the bottom first then the upper. If you do the opposite you'll likely get a gush of oil on your hands. Let it drain into a pan for a while.

When refilling, get a bottle of compatible drive oil and a pump kit - this makes refilling soooo much easier. The pump will screw onto the bottle and have a hose that screws into the lower drain hole. Always fill an outdrive or outboard leg from the bottom (for ease of service reasons). Pump in the oil until it starts to come out the top hole. The insert the upper plug (with a NEW washer!). Remove the pump hose and install the lower plug (again, with a NEW washer!). You can hold a thumb over the hole if you need a moment to install the plug. Doing it this way blocks air from getting in the drive and letting the oil drain out while trying to get the plug installed. Resist the temptation of reusing the plug washer; reusing it risks water entry past a compromised washer.

71-HhpVsoiL._AC_SL1500_.jpg
 
For the fuel, Stabil works. I personally like Startron fuel treatment. It claims to help prevent phase separation of ethanol gas. This is where the ethanol alcohol in fuel absorbs moisture then precipitates out to a layer of water in the bottom of the tank. It's...inconvenient.

There are some that think Startron's claims are bunk and doesn't work. I'll just say that I used it regularly for 10+ years and had no fuel-related issues.
 

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