496 mag dos and don'ts
09-02-2017, 05:37 AM
#2
Registered
iTrader: (8)
I believe your referring to the NLA Cam sensors for the early 496s. It will be serial number dependant which sensor yours will have. IAC valves going bad is another common problem. Keep your flame arrestor, throttle body and iac muffler clean to prolong lifespan. If an IAC fault is found do not continue to run the engine as it can damage the PCM 555. Heat exchanger endcap gaskets need replaced often. They deform and are pulled into the exchanger body. If not replaced they can tear and be sucked into the water system blocking flow.
These are just a few known common problems. Member BUP here has posted hundreds of posts on 496 problems/fixes. Search his username and you'll find a wealth of info.
Mine turned over 530hrs last weekend. Follow all maint intervals especially storing the fuel system if not frequent use. I wanted "turn key" boating, biggest reason I opted for this engine. Properly maintained it has utterly fulfilled my request.
These are just a few known common problems. Member BUP here has posted hundreds of posts on 496 problems/fixes. Search his username and you'll find a wealth of info.
Mine turned over 530hrs last weekend. Follow all maint intervals especially storing the fuel system if not frequent use. I wanted "turn key" boating, biggest reason I opted for this engine. Properly maintained it has utterly fulfilled my request.
09-02-2017, 10:19 AM
#3
VIP Member
500+ hours on mine when I sold them, and I never had any big complaints; and I never had one let me down.
-Crank Sensors can have issues; good to go ahead and have a pair of them on hand.
-Cam Sensors can have issues, and yes the Cam Sensors (black in color type) on your engines are NLA from Mercury (UNLESS they have been cut over to the new style, which requires a pigtail change AND the timing chain cover to be replaced). (There are other threads on this. You can find them out there; sometimes eBay; and even though I bought a pair for my engines, never had an issue with them.)
-They are ethanol "sensitive", meaning, IF you have ethanol 10% fuel, make CERTAIN that you keep the fuel treated with StarTron or similar. I had a bout where I didn't know I got ethanol fuel (mislabeled); stored it in the boat for a few months while in humid Florida; and it did ruin my fuel pumps, fuel filters, and fuel/water separators. Check your fuel plumbing for the "inline fuel filter" which looks like a giant D-cell battery. Overall, those Mercury filters are JUNK, but you can switch them out to a Wix/Napa unit which will require new hose barbs.
-I actually REALLY like and prefer the fuel/water separator setup on the early 496s which is a unit that installs like an oil filter. Change them at least every season.
-Change the oil and filter every 25 hours or so. Mobil1 15w50 and a quart of Lucas Oil Treatment Synthetic and Wix Racing/Napa oil filters was my "recipe" that worked perfect for me.
-Change the plugs every 100-150 hours. Make sure the spark plug wires don't have any burn marks from the manifolds.
-Make sure you do a FULL winterization on them; with Anti-Freeze just like you would any other boat. No need to warm the engine as their is no thermostat on the sea water side. The air-pump-actuator drain system is NOT for winterization, merely to extend your boating season into the colder weather.
-Also, you can't fog these motors like a carb setup. You "fog" them buy mixing up a "cocktail" of 2-stroke oil and gas. This is discussed in the manual, and BUP here on OSO has talked about it. The easiest way to do this on the early 496s is remove the fuel water separator, dump out half the fuel, fill it with 2-stroke oil, and run your last 3 gallons of antifreeze though it.
-Clean the flame arrestors with something like carb cleaner or the like; a bucket of water and a brush, and make sure they are dry before re-installing. All you are really cleaning off of them is belt dust.
-Good to have a spare pair of IAC on hand too; they do go bad every once in a while.
-Make SURE the heat exchanger is clean. If this is a new to you boat, I would suggest ordering a new set of heat exchanger gaskets, removing the end caps, and making sure your heat exchanger end cavities are clean, and you can see though all of the tubes. The heat exhanger end cap gaskets can and do distort and can block cooling. There are other posts on this.
-I did have my starters replaced once, due to the starter bendix shaft corroding and not engaging the flywheel. I paid someone to do this, PITA.
-My MOST IMPORTANT piece of advice is to buy a Rinda scanner, www.rinda.com; and keep it on the boat. The computers on these boats will point you toward your problem 85% of the time.
-Crank Sensors can have issues; good to go ahead and have a pair of them on hand.
-Cam Sensors can have issues, and yes the Cam Sensors (black in color type) on your engines are NLA from Mercury (UNLESS they have been cut over to the new style, which requires a pigtail change AND the timing chain cover to be replaced). (There are other threads on this. You can find them out there; sometimes eBay; and even though I bought a pair for my engines, never had an issue with them.)
-They are ethanol "sensitive", meaning, IF you have ethanol 10% fuel, make CERTAIN that you keep the fuel treated with StarTron or similar. I had a bout where I didn't know I got ethanol fuel (mislabeled); stored it in the boat for a few months while in humid Florida; and it did ruin my fuel pumps, fuel filters, and fuel/water separators. Check your fuel plumbing for the "inline fuel filter" which looks like a giant D-cell battery. Overall, those Mercury filters are JUNK, but you can switch them out to a Wix/Napa unit which will require new hose barbs.
-I actually REALLY like and prefer the fuel/water separator setup on the early 496s which is a unit that installs like an oil filter. Change them at least every season.
-Change the oil and filter every 25 hours or so. Mobil1 15w50 and a quart of Lucas Oil Treatment Synthetic and Wix Racing/Napa oil filters was my "recipe" that worked perfect for me.
-Change the plugs every 100-150 hours. Make sure the spark plug wires don't have any burn marks from the manifolds.
-Make sure you do a FULL winterization on them; with Anti-Freeze just like you would any other boat. No need to warm the engine as their is no thermostat on the sea water side. The air-pump-actuator drain system is NOT for winterization, merely to extend your boating season into the colder weather.
-Also, you can't fog these motors like a carb setup. You "fog" them buy mixing up a "cocktail" of 2-stroke oil and gas. This is discussed in the manual, and BUP here on OSO has talked about it. The easiest way to do this on the early 496s is remove the fuel water separator, dump out half the fuel, fill it with 2-stroke oil, and run your last 3 gallons of antifreeze though it.
-Clean the flame arrestors with something like carb cleaner or the like; a bucket of water and a brush, and make sure they are dry before re-installing. All you are really cleaning off of them is belt dust.
-Good to have a spare pair of IAC on hand too; they do go bad every once in a while.
-Make SURE the heat exchanger is clean. If this is a new to you boat, I would suggest ordering a new set of heat exchanger gaskets, removing the end caps, and making sure your heat exchanger end cavities are clean, and you can see though all of the tubes. The heat exhanger end cap gaskets can and do distort and can block cooling. There are other posts on this.
-I did have my starters replaced once, due to the starter bendix shaft corroding and not engaging the flywheel. I paid someone to do this, PITA.
-My MOST IMPORTANT piece of advice is to buy a Rinda scanner, www.rinda.com; and keep it on the boat. The computers on these boats will point you toward your problem 85% of the time.
Last edited by Sydwayz; 09-02-2017 at 12:36 PM. Reason: readability
09-02-2017, 12:34 PM
#5
One more thing:
Make sure your antifreeze is BRIGHT pink/coral in color. If it starts to turn dark/metallic, it's time to be replaced. The antifreeze is only good for 6-7 seasons, per Mercury & the manual. There are block drains you need to pull to drain all of it. When it starts to turn dark/metallic, it is silting up, and not flowing as well; affecting your cooling.
Make sure your antifreeze is BRIGHT pink/coral in color. If it starts to turn dark/metallic, it's time to be replaced. The antifreeze is only good for 6-7 seasons, per Mercury & the manual. There are block drains you need to pull to drain all of it. When it starts to turn dark/metallic, it is silting up, and not flowing as well; affecting your cooling.
