Mercury 300x oil question

**36Tango** · 11-29-2018, 08:57 PM

The 300x’s on my 28 Skater are bad to the bone. Great torque, fast windup, and an awesome sound. That said, they sure smoke allot. Is there anything that could be done to alleviate some of it? I know that with an etec if you burn a certain oil the mix ratio is cut in half. Is there a new and improved oil since 2004 that could lighten the mix ratio? If there is, can a guy make changes with the oil injection system, or would I need to premix? Either would be worth it to lessen the smoke.

thanks in advance!

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**Glastron1987** · 12-01-2018, 09:30 AM

I like the question. I've used different oils over the years and its seem they have gotten better in this respect, but would consider changing for improvement. In one of my boats I use the oil injection system, in the other I premix. Some oils say they can be pre-mixed at 100:1, which should help, but most people don't seem to trust that.

**vnemous** · 12-01-2018, 09:58 AM

I believe the 300x mixes oil at 250:1 at idle to 40:1 at WOT. Pretty hard to do that premixing. If your getting lots of smoke at idle after warm up you may have other issues JMO

**Glastron1987** · 12-01-2018, 10:18 AM

Wow I didn't realize it when so low at idle.

Originally Posted by vnemous

I believe the 300x mixes oil at 250:1 at idle to 40:1 at WOT. Pretty hard to do that premixing. If your getting lots of smoke at idle after warm up you may have other issues JMO

**johnmiffco** · 12-01-2018, 11:49 AM

btw ur resto turned out awsome,,,love the boat,,,,
the 300x has an electric oil pump system
the older 300pm had gear driven and did smoke lots more than newer x
these motors with the injectors in front of the reeds puddles more fuel at idle than direct port motors
if the bleeder system has a split hose,,,clogged check valve,ect it would smoke more than normal,,, so would have that checked
but if both are smoking same amount doubt bleeder issue
check plugs to see if some are wetter than others,,could have some weak coils also
im redoing a 28 now with same motors going on but modified,,,so will be premixing,,,,

**Motv18** · 12-01-2018, 12:33 PM

It is blue smoke, not white or black. That will tell you what’s smoking. And is it both.

Both i I would suspect wet fuel. Or foggy humid air (the Xs is real bad about water smoke from wet compressor) not something you have to worry about but without air filters you can suck a lot of moisture.

Iirc should it be blue their used to be a screw you could adjust or was it on the diagnostic system. To fix the pump to the right setting. You also could have worn oil injectors or just general erosion in the flow ports.

**Chaz** · 12-01-2018, 02:26 PM

The X oils each cylinder individually just in front of the reed valve. If the motor is flat or tucked under just a bit, a little oil will run down the velocity stack part of the adapter plate and puddle at the bottom of the plenum. when you start the motor / trim up, that oil will run into # 6 and send smoke signals that the King is awake ..

If ya really wanna pizz the tree huggers off, pour a bottle of Klotz octane booster, cotton candy, root beer or grape top cylinder lube in with the next tank full. It gives em something to smell as well as gawk at ...

**kct11** · 12-01-2018, 03:53 PM

You definitely make a "entrance" at a busy launch with a pair 300x motors when they fire off. If I see people looking at that spectacle thats the point I wave the cloud into my face with both arms and give a loud "woooo, that's what boating is supposed to smell like!!" It seems to take some tension off the situation and somehow let the unknowing know it's normal.

**fast1200gp** · 12-01-2018, 03:54 PM

what oil are you currently running?

**vnemous** · 12-01-2018, 05:46 PM

I like bubble gum full scent in mine. Kevin pulls his motor down and all the metal parts smell like cotton candy

**Chaz** · 12-01-2018, 06:41 PM

Pennzoil XLF, Canoli Oil, and Grape Kool Aid ..

Chaz = thinkin I can close my eyes, smell cotton candy and gain three pounds ..

**36Tango** · 12-01-2018, 08:21 PM

Originally Posted by Chaz

The X oils each cylinder individually just in front of the reed valve. If the motor is flat or tucked under just a bit, a little oil will run down the velocity stack part of the adapter plate and puddle at the bottom of the plenum. when you start the motor / trim up, that oil will run into # 6 and send smoke signals that the King is awake ..

If ya really wanna pizz the tree huggers off, pour a bottle of Klotz octane booster, cotton candy, root beer or grape top cylinder lube in with the next tank full. It gives em something to smell as well as gawk at ...

Love it! I will definitely do that! Where is the best place to buy the stuff.

If it does mix at 250 to 1 at idle, I cannot imagine getting the kind of smoke that I do. I know that it is oil, as I leave a bit of a slick behind at the dock if I idle for too long.

**vnemous** · 12-01-2018, 08:51 PM

No if. 250:1 at idle

**Motv18** · 12-01-2018, 11:40 PM

It’s been a good while since I did any efi honestly, but currently the new ones that are computer controled can do what they want. Iirc from when I worked on um so could the efi. Might be wrong on a 300x.

If you let it idle for a bit does it stop smoking.

**Chaz** · 12-02-2018, 01:01 AM

Originally Posted by 36Tango

Love it! I will definitely do that! Where is the best place to buy the stuff.

If it does mix at 250 to 1 at idle, I cannot imagine getting the kind of smoke that I do. I know that it is oil, as I leave a bit of a slick behind at the dock if I idle for too long.

Jegs , Summit , flea-bay , Local Drag Strip if they sell fuel.

If your powerhead(s) are in break-in mode or an oil pump was just primed. It will double oil for 120 minutes.

Most of the time that I do an Exxon Valdez , it's usually a steering or trim cylinder seal, fitting or line that is pizzin in the water. Easy way to find it is to spray everything with Desenex or johnson's ( No relation

) foot powder. Start turnin - trimmin .. what's leakin will get wet and change color quick ..