4.5 hp mercury 1981 model can anyone tell me what oil to gas ratio should be?? I'm guessing 1 to 24?? What brand of oil do you recommend??

Most likely one pint to four gallons of fuel. I use only Pennzoil XLF extended life formula. Make sure to use a good quality fuel stabilizer as well. I use Sta-Bil Marine.

I did a Google search for ya...it's a 50:1 mix , which translate to 8oz of oil, to 5 gal of gas. Also, you want to run your engine just alittle bit on the rich side, so a drop of alittle more oil in the mix won't hurt. I have a Yamaha, so I use yamalube. Go with mercury oil or penzoil. Penzoil is pretty good.

Check your math Vito! 8 oz in 5 gal works out to 80-1 the way I figure (128x5=640/8=80). I have always used 12 oz in 4 gal which works out just a bit richer than 50-1

The normal container of 2 stroke oil what ever the brad is 16 oz. container. Use half a bottle, which is 8oz, for every 5 gal of gas. And maybe a drop or two more to be on the rich side. If u use your formula, your way too rich. Do u smoke out your waters with that ratio? I have a 1997 Yamaha 80hp. 2stroke. Ive been running it that way for a long time, never have a problem, never smokes, never stalls, starts up every time. Your math may be correct, but everyone I know that has a 50:1 mix uses 8oz. to 5 gal of gas. Do they make a 4 gal gas can?

Sharon#1...your better off reaching out to Mercury, get the answer straight from there tech guys. We can debate this all day and night. I use 8oz oil to 5 gal of gas. 12 oz of oil to 4 gal of gas just seems to much. Your probably buying a lot of 2stroke oil. Buy stock in penzoil. LOL

In all seriousness Pegsguy, your math is correct, but when I bought my boat , I used 12.8oz of oil to 5 gal of gas, as per previous owner. But I noticed that it was smoking heavily on startup and when idling. So I had to go to the source. My source being this old salty s.o.b who has been boating and fishing longer than Ive been alive. He told me that that was too much oil. Go with 8oz for every 5gal and you'll be alright. That's what I've been doing ever since. And your spark plugs will give u a good indication as to whether your rich or lean.

I'm at work. I work the midnight shift...bored, did alittle more research on my engine. 1997 80 Yamaha C80TLRV. Turns out my engine is a commercial application. That's what the "c" means. It was only made one year. Further investigating, its a precission blend mix. Looking at my shop manual, theres no seperate oil tank, nor is there a real explaination of what precision blend means. So for now I'm going to keep doing what I have been doing.

Like you said Vito, your plugs will tell the story...but remember...a little smoke is better than too lean.

My comment was meant to address the math only. I am a 4stroke guy and don't own any smokers, not even a string trimmer. My last experience was back in the early 80's with an old Johnson snowmobile.  And the last time I checked 4 gallons of gas fit just fine in a 5 gallon can but the reverse is rarely true!

Ok, I've been doing alittle more digging...this is in regard to Yamaha...when Yamaha came on the scene in the 70's, they recommended a 100:1 mix. Back then, most Americans were a custom to using the standard of 50:1. Up until the 90's Yamaha recommended the 100:1 mix, but learned that most people ignored that recommendations including their American tecs. I found this on a Yamaha outboard forum. So with that ratio, and the math...if I use 8oz of oil to 5 gal gas..which is roughly an 80:1 mix, I'm still running a bit rich according to Yamaha's old standard. And yes, when i start my engine, it does smoke, but not a whole lot. Once the engine warms the smoke goes away. My spark plugs I check on a regular basis and there not brownish grey (lean) nor are they black and greasy (rich). There somewhere in between. Knock on wood...knock,knock...I've never had an engine problem. If I ever break down, will u come and tow me Pegsguy? lol It's a joke bud...don't always be so serious.

LOL Vito! I don't know if there is a tow rope long enough to reach from Lk Mich to Jamaica Bay. The boat I fish on goes in the water in April and stays there until early Oct. It's just a bit too big to be hauling around.

I can't believe it...I got an LOL from Pegsguy!! Merry Christmas Tom!

Sharon I really believe that 50:1 is the correct ratio for your Mercury motor. But if you want a good answer from a Mercury type guy and folks that really know. Give the folks at All Waves Discount Marine in West Fort Ann a call at 792-5897. These guys know their Mecury outboards and more. The owner is the best Mercury Marine mechanic anywhere.

My 2003 5hp mercury is 50-1

Ok, everyone got me to thinking about this. I have a 25 hp Mercury that calls for a 50:1 ratio and I have been using a pint of oil to 6 gallons of gas. I was pretty sure I read that some where, so I looked at the back of my oil can. It says that 15.8 ounces of oil to 6 gallons of gas is 50:1. If there is any doubt, all of the quarts of oil I have seen has a chart on the back telling you how much to mix.
Gary