Rebuilt 2 stroke burning a lot of oil, won't run at idle during break in period

[Oldham22]

I have a 1998 145HP 2 stroke and I had the engine rebuilt. The manual says to have a 50:1 ratio to break it in, and I have followed the instructions closely for the first tank of gas. If the gas gauge is accurate, I still have ~ 1/4 tank to go.

It was smoking at idle, which is understandable. After about 5 hours of running it, over the course of two days, I docked it for about an hour. When I tried to restart, smoke poured out, it would start for a few seconds and then immediately shut down.

When I gave it a lot of gas, it seemed to be able to run, but it would shut down again when I lowered the RPMs. I was in a very busy area, with a long way to go at no wake speed (at least 20 minutes) so I couldn't open up the throttle. I was also near a restaurant with lots of outdoor seating so it would be very uncool to rev it up while docked because of the excessive smoke.

I had about 25 gallons of fuel in the tank when I added the oil. Could the oil & gas have not mixed well (oil basically floated) and it's now burning a much too high a ratio of oil to fuel? Can I just add some stabilizer and top off the tank? Should I drain the gas out and start fresh? Could there be carb or spark plug issues from less than a tank of gas?

[Murray]

Your fuel pick up is at the bottom of the tank so if the oil is “floating” then you would not be getting any oil. The oil should mix with the movement of the boat. I’d suggest you get a portable gas tank, measure the exact amount of fuel and oil at 50:1. Your comment, “ I had about 25 gallons of fuel...” indicates that you don’t really know what your fuel to oil ratio is. With your description of the engine smoking I’d suggest your spark plugs are fouled, give them a good cleaning before you try an exact 50:1.

[Solarman]

Are you still using the oil injection system? How many gals of fuel does your tank hold? I'm guessing your tank holds about 100 gals and 1/4 left. If using oil injection system mark the level, and try adding 8 - 10 gals of fuel plus stabilizer, if it stops smoking add some oil. And yes, check the plugs. It does sound like your injection system is adding oil? But it's difficult to tell that from this side of the screen? You have to give us more info to be sure.

Your idle-air-mixture screws should all be set identically at the Suzuki manual required adjustment. You can adjust the idle-stop setting a little higher during the heavier oil period if you need to.

Post back on what you have. Good luck.

[Oldham22]

Thanks for the replies.

It only holds 30 gallons of fuel, so I've probably only got about 6-8 gallons left. Yes, the oil injection system is still working. Should I have taken that into account when calculating the 50:1 ratio? When I said I had about 25 gallons of fuel, that is because I have a 30 gallon tank, added 76 ounces of oil, and then topped the tank off and it only took a little over 4 gallons. Should I have added less oil directly to the fuel since the oil injection system was already adding oil?

Also, I had new fuel in the tank when the engine was rebuilt. It sat for approximately 2 months before I took it back out.

[Murray]

Two months old fuel should be okay. You won’t damage your engine with a higher than normal oil/fuel ratio, just foul the plugs. Solarman has a good point with the idle air mixture, to my understanding a dirty/improperly tuned carb. will cause an engine to smoke excessively. Might explain why your engine shut down. Have you considered changing two cycle oil, the newer synthetic oils are suppose to burn cleaner. Are you the original owner? Reason I’m asking is, as the engine looses compression someone might have adjusted the carbs to regain power, you get the top end done and now your carbs. are out of adjustment. Just speculation.

[Oldham22]

I'm not the original owner, I have only had it for two years. I would assume that since this is the first tank of gas since engine rebuild that carbs are adjusted properly. I will look at the idle air mixture, plugs, synthetic oil, etc, I will also add some stabilizer and top off the tank to see if that helps. I'm no boat mechanic, so all of your suggestions are very helpful and appreciated!

[Murray]

Assume nothing! If you don’t already have a service manual I’d strongly suggest you get one. Genuine Suzuki Service Manual are pricey but they are your best bet. Suzuki didn’t make a 145 HP in 1998. See “Buy Suzuki Parts” tab at the top of the page

[Oldham22]

Typo, sorry. It's a 1998 DT140

[Solarman]

You said it was rebuilt? Hopefully properly. How far they went into the rebuild is questionable?

Yes, the oil injection system has to be considered when mixing to 50:1 ratio. The oil system is set for (between) 75:1 & 100:1, the manual would tell you for your year motor. This means your present mix is closer to 25:1, so you are running very rich in oil.

I would correct the oil mix before going any farther, mark the oil container on the motor, then run the motor some, the heavy smoke should clear up considerably. You will notice the motor runs much better, with the oil mixture closer to what it should be. After that tank runs through, refill with fuel and stabilizer only, IF the oil level in the tank shows it is using oil normally.

Don't change any mixture settings until you have a manual.

Good luck, post back if other questions.