Break-in fuel oil mix

[vvantassel]

Hello All.<br /><br />I know this is an old topic. Have searched the post's and realize the answer is most likely going to be 50:1. But here is my unique situation.<br /><br />I Purchased a used boat with a 1995 75hp (C75TLRT) Yamaha on it. The boat and engine run great.<br /><br />Not knowing anything about fuel oil mixing I asked the guy who sold it to me what he used. He said 8oz of oil to 6 gallons of gas which if my calculations are correct would be 100:1. He did not have the manual so I began searching the internet for information.<br /><br />A quick search of the internet reveals yamaha recommended using 100:1 mixtures for their smaller engines not too long ago. But, most of their 75hp models look like they should run at 50:1.<br /><br />The engine was recently rebuilt and I inherited it with it's final tank of "double oil" from the original owner to finish it's break-in. As best I can tell this his double mix was 16oz to 6 gallons which would be 50:1 not 25:1 as appears to be common and recommended by Yamaha.<br /><br />I've since run about 4 tanks of Pennzoil XLF synthetic which I got at Wal-Mart at what I now know to be 100:1 (8oz to 6 gallons) with no apparent problems. I've probubly run it a little rich as the tanks only hold about 5.5 gallons.<br /><br />Should I keep running at 100:1?<br />Is Pennsoil XLF synthetic OK to use on a rebuilt older engine?<br />Have I possibly already ruined or shortened the life of a newly rebuilt motor by running it to lean?

 

[moderator1]

Re: Break-in fuel oil mix

Welcome to iboats, vv.<br />I would highly recommend a manual for your particular engine. Not only will it answer your oil ratio question, it will be of good use in the future for other various questions you may have.

 

[rodbolt]

Re: Break-in fuel oil mix

hello<br /> switch to 50-1. most likly no damage has been done. I built an 88hp jonnyrude for a friend of mine. I mixed the first 6 gallons at 25/1 and told him to run two tanks then go to 50-1. he forgot. he mixed all subsequent tanks at 100-1. almost 2 years later he and the caretaker at beggars island hunt club had an argument on fuel mix so he called. that is when I found he was and had been running 100-1 for almost 2 years. caretaker was right. but the motor is still chugging and that was 4 years ago.

 

[JB]

Re: Break-in fuel oil mix

As far as I know most of the engine troubles related to using a 100:1 mix occurred while the engine was stored.<br /><br />Inadequate oil coating on ferrous parts (crank and rod bearings, cylinder sleeves) allowed rust to form with subsequent catastrophic failures.<br /><br />That is why OMC, at least, changed all of their 100:1 recommendations to 50:1.<br /><br />I agree with Rodbolt and moderator 1. Get a manual and switch to 50:1.<br /><br />Good luck.

 

[vvantassel]

Re: Break-in fuel oil mix

Thanks everyone. What a great forum for newbies to boating such as me.<br /><br />I've just ordered the manual per the moderator's suggestion above. Yamaha sells them on their web site for $30. <br /><br />If you are interested, follow this link then go to the parts & service pull down. next, click on view manuals. You can then enter the year, product line, and model of the engine manual you would like to see. If it's later than 1998 you don't have to spend the money to buy the hard copy.<br /><br /> http://www.yamaha-motor.com/products/categories02/5/otb/yamaha_outboard_motors.aspx <br /><br />I was using the 1998 C75 manual as a reference thinking motors have not changed that significantly over three years. That's where I saw the 50:1 mixture rating vs. the 100:1 told to me by the previous owner. <br /><br />Rodbolt and JB...thanks a lot for putting my mind to rest on this subject. One thing I did not mention; just to be safe I had a local mechanic take a look at the motor before I put my family on the water. He recommended replacing the water pump propeller since it had not been done as part of the rebuild. I did and though I did not think it was possible the flow increased considerably. At least the motor is getting a good cooling flush while running.

 

[31900]

Re: Break-in fuel oil mix

Replace that impeller at least every 2 years. About the fuel mix, Yamaha tells me 100:1, others 50:1. I go for the middle, 75:1. Works great for me.