Synthetic oil 3rd yr Yamaha 4 stroke

[Fishstix]

A few years back I switched my 115 Yamaha to synthetic motor oil.

The reason I did it is at 100hrs.the regular oil appeared to be beatup and drained out like water. Yamaha does not recomend synthetic in their engines.

Well so far [3yrs] so good the engine runs quieter ,seems to burn less fuel.(dont know for sure} and at 100 hrs when I drain the oil it still looks like oil.

Last yr I added a new Yamaha HT8 kicker put about 400hrs on it. I started this motor out with synthetic oil, Ive changed it 4 times and it

drains out almost like "new oil".

I want everyone to know Yamaha DOES NOT RECOMEND synthetic motor oil. But Ive got to say it works for me. I use synthetic gear oil in my truck transmissions and rears . Since I switched no tranny or rear problems. And my stuff gets abused.{log trucks}

The reason behind this post is I agonized a long time before switching to synthetic. The stuffs expensive and so are boat motors.But I think its worth it. No Im not a oil salesmen. But it is the time of year to think about your motor oil. reducing friction = better milege.

I do not use synthetic in my p/up or car but if gas keeps going up Im going to give it a try.Probably shortly. Im hearing 4bucks a gallon by summer.

[jimski2]

I think most engine manufacturers want regular oil used is to seat the rings in the cylinders better. Some engines increase their mileage after a couple thousand miles when the rings wear into the cylinders. A friend of mine used synthetic oil in his new Ford and that car burned oil forever. Ford blamed it on the synthetic oil as it is too good and the rings never "wore in". But today Ford wants you to use their 5W20 oil to increase the corporate average fuel economy.

[Gill-T]

When I put my new block in my 305 I/O, I used regular oil for the break in season. I have since used synthetic and have found the same thing....the oil looks as clean as the day it was put in! My plan to save money on oil is to drain one quart out at the start of the season and replace with one new quart before start up. My thinking is compared to a car....we don't put the miles or time on our oil with our boats each year....so why change it if is not needed? By adding one quart to the upper engine compartment before start up I may be protecting the upper engine when the key is first turned in the spring. I am also running the synthetic in my trolling motor. No problems reported.

[Misty IV]

Since we're on the topic of motor oils, I have a question for those of you with Mercruiser engines. My engine specs say I have to run a special 25W-50 motor oil that only is available as a Mercury item. No other motor oil manufacturers offer this special grade. This oil isn't cheap either. Granted, I usually only change the oil once or twice a season depending on the hours, but can I do any damage by using, say, a 20W-50 from a major oil manufacturer, like Pennzoil, Quaker State, Mobil, etc.? What about using a 10W-30 grade? I can get bulk oil in cases through work, and if I can use what I put in my truck in the boat, makes life easier. Any input on this subject? Thanks!

[Diversion]

The reason you are supposed to use 25W-40 Mercruiser oil in an I/O is that an I/O runs hard, its not like a car with a transmission where it shifts and the load is reduced through a gear reduction. The heavy oil keeps the motor properly lubed under stressful loads, such as when on plane. If you were to run 10W-30 in an I/O, you would experience a lot of lifter noise at higher RPM, at that point, the motor is at a higher stress rate and the oil just won't stand up to the pressure.

When I had my boat in the shop this summer, my mechanic asked me what type of oil I ran, I said 25W-40 Mercruiser oil, his reply was great, don't run anything less.

I guess it all comes down to spending a little more $$ now on maintenance, or a lot later.

[Misty IV]

The reason you are supposed to use 25W-40 Mercruiser oil in an I/O is that an I/O runs hard, its not like a car with a transmission where it shifts and the load is reduced through a gear reduction. The heavy oil keeps the motor properly lubed under stressful loads, such as when on plane. If you were to run 10W-30 in an I/O, you would experience a lot of lifter noise at higher RPM, at that point, the motor is at a higher stress rate and the oil just won't stand up to the pressure.

When I had my boat in the shop this summer, my mechanic asked me what type of oil I ran, I said 25W-40 Mercruiser oil, his reply was great, don't run anything less.

I guess it all comes down to spending a little more $$ now on maintenance, or a lot later.

Thanks for the info, Adam. Explains a lot and I appreciate the detailed explanation. Answered my question. I'll stick with the Mercruiser-spec oil. The additional cost of the oil is worth it to keep my engine running the way it's supposed to for a long time. I'll leave the 10W-30 to my truck's engine. Thanks again!

[goingagain2]

think about where your motor is ... its covered in a cramped space, keeps a lot of heat in there, and like was said it works hard. when i return to port i open my doors to engin room to exchange heated air. been using 20/50 for 15 yrs, no prob. 350 lt chev. (no trolling)

john

[muskybob]

been using 20/50 for 15 yrs, no prob. 350 lt chev. (no trolling)

john

WOW, a 350 litre engine? You must pilot the Queen Elizabeth.