Basics for new-to-me 4-cycle Yamaha F90

[Seahawk170]

I recently purchased a 2013 Yamaha F90 4-stroke outboard, so this in my first 4-cycle outboard and have some basic questions.
(WARNING--OIL THREAD QUESTIONS) Sorry, but my search here was unsuccessful, or the question below would never be asked!!

My owners manual specifies 10W-30 engine oil (that meets req'd specs),but I was wondering if synthetic is completely safe to use in it, AND if the type of oil absolutely needs to be Yamaha specific brand for best results?

Is a high quality synthetic hypoid gear lube better in my gear case than conventional dyno-oil? (always wondered about use of this in a 2-cycle's lower unit as well)

I'm not new to working on motors, and always serviced/modified all the various motorcycles I've owned over the years, and was a firm believer in synthetics for my bike's engine & gear box, but was curious about it's successful use with outboards for thermal benefits.
Personally I know that some engines run quieter with X-Brand oil, and my neighbor's 'Buit' Harley prefer dyno oil, so just thought I'd ask for recommendations from the Pro's here, before I risk any issues with my recently acquired Yamaha outboard.

Thanks, and again I'm sorry for starting this slick subject.

 

[flyingscott]

Yes you can use marine rated synthetics in your motor does not need to be Yamaha specific. Yes you can use synthetic in the lower unit also needs to be marine rated. Really no difference between 2 and 4 strk lower units. I don't know about thermal benefits. I think that would be more of a thing with an air cooled motor as opposed to a liquid cooled which your motor is. As far as running quieter I think it would depend on the motor. Your neighbors Harley is air cooled so built with larger tolerances to compensate for the temperature range it will run in. The outboard has a thermostatically controlled cooling system allowing for more stable temps and tighter tolerances. Plus the Yamaha is really a nice engine built extremely well one of the best out there maybe the best take care of it and it will last forever.

 

[tommarvin]

Good for you, We use 100% synthetic everything. Marine gear lube is tested with 10% water contamination easily passes.
Two cycle oil burns so clean never any carbon buildup. Never have to decarb.
Get the right marine grade motor oil, lots of choices.
I'm guessing you paid at least 10 grand for your 2013 F 90, It's amazing how many people go into " CHEAP OUT " mode after they buy an expensive motor!
If you have EFI/fuel injectors, there is diagnostic software for just 65 bucks on e-bay to diagnose all problems and log maintance, cables included. You need a laptop or tablet to look at it. Do the maintance it's so easy and fast cheap, flush it if you go in Puget sound, The motor will never break and outlive you.

 

[Seahawk170]

Yes you can use marine rated synthetics in your motor does not need to be Yamaha specific. Yes you can use synthetic in the lower unit also needs to be marine rated. Really no difference between 2 and 4 strk lower units. I don't know about thermal benefits. I think that would be more of a thing with an air cooled motor as opposed to a liquid cooled which your motor is. As far as running quieter I think it would depend on the motor. Your neighbors Harley is air cooled so built with larger tolerances to compensate for the temperature range it will run in. The outboard has a thermostatically controlled cooling system allowing for more stable temps and tighter tolerances. Plus the Yamaha is really a nice engine built extremely well one of the best out there maybe the best take care of it and it will last forever.

Thanks for the reply and easing mind on this subject. I suspected the lower units would be the same but had to ask just in case. As for the thermal benefits of synthetic, I know it handles more heat so hopefully it'll help some if the water intake gets covered by a bag that some senseless person has discarded. A service manual will be ordered soon, as I plan on doing all my own maintenance on this motor.. except for sensor issues, since I hate dealing with that. LOL

 

[Seahawk170]

Good for you, We use 100% synthetic everything. Marine gear lube is tested with 10% water contamination easily passes.
Two cycle oil burns so clean never any carbon buildup. Never have to decarb.
Get the right marine grade motor oil, lots of choices.
I'm guessing you paid at least 10 grand for your 2013 F 90, It's amazing how many people go into " CHEAP OUT " mode after they buy an expensive motor!
If you have EFI/fuel injectors, there is diagnostic software for just 65 bucks on e-bay to diagnose all problems and log maintance, cables included. You need a laptop or tablet to look at it. Do the maintance it's so easy and fast cheap, flush it if you go in Puget sound, The motor will never break and outlive you.

Thanks Tom for the confirmation. The marine mechanic I spoke with believes that the ring-free product was beneficial due to the additives in gas; he said that he could definitely tell on his customer's engines that used it, versus those that didn't. My 2013 F90 was a lease return engine, but always dealer maintained and mostly trolling hours on it, and your estimate is about double, but I still do want this to last me for many years. Thanks for the tip on the diagnostic software, I'll definitely have to order that up. Every time out I'm a firm believer in flushing, plus I already have the recommended additive & hose adaptor to remove most salt in it's passages. Thanks again for all the beneficial information and suggestions!!

 

[99yam40]

I have read the Yamaha does not recommend synthetic in some lower units,
If there are any bushings in the lower unit not to use it

 

[flyingscott]

If you are using the synthetic to try and save your motor from a water pump failure or overheating that won't happen. Another problem with synthetic is if you put it in a motor with hrs on it there is a potential for it to leak and no oil will save your motor from an overheat here's why. Do not think of this like a car or bike motor because at cruising speeds a car is usually around 500- 2000 rpm so if it overheats not the worst. A boat engine on the other hand will run between 500 to 6000+ rpm so if it overheats at speed it's bad. The most important thing is to get the right rated oil for your motor which is in the owners manual. No such thing as cheaping out on oil if you get the right oil they all need to meet the same specs synthetic or not. If you really want to save your motor replace the water pump regularly and read your owners manual has all the info you need.

 

[Seahawk170]

99yam40, thanks I will verify with my local dealer first. A bushing is an odd reason for not using synthetic though, My current Harley and my previous Harley engines were able to safely run synthetic, and both engines had some bushings in them, but definitely will verify first.


flyingscott, thanks for the input. Sorry, but I disagree with your comparison with motorcycles though, since sportbikes are regularly ridden in the 5,000 to 10,000 rpm range, and are mainly water & oil cooled. The synthetics being more slippery/viscous is an old myth.. if a seal or gasket is bad it simply needs to be replaced. I definitely will not cheap-out an an engine's life blood, and mine are always changed ahead of schedule and with quality stuff. I fully agree with you about maintaining and replacing the water pump regularly, plus any other scheduled replacements per the owners manual. Thanks again and safe boating.

 

[flyingscott]

Bikes have it easy 6 speed transmissions narrow power bands they really don't have to work hard at all. Bikes also only have 2 wheels not a lot of resistance. A boat motor on the other hand has to have enough power to start the boat out loaded sometimes with a skier or tube sometimes more than one. Then needs to have enough power to push the boat on plane. And do it with all my fat friends in the boat. Put that bike motor on a lower unit once see what happens. Comparing an out board motor to a bike is like comparing rotten apple to a skunk the only thing they have in common is they smell. The synthetics do have the leak problem because Amsoil sells seal conditioner to be specifically used before you put synthetic in. I don't know what sport bike you have but my 2016 NINJA runs to 11000 RPM. My question to you is synthetics being more slippery/Viscous is a myth why bother using them that was always there main advantage.

 

[Seahawk170]

hmmm, my current bike is a 2014 Harley Dyna with a windshield,and all except (1-bmw) were cruiser bikes (max 6000 rpm). The 'biggest' resistence is wind, since a cruiser bike has the drag coefficeient of a brick. I've toured through all the southwestern states on several of the cruiser bikes I've owned, and a strong headwind or high mountain hills definitely puts a big load on the engine of these 725# to over 800# bikes, Your new Ninja is aerodynamic for racing and puts out a ton of power for it's weight, so regardless of the rpm's you run I doubt you'd notice much load unless you were to tow a broke down HD. LOL
Granted, an outboard engine is always under load (never coasting), but the propellor definitely acts like a transmission to slowly deliver it's prop-slipping power to push along the wetted area of the hull. My goal is to rarely ever run my F90 above 4200 rpm's, and keep it's inners lubricated with a good quality oil.

Sorry, I really hate to argue but would also like to mention that there are many seal conditioner products sold for all oils, and agree with your previous post for use in worn out engines. There are those that absolutely HATE synthetics, and will only use Dyno oil, and nobody will ever change their mind. Don't care, and respect their oil choices. Personally I really like synthetics for it's much higher thermal break-down quality (lasts longer between oil change), and I change earlier than required for peace of mind. Since you mentioned that an outboard is subjected to more stress than cars or bikes, then all the more reason for using synthetics. ;-)
As we all know the most important thing about maintaining an engine is keeping it clean with good and frequent oil changes.

 

[tommarvin]

Motors last longer, and you know it, because less friction and wear plenty of data to prove it,no carbon, petro has carbon,no dry starts for two months, low smoke, the only way to get away from smoke on a two stroke, wait for it WOT,low stink, petro stinks, cleaner for the environment low aquatic toxicity tested petro nasty dude it's just not good, it cost less that's why almost everybody use's it's ok, some people don't buy the cheapest thing, all the time, and CHEAP OUT. The few people in the know buy the best stuff, they don't think about money,they own the boat, the boat doesn't own them. You asked a question, I replied to your question,peace

 

[flyingscott]

Don't be afraid to run your motor to it's max RPM they are designed to handle it. Don't be afraid to let it go babying them will not increase there life expectancy.
I never said synthetic was bad just said there was things to watch out for on a motor that has some hrs on it. Tom you bring a smile to my face with what you said. Most of my motors were built before 1970 according to you they should all be dead because I did not run synthetic in them. Show me one realistic test about lake toxicity outboard motors have been around over 100yrs and according to you all lakes that run outboard motors should be cesspools from the toxicity of the cheap people not buying the right oil. I will tell you something else synthetics do not make a difference in an oil injected motor because most of them cannot adjust how much is injected so it's the same amount and that's why there is injector oil and premix oil. Another thing you are wrong about going up hills on your bike and it's struggling you can shift down find an easier gear. An outboard has to overcome aerodynamic and hydrodynamic drag with nothing but brute force. And if you think that prop is slipping try this,put your boat in the boat landing leave it on the trailer and hammer on it and see how many RPMs you pull. But I have to go now because it's cold out side and my boat wants some hot chocolate and my motors want to be tucked in cause they own me. One more question If you have no carbon in your motor what kind of fuel are you running.

 

[Seahawk170]

Tom, thanks for the perspective, and I'm sorry for causing a commotion over this sensitive subject.

Scott, thanks for easing my mind about running it wide open, as I suspect that since the Yammie's & Honda's have designed engines for a long time now to handle very high RPM's, and that these outboard engines are very conservatively rated at 6,000 revs as a freewheel safety margin.
I will take all you said seriously, and then draw my own conclusion for my engine's oil and we'll quietly leave it at that. ;-)

My first thought when posting this question was worrying about causing arguements and people turning against each other, so I'm sorry if this sensitve subject has caused any bad feelings. I've decided now to just visit my local marine dealer for their suggested oil in my F90, and just go with their recommendation..good or bad. LOL.

 

[flyingscott]

There is no commotion at all everybody has an opinion it's your motor and your money so in the end your decision. I just gave you my opinion on things I have seen happen to peoples motors. No harm no foul

 

[Seahawk170]

Thanks Scott, I will definitely inform the marine supply dealer of my engine's hours as you suggested, just in case.
Thanks for the 'head's-up' on this matter.