100:1 ratio

[rojac]

Thanks for all the feed back, a decision has been made, put a deposit on a DT30 suzi ls tiller electric/zip start made in japan motor. 2 years recreation use warranty for $3300 only 10% more than the non electric start that I've been quoted on. Also runs 100:1 but dealer has recomended 50:1. Suppose the mix would come down to how long are you going to keep the boat.

Next boat and trailer

cheers

rojac

[Owen]

Just a bit of food for thought.
100:1 is probably driven mainly by environmental factors, however less oil = more horsepower.
Also as most motors are now injected, there is less chance of seizures from things like running out of fuel.
As for the wearing out of the motor not being of concern to the manufacturers, well the most dangerous period for a motor is when it is new. Everything is tight. SUrface imperfections have not yet worn off etc etc.
If the manufacturers thought 100:1 was in the danger zone, then they wouldn't recommend it for fear of seizures DURING the warranty period.
This is why they commonly recomend adding oil to the fuel even on injected motors during this period.
I'd be more converned about using a quality oil that supplies the required lubrication at the factory recommended level than dumping more oil in just because some mechanic thinks it may be better to run twice as much oil.
If for no other reason than it's the right thing to do for the environment.
Can't believe I said that

cheers,
Owen

[winston]

Hello Rojak,
I have a CV30 Yamaha and run it at the recommended ratio of 100:1. it runs a little too rich on idle jet as it does foul the plugs after 5 minutes of trolling. The motor is four months old. I was hoping to run it this weeked and lean the idle a little.My point is even 100:1 is plenty of oil. I had a CV 40 for six years and also ran at the recommended 100:1 ratio, I did approximatley 350 hours . The head was remoned after five years and the mechanic said it still looked new. I am not a mechanic but trust the advice of Yamaha's world class engineers and designers. If they recommend 100:1 then this is best. Cheers Winston.

[Bowser]

Well I have run my 30hp 3 cylinder Yammie on 100:1 for most of the time I have had it. Of late I have bumped this up a bit because I have increased the weight and load on the motor and it is working a little harder and at higher revs. Originally the boat was a tiller steer and rarly did I get above half twist on the throtle. At this it was plenty fast enough for me. I have also always used Yammie lube and haven't had any sign of problems as yet.

Bear in mind that with fuel injected models the motor at times is running at 200:1 ratio. There are a lot of comments here that 50:1 is proven ratio, and it is on old motors. These do not have the technology of current motors and they are a bit like comparing an old holden red motor to the current crop of engines. The manufacrurer recomends the operation at 100:1 and they sell it into the US at that. Do you honestly believe they would do this in the litigation mad US if they felt that it was going to damage the motor at any time? If they did some yank would have them taken to the cleaners over it somewhere down the track, either alone or in a group action and US courts tend to pay out big time.

[billfisher]

Owen,

I don't quite understand your reasoning. I agree that the run in period is critical, but this is why the manufacturers stipulate a 25:1 ratio for the first ten hours, and 100:1 thereafter (or 50:1 in the case of Tohatsu).

Bowser, so what is different about the current crop of motors that makes them run on 100:1? And why does Tohatsu recommend 50:1. As far as I know Tohatsu has the same design with needle bearings.

[Owen]

Billfisher,
Don't feel bad about not understanding my reasoning. I just re-read it and neither do I.
The point that I so clumsily tried to make was that the run-in period sets the standard for the life of the motor. Done incorrectly (regardless of oil/fuel ratio) the life of the motor and the wear rate suffer.

I'm not sure if Yamaha (the engine in question) actually does specify a higher oil/fuel ration during run-in. I did a search and can't find anything sayings so although other brands do.
However regardless of whether they do or don't, they wouldn't recommend 100:1 if it wasn't safe. The run-in is only a few hours. The warranty period is two or more years.
Engineers in this litigious (sp?) age tend to err on the safe side. They know joe public is just going to fill it up with fuel and go.

Newer engines are in fact quite different to older two strokes. Bore coating and ring technology have come a long way. So have quality oils.
The recomended ratio will have taken into account the properties of all of these factors. i.e I wouldn't do it on my Mercury, because at it's age I'm sure it has cast iron bores and chrome rings at best. We used to do it back in the 80's with our race bikes (using synthetic oils), but motor life wasn't of prime importance - horsepower was.

I would personally run more oil during run-in, but I'd be quite happy going 100:1 after that.


cheers,
Owen

[Mr__Bean]

The only time I would increase the oil would be if I felt my use of the motor was placing it under fairly constant high load conditions.

If your use of the engine is mainly low load applications, putting around with lures out, running around at part throttle, then I wouldn't contemplate more oil than the recommendation.

If however your motor is constantly run under a heavy load, then I would consider dropping back to 50 or 75 to one, based on your particular harsh operating conditions.

Additional oil at low speed/low load may end up doing more damage than good if you coke it up.

- Darren

[MyEscape]

Owen,

Just a point on the run-in for a 30hp Yamaha. I recently purchased one (a 30hpCV Yamaha), the dealer's advice was the first 2 tankfulls of fuel at 25:1 then thereafter at 100:1.

Beleive me 2 tankfulls (at 24 litres per tank = 48 litres through a little 30hp = quite a few hours of running) is a fairly good run-in period.

After that 100:1, and also because on a 4.15m tinny it's not working so hard(note Mr Bean's comment about working hard), would seem fine following the manufacturer's advice.

Steve

[billfisher]

So far no one can tell me why Tohatsu has a 50:1 ratio. I don't think they are behind the others in engine design.
The load the engine is under is an important consideration. As I drive around near full throttle most of the time I am more happy with a 50:1 ratio.
Obviously 100:1 will not rapidly destroy you engine, but it will (so I have been told) lead to more wear and shorter engine life. This will only manifest itself when the engine hours get high. No one will have any comeback with the manufacturer when their motor gives up after 8 or 10 years even in litigious US. The main worry over there for outboard makers is environmental concerns and this is why they have gone for 100:1.

[Owen]

Steve,
Was the 25:1 thing just the dealers advice?
Or was it factory mandated? i.e. Written in your owners manual.

Billfisher,
I don't really have an arguement that can be applied broadly against what you have said. In fact I'm not really trying to argue anything at all - just offering a different view I suppose.

However 100:1 will only reduce engine life if the oil in question does not produce adequate lubrication at that ratio. Any extra after that does nothing more than contribute to environmental concerns and wasteage. I can see your point regarding comeback on the manufacturer after many years of service, but on the other hand it would be commercial suicide to design an engine that in the eyes of the consumer had a limited service life. Engine manufacturers would be planning to be around selling engines longer than that IMHO.
If your motor says use 50:1 than do so. Mine does, and I do so. It May well be fine with less oil, but I'm not about to experiment or second guess the designer.
I just find it odd that fisho's claim to be friends of the environment on one hand and then on the other hand, think nothing of adding extra oil to our waterways for no other reason than the logic that if some is good, more must be better (unburnt oil is exhausted into the water).

cheers,
Owen

[billfisher]

Owen,

A premix motor will always waste some oil because you are stuck with a single ratio which has got to cover from idle to full throttle, ie the premix ratio is a compromise. Nearly all the larger (hence potentially more polluting) motors have variable oil ratios which only add the extra oil when its really needed, hence the ratio can vary from 50:1 to 200:1 according to the revs.

[rojac]

But how many engine hours are we talking about, 8-10 years for the motor, have to weight up if following manufacturers specs is going to seriously reduce the longevity of the motor given that its overall cost is not that great.

Would the quality of the oil ie synthetic make much difference ( they say it all comes out of the same tank )

cheers

rojac

[stunnedmullet]

Gidday Rojac
I purchased a 30hp cv yammy last year and although the manual states 100:1 , due to the high humidity and extreme conditions in Nth Qld it was recommended to run it on 50:1 My outboard mechanic(not associated with the dealer) agreed this was okay.
Initially I was told to run 2 tanks of 25:1 in it and then 50:1 after that. I have had no problem running a 4.2 m quintrex explorer with a full crew.
A cv 30hp yammy will idle rough at continuos low speeds because that is there nature. If you want something that runs smooth at idle for long periods then buy a 3cyl trible carby or a 4 stroke. Horse for courses. Should only be using TCW-3 rated oil for any premix outboard by the way. That is in any manual.
Good Luck with your purchase.
Damo

[billfisher]

The extra oil is a big plus when the motor is used infrequently too. You have twice as much left coating the cylinders and pistons with the 50:1 ratio.

[MyEscape]

Owen,

The handbook for the 30hp CV Yamaha states 25:1 for the first 10 hours, 100:1 thereafter.

Stated the same by the dealer, Reef Marine in Mackay, albeit more simply as first 2 tank fulls of fuel. Probably as a 30hp doesn't have an hour meter.



Steve