How much oil is consumed...

[scooper77515]

On the 787 (96 XP), I have run it maybe 20-30 hours, and have seen little, if any, oil consumption. I am wondering if my oiling system isn't working up to par, and if I should start to add a little oil to my gas. Not the full mixture amount, but maybe half-strength...

Other than a little smoke, would it hurt to add some to the gas?

Or is it normal to see very little drop in the oil tank over this short amount of time?

 

[Dennis]

Oil Consumption

Average oil consumption should be about 1 gal. of oil to 45 gal. of gas.
DAWG

 

[scooper77515]

Hmmm...

I have put in about 25 gallons of gas, and no oil. The reservoir still shows it being full, or darned close to it. I may have put maybe a pint in there to top it off when I bought the gallon of oil...

Should I start adding some to the gas?

Makes me wonder if this is part the reason for last week's seize up...

BUT!!! The cylinders look really good, still have good crosshatching, so it seems like THEY are getting lubed enough.

 

[seadoosnipe]

Injection oil!....

Scooper, I fill up my oil tank once a season with 1 gallon of synthetic oil. I see where DAWG says about 45 gallons......well, if that's true, I'd be running a littlel lean too!....
But I just pulled my heads to replace the top cap, the pistons were beautiful. So, I think my usage is o.k....
Scooper, take a Sharpie and make a little mark on the clear, large tube going to the rotary, ride for a few days, then check your mark. Make sure, you check it in the same position and place where you marked it, so the reference is a good one.
If your worried about it though, it won't hurt to put a little extra in. It will probably smoke a little and if you put in too much, you'll foul plugs, but it won't hurt the engine.............

 

[Dennis]

Oil Ratio

Hi everyone,
Don't know if I"m ready for another debate but the way I see it is this:
50 gal fuel/ 1gal oil = 50 to 1 ratio
45 gal fuel/ 1gal oil = 45 to 1 ratio
40 gal etc, etc
THANKS, DAWG

 

[seadoosnipe]

Fuel ratio....

Dawg, I like that answer.......very good point in fuel consumption. But that's not necessarily how the system works.
When Sea-Doo users switch to pre-mix, then your equation is correct. But for those that still use the oil injection, that point is mute. Here's the reason.

The Rotax oil injection system, variable oil injection pump, speeds up and slows down. You need less oil added to the fuel at slower speeds than you do at higher speeds. This is where the term "varaible" comes in.
If you do a bench test, you'll see the different measurements in the different eninges. In theory, on a 50:1 fuel/oil ratio, with the same amount of fuel in each, the 717, 787, and the 947, would use that fuel and oil in the same quantity. But if you look in the manual and preform the bench test, the 717 needs 1.5 mls (milliters) at 1500 rpm for 30 seconds. The 787 .75 mls and the 947 at 1.01 mls. So just in this test, it shows how the variable rate oil injection pump distributes oil in difference to pre-mix.

But you do have a point....if you pre-mix, then your calculations are correct. That's why I like my injection system. It uses less oil which in turn, builds less carbon deposits in my engine. This I have seen personally in engines running premix. You see, pre-mix is a safeguard in oil requirements. It's not necessary to run a constant mix ratio of 50:1.....it's just impossible to variate that inside a fuel tank. :cheers:

 

[kustomkarl]

To add my comments to what's been said already, I would check the plugs and look for a small amount of smoke out the exhaust, while running. The plug reading is a very accurate way to see it it is too lean or rich. What Dawg says make great since as an average usage of oil. I use it to to determine if consumption is high or low in my own 2 stroke machines.

 

[robin savell lloyd]

I see all your points and they all seem to have some credibility. the way I see this may be wrong so please correct me if it is. I would not think that this seadoo would have any less oil at idle than a mixture of 100 to 1 that is geting preaty thin on oil but i do supose they may even require less at idle. but any way if you idel all day long tel you burnt up all 25 gallons of gas the way I would see it you would use one quart not one pint of oil and this is at idle and your oil injection pump is delivering oil at 100 to 1 this is only a guess not a test.

 

[seadoosnipe]

Oil use....

The Rotax oil injection system, variable oil injection pump, speeds up and slows down. You need less oil added to the fuel at slower speeds than you do at higher speeds. This is where the term "varaible" comes in.
If you do a bench test, you'll see the different measurements in the different eninges. In theory, on a 50:1 fuel/oil ratio, with the same amount of fuel in each, the 717, 787, and the 947, would use that fuel and oil in the same quantity. But if you look in the manual and preform the bench test, the 717 needs 1.5 mls (milliters) at 1500 rpm for 30 seconds. The 787 .75 mls and the 947 at 1.01 mls. So just in this test, it shows how the variable rate oil injection pump distributes oil in difference to pre-mix.

Robin, in a variable rate oil injection system, the amount of oil needed to lubricate the engine varies with the speed of the engine and the size/type. That is why you'll see the difference in oil flow rates at 1500 rpm for 30 seconds in each of the above engines. These engines can be found in the same hull designs with the same fuel and oil tanks but consume their oils in different quantities. So the idea of oil/fuel ratio in the Rotax variable rate injected engines being used the same is, by the shop manuals, just not so. The only reason oil is mixed or injected is for lubrication of the engines components and each of the Rotax engines have different oil requirements.
When asked about pre-mix, you'll get the answer or either 50:1 or 40:1. That is because, with-out a way to variate the amount of oil that is "required" for the engine, we over mix to ensure the engine runs as smoothly, with the least amount of friction and the oils capability of removing that heat/friction without fouling the spark plugs.

 

[robin savell lloyd]

I do see the point but even that method will have a ratio at idle and I would like to know what that number would be. when I find it that it will help me to understand consuption in a easy way. the book tells you how many ml of oil in 30 second if it would tell us the the amount of gas it uses in the same time we could do the math. I think

 

[kustomkarl]

The amount of fuel used in a 30 second time period would be useless as it isn't the amount of time but the amount of lubrication needed. At higher Rpm is a heat factor and a flow of fuel that requires a specific amount of lubrication. Heat is the factor that requires more lubrication from friction. Engines aren't rocket science and lubrication isn't perfect because wear and tear is always gonna be present. Oil just allows longer use and reduces friction and in turn reduces quicker wear and tear. Higher rpm's = more heat and friction, so variable injection means less consumption and less over oiling, which leads to longer life, and less chance of fouled plugs....Oil consumption is all relative to rpm's and heat/ friction. Does that make any better sense now? I hope it doesn't confuse you any further.

Karl

 

[seadoosnipe]

Oh....

Oh.....I see your point now. That is a different way to approach it. Say at idle, the 717 burns the least amount of fuel in an hour, so the oil ratio should be lower..........
I think I see what your saying. I'll have to look at that because I know in the tech data in the back of the manual, they give the amount of fuel used per hour and how long it takes to burn it at WOT....so maybe, with a little algabra, I can come up with an answer.
This may take a little while...........My brain doesn't do calculating that well........:ack::rofl:
I'm more like Jethro Boudine.........I got to cipher.

 

[kustomkarl]

Louis, The WOT consumption doesn't have the most valuable factor nor could it in calculating the 100% consumption factor. Tempature...because the engines are in a body of water that would vary a lot from Florida to Canada The WOT idea, is to generalize the consumption at a general temp I believe at 65* as is all fuel to have the correct analogy of it's volume. Does that sound correct to you ?

 

[seadoosnipe]

Shop manuals....

It does sound logical....man, that was weird.....I came in to answer a post and now, when I come back, that spot has already got an answer....man, that's the hebejeebies....:ack:
I didn't quote the exact results in the test, I took an average. Because of that reason. But I didnt' think this discussion would go that deep.
But all this information is in the technical data specs of the shop manuals. Anyone can do the math. I believe that it was meant as a way to make sure you had the minimal requriements..........that's all.
BTW Karl, I think you mis-read something to post your statement in post 11. The idea of measurement was taken from the shop manual to test the amount of oil from the injection pump to ensure that it was delivering the necessary amount of oil for lubrication......

 

[kustomkarl]

Louis, I was making a general statement in post 11, not a calculation of measurement from a manual, on oil pump measurement...just an observation of the general factors of lubrication, based on friction and temperature.

 

[Dennis]

Oil Ratio

Hi Everyone,
I think what SEADOOSNIPE is saying is that with the variable ratio oil pump there is no set ratio of oil/fuel. (nominal figures) The injection pump may only supply a 80to1 ratio when the engine is at low rpm but may supply 40to1 ratio when at high rpm. The design of the injection pump fine tunes the fuel/oil ratio and therefore less oil is used unnecessarily.
I disagree with the comparison of different engine injection pump flow numbers as a way of explaining this. You can't compare the 717 to the 787 or the 951 because the 717 uses mineral oil and the 787 and 951 use synthetic. The oil injection rate of the 951 is bound to be higher than the 787 because it is a bigger engine that has higher fuel consumption.
As far as my original statement of 1 gal of oil to 45 gal of fuel being a AVERAGE consumption of oil.......I stand by that. I've been around and worked on alot of stock skis' that have carb 787 and carb 951 engines and that have the factory oil injection system and owned by average riders and that, on average, is what they use. Yes, I'm using the "operation in practice" method to come to this conclusion. If the owner of one of these skis' told me he was only using 1/2 gal of oil to 45 gal of fuel there would be absolutely, positively no doubt in my mind that they had a oil injection problem.

Thanks, DAWG

 

[kustomkarl]

Uh...oh this sounds like a heavy debate again....:ack: :rofl: I better get some more beer...it's gonna be a long night!:cheers:

 

[robin savell lloyd]

Hi Everyone,
I think what SEADOOSNIPE is saying is that with the variable ratio oil pump there is no set ratio of oil/fuel. (nominal figures) The injection pump may only supply a 80to1 ratio when the engine is at low rpm but may supply 40to1 ratio when at high rpm. The design of the injection pump fine tunes the fuel/oil ratio and therefore less oil is used unnecessarily.
I disagree with the comparison of different engine injection pump flow numbers as a way of explaining this. You can't compare the 717 to the 787 or the 951 because the 717 uses mineral oil and the 787 and 951 use synthetic. The oil injection rate of the 951 is bound to be higher than the 787 because it is a bigger engine that has higher fuel consumption.
As far as my original statement of 1 gal of oil to 45 gal of fuel being a AVERAGE consumption of oil.......I stand by that. I've been around and worked on alot of stock skis' that have carb 787 and carb 951 engines and that have the factory oil injection system and owned by average riders and that, on average, is what they use. Yes, I'm using the "operation in practice" method to come to this conclusion. If the owner of one of these skis' told me he was only using 1/2 gal of oil to 45 gal of fuel there would be absolutely, positively no doubt in my mind that they had a oil injection problem.

Thanks, DAWG

you go dennis I hope you are right I just did a search and found another very respected mechanic who quoted all most the same thing. very, very close to the same numbers, your numbers were a litle richer but I like richer.

 

[ScubaDoo]

Dawg, your numbers make sense because of the different engines in size and recommended oil will vary and the pump must be configured as such to accommodate them. The ratio as much as 80 : 1 seems to me to be a little much, but I don't have figures at my grasp to prove different. At any rate the variable rate injector is a major accomplishment in the 2 cycle industry.

Yea, your right Kustomkarl...it's gonna be a long night...better buy more beer.
ScubaDoo

 

[seadoosnipe]

Time to do some polishing.....

O.K........seems like my writing skills are beginning to falter. I'm very well aware of the engine size differences and to what you've said, is pure truth. As to what I said, which for some reason (which I'll take fault for due to the way it was written) was taken totally out of context and obviously for granted. I guess I didn't expect this to become a huge debate.
Dawg, when you made the first about ratio in comparison to 50 gallons of gas to 1 gallon of oil, I compared that to my own, personal use in my 787. I have the 2 gallon capacity oil tank and use the Synthetic, low ash oil. Although, I don't know exactly how much fuel I've gone through, I have about half (a gallon) of that oil left from last year.
At the moment, my heads are off as is my carbs and exhaust. The inside looks fantastic. No signs of low oil use or lack of oil from my injection pump. That being said, I looked into the manual, 2003 I believe, to see what the volumes were to the test on the oil pump. The numbers I quoted in that post came directly out of the shop manual and were meant to reference that there are different volumes needed for the different engines. That there was also a difference in how those variable rate injection pumps were too, different.
That was in reference to the idea that pre-mix is 50:1 or 40:1, that all engines burn that ratio the same. And like you said, they don't. That was the end of it for what I was looking to say.
Although the 717, 787 and 947 all have some things in common, they are completly different engines. Their fuel and oil consumption is completly different. That was never in question.
But in trying to explain the idea that the Rotax isn't the standard 2-cycle engine and that the oil requirements vary from, like stated by you I believe, from like 70:1 at times and 30:1 at times, I was merely trying to show by using that shop manual, that there wasn't a specific continuous consumption rate of 50:1.
The way I wrote that post was completly taken out of context or I was merely mis-understood in the point I was trying to make.........:cheers:

 

[Dennis]

Oil Ratio

Hi ScubaDoo,
The ratios of 80to1 and 40to1 were nominal figures. I just used them to explain what I thought SEADOOSNIPE was saying which by the way I think he's correct. Like SEADOOSNIPE, I believe the rotax oil injection system provides the best engine performance, by far, compared to premixing which by nature doesn't take into consideration all of the different running conditions the engine is being subjected to. On the otherhand premixing is the safe thing to do if you have doubts about the injection system.
Yeah, my average ratio of 45 gal fuel to 1 gal oil statement may be a little incorrect. I forgot to factor in that fact that most people over fill the oil tank and about 10% of the oil they poured in comes out the tank vent and ends up in the bottom of the hull and that 10% doesn't count as consumed just wasted.LOL

Thanks, DAWG

 

[Dennis]

Sorry Seadoosnipe

HI LOUIS,
I just read your 10:30 reply and I know now that I totally misunderstood your previous post. (but you sounded so convincing!! LOL) If you promise to practice your writing skills I'll promise to practice on my reading. I'm also like Jethro..... I can read some readin'......I can write some writin'.... but I have a hard time readin' writin'.
THANKS, DAWG

 

[robin savell lloyd]

oil

I have put in about 25 gallons of gas, and no oil. The reservoir still shows it being full, or darned close to it. I may have put maybe a pint in there to top it off when I bought the gallon of oil...

Should I start adding some to the gas?

Makes me wonder if this is part the reason for last week's seize up...

BUT!!! The cylinders look really good, still have good crosshatching, so it seems like THEY are getting lubed enough.

25 gallon of gas and one pint of oil is what I was haveing a hard time seeing I have seen other engine manufactures spec 100 to 1 and then a few years recall fuel ratio should be changed to 50 to 1 it is unbeleiveable how long an engine can run if you mix it wrong but do not fall below say 75 to 1 now do not miss the point I do know that high rpms can ruen this whole idea

 

[scooper77515]

Sorry...

...to start a thread like this and then leave town...:cheers:

I will take a more "systematic" approach to my measurements. What I listed earlier is just "off the top of my mind" measurements, and could be wrong.

When I get the jet back together this weekend, it will get much more useage...and I will measure more closely.

I might go ahead and add a little oil to the gas, just in case oil flow is poor, and until I get a chance to verify that the oiling system is working up to par. I guess if it starts to smoke, I know I have it too rich and will just add some more gas to thin it out.

Interesting read about the variable rate...I didn't know this ski had that.

 

[seadoosnipe]

Laughter....!

You know Scott....I was thinking the same thing last night myself!....I thought to myself, where in the world is the one who started all this...:boxing_smiley:
I think you did a great job. We need comments like this, it generates forum debates and gets all the members involved in making their comments. I think my writing skills took a hit last night. I was very tired, had been up since the early morning hours.......that's my story and I'm sticking to it!...:rofl:
But seriously, do keep an eye on your oil system, especially with the age. I mark my vent hose off the rotary chamber, where the oil in the tank is equal to the oil in the hose, then I look for a drop in it.
Do put oil in your gas if your uncertain. It is better to smoke and foul plugs than it is to burn up your engine.
You should check the linkage to your injection pump if you removed the carbs, to make sure it is lined up for the correct flow...etc.......
Good luck and thanks for starting the good, healthy debate!...Great job to all that got involved.