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Author Topic:   Oil Consumption Rate

landhark04 posted 06-26-2009 11:07 PM ET (US)
[O]n a recent trip [a 1995 Yamaha 225 76-degree engine] burned 135 gallons of fuel and used five gallons of oil[.] [T]hat can't be normal--that's 24:1. What should the correct ratio be?
jimh posted 06-27-2009 08:36 AM ET (US)
Your gasoline to oil consumption ratio was 135/5 or 27:1.
The owner's manual for your motor should have details about the gasoline to oil ratio. Typically the ratio is around 50:1.
TransAm posted 06-27-2009 09:44 AM ET (US)
Your owners manual will likely not specify a overall gas/oil ratio since with the precision blend system, oil is consumed at different rates for different engine operating speeds. At higher engine speeds, the oil will be consumed at a higher rate with the inverse true. It does seem as though the injection pump may be overactive and should be checked. On the flip side, at least your engine is well lubricated, although your spark plugs will not have a very long life at that rate.
jimh posted 06-27-2009 10:06 AM ET (US)
In the Yamaha Precision Blend oil and gasoline mixing system, what is the mechanism by which the ratio of gasoline and oil are varied?
TransAm posted 06-27-2009 10:46 AM ET (US)
I do not know; I assume the ratio is proportionate to the engines operating speed. From my Yamaha owners manual:
The Engine used the YAMAHA PRECISION BLEND SYSTEM, which provides superior lubrication for all operating conditions. No fuel pre-mixing is needed {except during break-in/running ins.}. Simply pour gasoline in the fuel tank and oil into the oil tank."

Tom W Clark posted 06-27-2009 12:38 PM ET (US)
I agree, 27:1 is grossly excessive.
My 1989 "oil injected" Mercury 150s, which spend most of their running time at cruise speeds, consume oil at a 60:1 gas/oil ratio on average. I believe that is typical for all conventional two stroke outboards.
seahorse posted 06-27-2009 03:54 PM ET (US)
The big block Yamaha's like your 76° engine use more oil than the smaller block motors. Service literature from Ymaha training courses mention around 35:1 to 40:1 on the average.
Make sure your oil pump link arm is hooked up and adjusted per the service manual and that your pump is not leaking through the shaft seal at the motor.
The oil tank overflowing or a bad seal in the pump usually causes a smokey engine at low speeds.
seahorse posted 06-27-2009 04:03 PM ET (US)

quote:
In the Yamaha Precision Blend oil and gasoline mixing system, what is the mechanism by which the ratio of gasoline and oil are varied?

The oil pump is gear driven and the stroke varies by a cam moved by a lever conntected to a link between the carbuetor throttle shaft and the oil pump. Both rpm and throttle opening affect the oil pump discharge rate.
The pump is unique, the piston is stationary and the cylinder goes up and down according to the lever cam position. There is an outlet fitting for a hose to each intake and a check valve prevents a siphoning action or a "blow back" in case of a backfire.
landhark04 posted 06-30-2009 11:46 PM ET (US)
I decided to disconect the oil pump and run 50:1 mixture. Would this allow me to run the motor safely?
Peter posted 07-01-2009 06:56 AM ET (US)
I would not do that. The big block Yamaha V6s need more oil than 50 to 1 provides.
Buckda posted 07-01-2009 10:12 AM ET (US)
Is there any indication as to WHY the big-block Yamaha's from the 1990's required such a rich mixture? That seems quite a lot for a relatively modern motor. Our 194X Scott-Attwater 10 HP uses 24:1, but my 1973 Johnson 6 HP takes 50:1 (although I run it a bit rich due to age).
35:1 seems very rich to me.
What's the rationale?
Tom W Clark posted 07-01-2009 11:33 AM ET (US)
35:1 to 40:1 is remarkable. If the oil ratio is varied by the oiling system and those figures are averages, then just how rich is the fuel when the motor is operating at full throttle?!
If this is true, it is the only modern outboard I know of that requires fuel richer than 50:1. Not good if you want to premix.
TransAm posted 07-01-2009 12:12 PM ET (US)
Maybe this is the secret to the "bullet-proof" nature of Yamaha motors, ;-). Seriously, having owned 4 big block and 3 small block Yamaha V-6's, this is news to me. My motors, when properly tuned, never seemed to excessively smoke. My plugs are rarely fouled. Our old Mercury 150 would foul plugs regularly at 50:1 pre-mix. I'll probably be burning some serious fossil fuel over the Weekend; I'll see if I can't gauge how much oil I burn.
Tohsgib posted 07-01-2009 12:15 PM ET (US)
I have never heard or read anywhere that a modern outboard runs more than 50:1 Does anyone have a big block Yamaha manual or brochure that states what the mixture is? OMC quoted 150:1 @ idle to 50:1 @ WOT.
TransAm posted 07-01-2009 01:05 PM ET (US)
This specific information must be proprietary to some degree. The owners manual is silent in this regard. Whenever the question is raised in the manual, it simply says the motor uses Yamaha Precision Blend ratio. It does however specify that an additional 50:1 pre-mix be used after long periods of storage (until you can observe the oil tank pumping oil) and during 10 hours of break-in.
Tohsgib posted 07-01-2009 01:12 PM ET (US)
Then I would assume that 50:1 would be the correct ratio if pre-mixed.
TransAm posted 07-01-2009 04:37 PM ET (US)
I would not. If the info seahorse has presented is correct, 50:1 is 20%-30% shy of those recommendations.
Buckda posted 07-01-2009 05:23 PM ET (US)
TransAm - as an owner of a larger powerhead Yamaha engine, do you notice excessive oil consumption? I've boated with guys who have the 225's and not heard them complain about excessive oil use. This seems like a huge amount of oil for these motors to consume!!
TransAm posted 07-01-2009 05:38 PM ET (US)
Honestly, I have never given it a thought. As long as the engine was sucking oil, and I didn't have excessive smoking, I figured I was good to go.
Thinking further, when I re-fuel, I usually pump about 60-70 gallons in, an amount I will safely burn within a couple of weeks or so. And with that, I usually put in 4-6 quarts to maintain an acceptable oil level. On average, that works out to about 50:1. But I sometimes sneak a quart or 2 in between fill-ups if I'm digging through the storage area and want to clear it of extra oil. I'm going to try an look at this more closely and make a more measures account.
Other than that, I get the standard plume of smoke at start-up (hot and cold), but no fouled plugs, and the waft of smoke with a following wind at idle speeds, but nothing out of the ordinary.
Bella con23 posted 07-01-2009 05:53 PM ET (US)
My 1999 Mercury 225 EFI is burning 2 gallons of oil for every 50 gallons of gas.
I think I'm going to look into that.
Joe
Peter posted 07-01-2009 06:21 PM ET (US)
When I had my 2000 Yamaha 225 Ox66 it always seemed like it used a bit more oil than the 1987 Johnson 150 I had before it. Never measured it exactly but if the Johnson worked out to about 50:1 then 40:1 sounds about right. The Yamaha was rigged with a pretty large oil tank (about 3+ gallons) versus the 1.8 gallon tank connected to the Johnson so level changes on the Yamaha tended to be a little less noticible.
landhark04 posted 07-03-2009 12:57 AM ET (US)
well this is what I did, I disconected the oil pump linkage to the carb's and tie wrapped it off in the ideal position, and mixed a 50-1 ratio, this will give a small amount of oil injected into the carb's with the 50-1 mixture , I ran the boat out 60 miles offshore and back with no problem , little problem with motors idling, What do ya'll think , can i continue running them like this?
TransAm posted 07-03-2009 07:54 AM ET (US)
Sounds like you're going to an awful lot of trouble to run the engine in a manner not intended by Yamaha. I would guess Yamaha had some reason for programming the oil delivery in the manner they did. I would not alter it. You may be o.k., but then again, you may not be.
Pre-mixing is fine when you are assured the oil has thoroughly incorporated itself in the gasoline. If not, it has a tendency to accumulate on the bottom of a fuel tank. The engine can gulp down large amounts of unmixed oil and really foul things up.
landhark04 posted 07-03-2009 01:25 PM ET (US)
I understand what your saying, i recalulated my fuel to oil ratio, 166 gals fuel to 5 gal. instead of 135 to 5 if i figured right that would be 33/1 I've been unable to find info on what the right ratio is . Thanks for all the help for past and advance assistance Kevin
TransAm posted 07-03-2009 03:15 PM ET (US)
To my understanding, there is no right ratio. It seems the Precision Blend system injects oil at different rates for different operating speeds. So your average oil consumption will depend on your duty cycle. The average you are reporting now is very close to what Seahorse has suggested Yamaha training literature has cited as normal. I would plug the oil injection system back in and let it do what it was designed to do.
landhark04 posted 07-03-2009 11:29 PM ET (US)
I think your right Thanks again

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Author	Topic: Oil Consumption Rate
landhark04	posted 06-26-2009 11:07 PM ET (US) [O]n a recent trip [a 1995 Yamaha 225 76-degree engine] burned 135 gallons of fuel and used five gallons of oil[.] [T]hat can't be normal--that's 24:1. What should the correct ratio be?
jimh	posted 06-27-2009 08:36 AM ET (US) Your gasoline to oil consumption ratio was 135/5 or 27:1. The owner's manual for your motor should have details about the gasoline to oil ratio. Typically the ratio is around 50:1.
TransAm	posted 06-27-2009 09:44 AM ET (US) Your owners manual will likely not specify a overall gas/oil ratio since with the precision blend system, oil is consumed at different rates for different engine operating speeds. At higher engine speeds, the oil will be consumed at a higher rate with the inverse true. It does seem as though the injection pump may be overactive and should be checked. On the flip side, at least your engine is well lubricated, although your spark plugs will not have a very long life at that rate.
jimh	posted 06-27-2009 10:06 AM ET (US) In the Yamaha Precision Blend oil and gasoline mixing system, what is the mechanism by which the ratio of gasoline and oil are varied?
TransAm	posted 06-27-2009 10:46 AM ET (US) I do not know; I assume the ratio is proportionate to the engines operating speed. From my Yamaha owners manual: The Engine used the YAMAHA PRECISION BLEND SYSTEM, which provides superior lubrication for all operating conditions. No fuel pre-mixing is needed {except during break-in/running ins.}. Simply pour gasoline in the fuel tank and oil into the oil tank."
Tom W Clark	posted 06-27-2009 12:38 PM ET (US) I agree, 27:1 is grossly excessive. My 1989 "oil injected" Mercury 150s, which spend most of their running time at cruise speeds, consume oil at a 60:1 gas/oil ratio on average. I believe that is typical for all conventional two stroke outboards.
seahorse	posted 06-27-2009 03:54 PM ET (US) The big block Yamaha's like your 76° engine use more oil than the smaller block motors. Service literature from Ymaha training courses mention around 35:1 to 40:1 on the average. Make sure your oil pump link arm is hooked up and adjusted per the service manual and that your pump is not leaking through the shaft seal at the motor. The oil tank overflowing or a bad seal in the pump usually causes a smokey engine at low speeds.
seahorse	posted 06-27-2009 04:03 PM ET (US) quote: In the Yamaha Precision Blend oil and gasoline mixing system, what is the mechanism by which the ratio of gasoline and oil are varied? The oil pump is gear driven and the stroke varies by a cam moved by a lever conntected to a link between the carbuetor throttle shaft and the oil pump. Both rpm and throttle opening affect the oil pump discharge rate. The pump is unique, the piston is stationary and the cylinder goes up and down according to the lever cam position. There is an outlet fitting for a hose to each intake and a check valve prevents a siphoning action or a "blow back" in case of a backfire.
landhark04	posted 06-30-2009 11:46 PM ET (US) I decided to disconect the oil pump and run 50:1 mixture. Would this allow me to run the motor safely?
Peter	posted 07-01-2009 06:56 AM ET (US) I would not do that. The big block Yamaha V6s need more oil than 50 to 1 provides.
Buckda	posted 07-01-2009 10:12 AM ET (US) Is there any indication as to WHY the big-block Yamaha's from the 1990's required such a rich mixture? That seems quite a lot for a relatively modern motor. Our 194X Scott-Attwater 10 HP uses 24:1, but my 1973 Johnson 6 HP takes 50:1 (although I run it a bit rich due to age). 35:1 seems very rich to me. What's the rationale?
Tom W Clark	posted 07-01-2009 11:33 AM ET (US) 35:1 to 40:1 is remarkable. If the oil ratio is varied by the oiling system and those figures are averages, then just how rich is the fuel when the motor is operating at full throttle?! If this is true, it is the only modern outboard I know of that requires fuel richer than 50:1. Not good if you want to premix.
TransAm	posted 07-01-2009 12:12 PM ET (US) Maybe this is the secret to the "bullet-proof" nature of Yamaha motors, ;-). Seriously, having owned 4 big block and 3 small block Yamaha V-6's, this is news to me. My motors, when properly tuned, never seemed to excessively smoke. My plugs are rarely fouled. Our old Mercury 150 would foul plugs regularly at 50:1 pre-mix. I'll probably be burning some serious fossil fuel over the Weekend; I'll see if I can't gauge how much oil I burn.
Tohsgib	posted 07-01-2009 12:15 PM ET (US) I have never heard or read anywhere that a modern outboard runs more than 50:1 Does anyone have a big block Yamaha manual or brochure that states what the mixture is? OMC quoted 150:1 @ idle to 50:1 @ WOT.
TransAm	posted 07-01-2009 01:05 PM ET (US) This specific information must be proprietary to some degree. The owners manual is silent in this regard. Whenever the question is raised in the manual, it simply says the motor uses Yamaha Precision Blend ratio. It does however specify that an additional 50:1 pre-mix be used after long periods of storage (until you can observe the oil tank pumping oil) and during 10 hours of break-in.
Tohsgib	posted 07-01-2009 01:12 PM ET (US) Then I would assume that 50:1 would be the correct ratio if pre-mixed.
TransAm	posted 07-01-2009 04:37 PM ET (US) I would not. If the info seahorse has presented is correct, 50:1 is 20%-30% shy of those recommendations.
Buckda	posted 07-01-2009 05:23 PM ET (US) TransAm - as an owner of a larger powerhead Yamaha engine, do you notice excessive oil consumption? I've boated with guys who have the 225's and not heard them complain about excessive oil use. This seems like a huge amount of oil for these motors to consume!!
TransAm	posted 07-01-2009 05:38 PM ET (US) Honestly, I have never given it a thought. As long as the engine was sucking oil, and I didn't have excessive smoking, I figured I was good to go. Thinking further, when I re-fuel, I usually pump about 60-70 gallons in, an amount I will safely burn within a couple of weeks or so. And with that, I usually put in 4-6 quarts to maintain an acceptable oil level. On average, that works out to about 50:1. But I sometimes sneak a quart or 2 in between fill-ups if I'm digging through the storage area and want to clear it of extra oil. I'm going to try an look at this more closely and make a more measures account. Other than that, I get the standard plume of smoke at start-up (hot and cold), but no fouled plugs, and the waft of smoke with a following wind at idle speeds, but nothing out of the ordinary.
Bella con23	posted 07-01-2009 05:53 PM ET (US) My 1999 Mercury 225 EFI is burning 2 gallons of oil for every 50 gallons of gas. I think I'm going to look into that. Joe
Peter	posted 07-01-2009 06:21 PM ET (US) When I had my 2000 Yamaha 225 Ox66 it always seemed like it used a bit more oil than the 1987 Johnson 150 I had before it. Never measured it exactly but if the Johnson worked out to about 50:1 then 40:1 sounds about right. The Yamaha was rigged with a pretty large oil tank (about 3+ gallons) versus the 1.8 gallon tank connected to the Johnson so level changes on the Yamaha tended to be a little less noticible.
landhark04	posted 07-03-2009 12:57 AM ET (US) well this is what I did, I disconected the oil pump linkage to the carb's and tie wrapped it off in the ideal position, and mixed a 50-1 ratio, this will give a small amount of oil injected into the carb's with the 50-1 mixture , I ran the boat out 60 miles offshore and back with no problem , little problem with motors idling, What do ya'll think , can i continue running them like this?
TransAm	posted 07-03-2009 07:54 AM ET (US) Sounds like you're going to an awful lot of trouble to run the engine in a manner not intended by Yamaha. I would guess Yamaha had some reason for programming the oil delivery in the manner they did. I would not alter it. You may be o.k., but then again, you may not be. Pre-mixing is fine when you are assured the oil has thoroughly incorporated itself in the gasoline. If not, it has a tendency to accumulate on the bottom of a fuel tank. The engine can gulp down large amounts of unmixed oil and really foul things up.
landhark04	posted 07-03-2009 01:25 PM ET (US) I understand what your saying, i recalulated my fuel to oil ratio, 166 gals fuel to 5 gal. instead of 135 to 5 if i figured right that would be 33/1 I've been unable to find info on what the right ratio is . Thanks for all the help for past and advance assistance Kevin
TransAm	posted 07-03-2009 03:15 PM ET (US) To my understanding, there is no right ratio. It seems the Precision Blend system injects oil at different rates for different operating speeds. So your average oil consumption will depend on your duty cycle. The average you are reporting now is very close to what Seahorse has suggested Yamaha training literature has cited as normal. I would plug the oil injection system back in and let it do what it was designed to do.
landhark04	posted 07-03-2009 11:29 PM ET (US) I think your right Thanks again