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Author Topic:   Reputation of Automatic Oil Mixing Systems
Sfef84 posted 06-29-2010 11:00 AM ET (US)   Profile for Sfef84   Send Email to Sfef84  
I have a lead on twin 1990 90 hp Yamaha outboards that have the internal oil tank bypassed. I have heard about bypassing the VRO but never with a Yamaha. Yamaha's built in oil tank systems have a pretty good reputation don't they?
jimh posted 06-29-2010 12:12 PM ET (US)     Profile for jimh  Send Email to jimh     
The automatic oil mixing system in a c.1990 Yamaha 90-HP does not have many reports of failures. However, when dealing with any 20-year-old motor, and particularly with a 20-year-old motor that was unscrupulously modified by some unknown previous owner or mechanic, making an accurate inference about how well its disconnected automatic oil system will operate if re-connected is not a sure thing.

The oil reservoir tank in a 90-HP Yamaha is probably under the engine cowling, and the feed to the oil-mixing pump is probably a gravity feed. I am not familiar with the precise details of the oil mixing pump on that motor, but my impression of the reliability of the pump--from a general lack of mention about replacement or repair--is that is a good component. I operated a pair of Yamaha 70-HP motors, and I never gave a thought to the automatic oil mixing. There is a bleed valve on the oil mixing pump to ensure there is no air in the feed from the reservoir, and, other than opening that bleed screw once of two just from curiosity, the pump required not maintenance, repair, calibration, or other service.

jimh posted 06-29-2010 12:24 PM ET (US)     Profile for jimh  Send Email to jimh     
If you need advice on making a repair, use the REPAIRS/MODS discussion area. We can offer advice there. Here in THE GAM we can discuss the reputation, but not the repairs or modifications.
jimh posted 06-29-2010 12:29 PM ET (US)     Profile for jimh  Send Email to jimh     
Oops--Meant to say we cannot offer repair advice here.
Tohsgib posted 06-29-2010 01:43 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Many people disconnect when they get older or a part breaks that is too expensive to justify. With a 90hp oil use will be minimal, on a V6 VRO is monetarily justified.
Sfef84 posted 06-29-2010 03:10 PM ET (US)     Profile for Sfef84  Send Email to Sfef84     
Thank you for the replies. Fortunately, original hours are 355 on each motor. They had been winterized in 1997 and stored in a barn after the owner passed away. The current seller bought the 24' cat and motors a couple months ago, had a dealer rebuild carbs, new impellar, pump lower unit seals etc only then, deciding to purchase larger HP four strokes. While the motors were receiving their facelift, the oil tank bypass procedure was completed.

He said the auto oil injection system works fine but " doesn't want to burn up the motors while 30 nm offshore." Sounds like he had a VRO pump failure in the past and is scared for life.

contender posted 06-29-2010 03:20 PM ET (US)     Profile for contender  Send Email to contender     
I do not know if this will help but, I have a 1990 250 Yamaha and the oil pump is mounted on the outside of the oil tank. The oil tank has a place for the oil pump to fit into. The early Yamaha oil system was better than the Evinrudes vro, The Yamaha system would push/pump the oil to the engine/carbs to be mixed, while the Evinrude was a suction system, that would mix the oil in the pump. I think you could bypass any engine oil pump if it is done correctly. You would have to disconnect any lower oil sensors on the Yamaha(do not know about Mercury). And just make sure you mix your oil...
jimh posted 06-29-2010 05:56 PM ET (US)     Profile for jimh  Send Email to jimh     
I do not think there is strong correlation between the oil system on a 250-HP Yamaha and a 90-HP Yamaha. For starters, the Yamaha 250-HP uses a remote oil tank and an electric pump, which are both missing from the 90-HP. To make an inference about the 90-HP based on anecdotal evidence of a 250-HP engine is not soundly based.

I don't put much faith in gratuitous comparisons of which brand of oil system was better, as often what happens is the original oil system, the EVINRUDE VRO from the early 1980's is held up for comparison to some oil system that did not appear for twenty years later. I have made a very detailed comparison on oil systems and assessed their components, the manner in which the operate, and their various changes. See:

http://continuouswave.com/whaler/reference/OMCvMERC.html

In that comparison I have to say the OMC faired very well, and it was a simple and more foolproof system. I have not made a comparison to Yamaha, in part because I cannot recall anyone even asking about problems in Yamaha automatic oil systems or recommending they be disconnected.

As far as reputation, again, I think Yamaha's automatic oil system reputation is very good. However, now that I hear the engines under discussion sat without use from 1997 to 2010, a period of 13 years, I am even less inclined to offer any wisdom about how these particular engines will work if restored. Components, particularly rubber components, which sit for a long time are often deteriorated by age and exposure to air at a faster rate than if they were in use.

Tohsgib posted 06-30-2010 12:18 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Suzuki invented oil injection.
Tohsgib posted 06-30-2010 12:19 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
PS I would be more worried about the shift linkage rod than the disconnected VRO. 1990 were still steel, not SS. If not replaced, they will be soon and NOT cheap due to powerhead removal.
Sfef84 posted 06-30-2010 12:26 PM ET (US)     Profile for Sfef84  Send Email to Sfef84     
Thanks Toshgib,

In my search for a yammie, I found a few motors with that problem and the owner says "Don't worry about it, the mechanic says it will only be $300." The mount on top of the lower unit that secures the shifting bar was completely gone. I said "Thank you for your time." haha

jimh posted 06-30-2010 11:17 PM ET (US)     Profile for jimh  Send Email to jimh     
Nick--Please give more facts and background on the Suzuki oil mixing system, particularly its date of introduction. I believe OMC introduced the VRO in c.1984. Does Suzuki pre-date that?
Tohsgib posted 07-01-2010 12:20 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Yes. My 1981 had oil injection. I want to say 1974 or 1977 they started in outboards.
Tohsgib posted 07-01-2010 12:28 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Looks like 1980:

http://media.suzuki.com/marine/history/

jimh posted 07-01-2010 01:34 PM ET (US)     Profile for jimh  Send Email to jimh     
In 1980 were Suzuki outboard motors being imported and sold in North America?
Tohsgib posted 07-01-2010 01:37 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
Yes...they came here in 1977, same year Yamaha came ashore as Mariner.
jimh posted 07-01-2010 01:39 PM ET (US)     Profile for jimh  Send Email to jimh     
I also read recently about a feature of the Yamaha oil mixing system: it never really mixed the oil with the gasoline. The oil was introduced downstream of the carburetors. The advantage of this approach is the oil-gas mixture is never present in the carburetors, the carburetor bowls, or the carburetor jets. This is claimed to reduce problems with fouling of those devices when the gasoline evaporates and possibly leaves behind an oil residue. Any confirmation of this from our Yamaha experts?
Tohsgib posted 07-01-2010 02:31 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
My 1981 Suzuki was like that but my 1990 90 Yamaha was not as far as I remember it fed into the carbs. The Suzuki was an internal tank unit like the smaller engines and had 4 hoses going into the block somewhere. Most systems I owned have it going into the fuel pump, carbs or intake.
contender posted 07-01-2010 03:13 PM ET (US)     Profile for contender  Send Email to contender     
Tohsgib, I just drop my lower unit on my 1985 140 evinrude, I can swear both my shift rod and drive shaft were stainless. I even took the shift rod out to repalce the seals on it....
Tohsgib posted 07-01-2010 03:15 PM ET (US)     Profile for Tohsgib  Send Email to Tohsgib     
That is an OMC...we are talking early Yamahas.

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