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Author Topic:   Remove Oil Mixing System
kgregg posted 12-28-2006 09:43 AM ET (US)   Profile for kgregg   Send Email to kgregg  
Hi All. I have a 1991 Outrage 19 with 1991 Mercury 135-HP two-stroke. After having my mechanic repair and winterize the boat, he mentioned the option of removing the oil [mixing] system (two oil tanks, pump, alarm, etc.) and simply adding oil to the gas when I buy gas. I have 62 gallon internal gas tank. I'm generally in favor of the idea [of removing the oil mixing system] for several reasons. I may have him make this change before the spring. What do you think of the idea? How do you two-stroke owners mix your oil? Thanks and Happy New Year! Kevin.
Binkie posted 12-28-2006 10:53 AM ET (US)     Profile for Binkie  Send Email to Binkie     
If it ain`t broke, don`t mess with it.


kgregg posted 12-28-2006 10:58 AM ET (US)     Profile for kgregg  Send Email to kgregg     
My oil injection system has given me problems from time to time. While it isn't broken, it is far from ideal. The low oil level alarm sounds (false alarms) too often. (The level of oil in internal tank needs to be at 100% full all the time). The external oil tank broke once (while at speed) spraying oil all over the splashwell and prematurely ending a day of boating. Removing this system would simplify my boating a great deal. I don't really see a problem adding a gallon of oil (for example) when I buy X gallons of gas.
jimh posted 12-28-2006 11:28 AM ET (US)     Profile for jimh  Send Email to jimh     
I would be interested to hear what the reason are which would tend to make one want to remove the automatic oil mixing system.

In favor of retaining the automatic oil mixing system, I see that:

--pre-mixing oil into the fuel can be awkward when the volume of the tank is large. Large amounts of fuel and oil have to be mixed as they are introduced to the tank, else oil may separate and settle to the bottom of the tank;

--pre-mixing is prone to failure due to negligence or error in the mix ratio, up to and including having forgotten to add any oil when gasoline is mixed;

--pre-mixed fuel in a tank is not useful for other purposes, such as using it in other types of engines.

--there is no alarm system which monitors the fuel to see if it has been pre-mixed and in the proper ratio

--there is no good data that shows that the chance of human error is less than the chance for mechanical error in the automatic system.

kgregg posted 12-28-2006 12:19 PM ET (US)     Profile for kgregg  Send Email to kgregg     
This decision is not a "done deal" by any means.

Yes, I would have to pay close attention when filling the tank to ensure I add correct amount of oil.

I've never needed to remove gas from 62 gallon tank in order to use it in some other engine. I have 6 gallon gas cans for that purpose.

I forgot to add that the last time I ran the engine (on the muffs), a 6 inch length of hose between the small oil tank and the engine failed, dumping oil all over the place. I've spilled way too much oil in the few years I've owned this boat. (and, no, I am not a klutz).

kamie posted 12-28-2006 02:33 PM ET (US)     Profile for kamie  Send Email to kamie     
If you fear the system failing then removing it an going premix will eliminate the fear. It will also eliminate the result of having the system fail to mix oil and gas of which the outcome is a new powerhead/new outboard.
efduffer posted 12-28-2006 10:47 PM ET (US)     Profile for efduffer  Send Email to efduffer     
I had the same kind of flakey and just uneasy relationship with my [automatic oil mixing system]. Uneven consumption between engines, false alarms, weird leaks and the space it consumed. I disconnected them and haven't looked back. I know what I'm going to put in the tank ahead of time, prepare a concentrated mix and add it during fueling. This is usually two quarts of oil and two quarts of gasoline mixed well, then dumped in just ahead of adding 24.5 gallons of gasoline to the tank.

Not worrying about alarms sounding, oil tanks and hoses leaking, mixing pumps failing, etc has removed a great deal of anxiety and added a lot of pleasure to my trips.

I also don't have to worry as much about buying the top-grade 2-stroke oil to keep the VRO system in order. My engines were built at the beginning of the VRO age and I feel confident that even today's off-brand oil, if I choose to use it, is as adequate, if not moreso, than the oil available at the time the engine was produced and was designed to use.

A2J15Sport posted 12-29-2006 12:22 AM ET (US)     Profile for A2J15Sport  Send Email to A2J15Sport     
I've owned numerous engines that were oil injected and numerous engines that were not.

My preference is for the oil injection, hands down. I've never had a minutes trouble with any of them-Merc./OMC/Suzuki/Yamaha. However, I maintain them, few people do.

The biggest cause of failures and false alarms is water intrusion into the tanks. Water is a poor lubricant in an engine. In addition, just like fuel lines, oil lines need to be maintained or replaced.

andygere posted 12-29-2006 01:43 AM ET (US)     Profile for andygere  Send Email to andygere     
Having owned a 2-stroke Mercury of similar vintage, here's my advice: Keep the oil injection, but replace every bit of tubing (clear and black) in the system, whether it needs it or not. My experience is that the injection systems are quite reliable, but the cheap plastic tubing gets brittle and can crack and leak.
Steve Leone posted 12-29-2006 09:47 PM ET (US)     Profile for Steve Leone  Send Email to Steve Leone     
Another point for keeping the oiler is that is will only blend in the required amount of oil as the engine needs it. For example, at idle it will not be blending as much as at mid to full rpms. Thus it is more efficient to use an oil injection system than to pre-mix your fuel. If you do not care for the oiler on your Merc, nor the bank of alarms involved, you may aquire an Mercury Auto Blend oiler. This hooks up outside the outboard and does away with the conventional set up. It is driven electronically and pre-mixes before the fuel enters the outboard. I have a good one if you are interested in this conversion, and I will sell it to you cheap. Steve.
vinay posted 12-30-2006 01:38 AM ET (US)     Profile for vinay  Send Email to vinay     
If I were you I would try to keep it. Changing the tubing as mentioned is a good idea. I find that adding a fuel conditioner makes a lot of difference in the performance, if it is working in the first place. Gas, in time, create gummy deposits that interfers with the mechanic of the engine. So fix it and treat it.
merc125 posted 12-30-2006 10:56 AM ET (US)     Profile for merc125  Send Email to merc125     
Steve, is that auto blend universal to all V6 mercury? If kgregg doen't want it I might interested. Thanks MartyD
longboarder posted 12-30-2006 10:39 PM ET (US)     Profile for longboarder  Send Email to longboarder     
Get rid of [the automatic oil mixing system}. Mix your own gas. Is [pre-mixing oil with gasoline in the proper ratio before using it in your fuel tank] that hard? If [the automatic oil mxixing sytems] fails, and your alarm fails, your engine will be shot. [The automatic oil mixing system] was the first thing I removed when I got my Boston Whaler boat.
jimh posted 12-31-2006 09:11 AM ET (US)     Profile for jimh  Send Email to jimh     
longboarder's comments are a good argument for NOT removing an automatic oil mixing system. As he points out, most automatic oil mixing systems include alarm systems which monitor the operation of the system and alert the operator if there is a problem. When you remove the automatic oil mixing system, you also remove the alarm system which is monitoring it. At that point the operator becomes the alarm system. The engine will have no way to determine if there is oil in the gasoline--it leaves that to the operator.

The degree to which an automatic oil mixing system can properly monitor its own operation varies. Some systems have better alarms than others. For a good comparison on the OMC and Mercury systems, read

Automatic Oiling System: OMC/Bombardier versus Mercury

longboarder also inquires about the degree of difficulty required to properly pre-mix oil and gasoline. In my experience, the process of pre-mixing oiling and gasoline can be awkward and inconvenient. It is certainly more inconvenient than just adding gasoline. On my Boston Whaler boat the fuel tank fill is located on the cabin superstructure, and it is not easily accessed from inside the boat. It is also not easily accessed from a dock unless the dock is a floating dock. Unfortunately, most of the fuel docks we encounter have a deck height that is substantially higher than the optimum height, and fueling can be rather awkward. If I had to simultaneously hold a funnel and pour oil into the tank while adding gasoline, it would be extremely awkward to accomplish at most of the fuel docks I encounter.

Similarly, when I add fuel to the boat while it is on the trailer, the location of the fuel fill is quite awkward. I would probably have to carry a small ladder with me in order to be able to use a funnel and pour oil into the filler while adding gasoline.

I have had occasion to need to pre-mix oil and gasoline, and in those instances I have used the technique of first making a very rich mixture of oil and gasoline (perhaps 1:2) in a separate small tank, pouring that mixture into the main tank, then adding the remaining portion of the gasoline. This requires carrying around another small tank to use for the pre-pre-mixing.

If your motor has a working automatic oil mixing system, I would be inclined to retain it. But be sure to give it good maintenance and keep it in working condition.

bms1939 posted 12-31-2006 05:33 PM ET (US)     Profile for bms1939  Send Email to bms1939     
I had the twin outboard engines on my other boat rebuilt by a very reputable re-builder seven years ago. He gave me a one year warranty on the power heads, he refused to warranty them with the vro's hooked up. He told me that 50% of the engines he rebuilds were due to fuel/oil pump failures. He told me he would hook them back up after the warranty ran out. After the year mixing the fuel I said to myself why would I hook these things up if he won't warranty his engines with it hooked up? Other than a little extra smoke at idle it's been fine for seven long seasons. I put on about 1-2 hundred hours a season 9-10 months a year. I replace the plugs only at the end of the season, I have never fouled a plug. I trailer the boat so the fuel and oil separation has never been a problem. If your not comfortable with the system then go for it!
longboarder posted 01-07-2007 09:26 PM ET (US)     Profile for longboarder  Send Email to longboarder     
EXACTLY what bms said. Not only that the mixing units run richer and will foul the plugs/rings, ect... So, I guess to each his own. I myself will put my faith and $13,000 motor in myself. As far as an alarm, you don't need the autoblend hooked up to have an alarm.
skred posted 01-08-2007 04:00 PM ET (US)     Profile for skred  Send Email to skred     
What did all those boaters do all those years before oil injection and VRO? Judging by some responses here, there must've been a LOT of fried engines (although I certainly don't remember that being a common occurrence). I had a Mercury-built Force 90 on my Montauk (I know - I know... spare me...) The motor required pre-mixed fuel/oil. I ran that boat/motor for over 5 years and averaged hundreds of hours in my shortest season. Never had a single problem. I agree, "Operator Malfunction" is a thing to be reckoned with, but - c'mon, now: I had a little card in my console with the "ounces per gallon" numbers on it. It wasn't rocket science to look up the oil quantity for - say 8 gallons, or 10 1/2 gallons, pour the required oil (out of a recycled 1-quart oil bottle with visible markings on the side) into the tank then stop the gas pump at the predetermined gallon quantity. The fear of the oil settling out of the mix is nonexistent: if you tow your boat any more than 3 blocks to launch, that movement alone will re-mix the fuel.
I never regretted the pre-mix requirement on my boat, and felt a lot more secure than with my first oil-injected motor, which gave a lot of false alarms, and way down deep, I had a vague mistrust of its dependability.
I say - if you're constantly worrying about your oiler's dependability, disconnect it, but keep it stashed away, in case you change your mind or decide to sell the boat/motor (easy thing to reinstall the system for a prospective buyer.
towboater posted 01-08-2007 05:00 PM ET (US)     Profile for towboater  Send Email to towboater     
I had 3 93 150 Black Max for a CPD 22 (1 spare BECAUSE of the oil risk) and did quite a bit of research on the process of removing the auto oilers.

I found removing the auto oiler from that series of Mercs is pretty common. In fact, I called 2 different outboard mechanics and both told me how to do it from memory! No, they didnt go look at a book, they just reeled off the info off the top of their head. Sigh.

AS Leone mentions, (this info is in the manual also) the auto oil injector varies at different RPMs. I dont have the numbers right now but basically, 50 to 1 is a little thick at idle. This is a problem for me because I want to troll at times and DONT want to carry a kicker. Premix gas is likely to load up the engine at low rpms faster than auto oiler will.

The problem is internal, the oil pump impellers are PLASTIC and PLASTIC is not good on a hot engine. BOO on you Merc! Replacing the plastic impeller with metal is labor intense, pretty spendy.

As mentioned several times, it it aint broke, dont mess with it. I am not going to remove the oiler. But if that sucker so much as hickups, the oiler is gonna go. When that happens, rest assured fellas, I can do the simple mix math and will carry a spare set of plugs.

BTW, I am shopping for a worn out BLACK MAX to rebuild, which will include a metal oil pump impeller and become a fairly inexpensive plug n play spare engine for my purposes. 18 ft CPD.


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