Johnson VRO pump

[Eric Wettschreck]

Some of yous guys out there probably know I've had a few problems with my motor this summer. I have a 87, 70 HP, Johnson VRO. I've heard of guys bypassing the VRO pump and just running premix gas from the tank.

My question for those in the know is, does a guy just remove the VRO pump, and run the fuel line directly to the carb inlet hose that comes out of the VRO pump??? Is it really that simple???

Help me help me. My VRO pump is just leaking all over the place and if I can just bypass it that is what I would rather do.

[PierBridge]

Being you have an 1987 which is VRO2 not the original VRO that did have many problems one being being no low oil alarm I would just get a new pump (# 5004558) if it were me there really is NO reason to bypass the VRO2 system it's actually pretty bullet proof.

VRO gets blamed for almost every problem a person has with a VRO engine most if not ALL the problems have nothing to with the BIG BAD VRO system especially VRO2.

Anywho if the VRO is bypassed by disconnecting and plugging/capping the oil feed to the vro pump and disabling the vro alarms and the original pump is not in good operating condition ,it will need to be rebuilt or replaced with a conventional style fuel pump to perform as a 50:1 pumper.

Again I would just replace the pump and not mess with the premixing hassle.

By the way thats a great motor...

[Valv]

PB I disagree with you, the original VROs up to early '90s were cause of many motor damages since they quit providing lubrication. Many, many motors blew up because of this.

Newer models have been fixed and they reached a high level of reliability, but not the early models

Anyway, returning to Boilerguy motor, PierBridge has the right way to bypass it, but you might have to replace the pump or have it rebuilt since VRO is part of your fuel pump. You cannot eliminate physically the unit.

[PierBridge]

There definitly were problems with some of the earlier VRO pumps but NOT with VRO2 introduced in 85 and later models and the pre 85 problem was solved with the updated pumps!

The following article was published as a reprint from a Bass & Walleye Boatsmagazine article in Jan. 2000, and Trailer Boats magazine in Feb. 2000.

The Association of Marine Technicians (AMTECH) reprinted it in a newsletter a couple of years agowith permission from the magazines and the author Bill Grannis, an AMTECHmember:Whenever there is a gathering of boaters, the conversation usually turns toengines, then gravitates to stories about problems. One of the bones OMCowners like to pick concerns the oiling system. A typical conversation thatwe've all heard at one time or another might go something like this:"Yeah, my boat smokes like the ****ens at low speeds and fouls the plugs,"bemoans one boater. "Must be that worthless VRO pump acting up.""Uh huh, my neighbor had a blown engine," quips another. " Took out 2cylinders on his V6. the mechanic told him the VRO went bad. He didn't getan alarm or anything.""Come to think of it," the third member of the group chimes in, " mybrother- in-law's offshore rig with twin outboards must have a flaky VRO;one motor always uses more oil than the other.""My engine is hard starting at times," says a fourth angler, "the VRO pumpmust be getting weak and the warning horn blows constantly whenever I run atfull throttle on my 150."The truth of these stories is that none of the symptoms described is thefault of the VRO, yet the poor VRO pump gets the blame. Each rig has adifferent problem that is blamed on the oil pump because of misunderstandingand misinformation. Even many "experienced" mechanics do not have theknowledge of how the system operates and are quick to blame something thatis unfamiliar to them.For instance, the first boat owner's problem is an air leak somewhere in theboat's fuel system causing "foamy" fuel instead of a solid column of liquid.This aerated gasoline has less volume and less resistance causing the fuelpump diaphragm to cycle faster. Each cycle pulses oil into the foamy mix,increasing the oil:fuel ratio to the carbs creating a smoky exhaust. Themechanic of the second guy's neighbor did not understand that the VRO mixesthe fuel and oil internally then delivers the mixture through the fuel linesto each of the carbs. Since each carb receives the same oil to gas ratio,the VRO cannot cause only two cylinders to fail. Since the VRO did notmalfunction, there was no alarm to sound. On the other hand, thebrother-in-law's motors have two different year's pumps on them. The latermodel VROs pump more oil at low speeds than the original ones do. The lastguy blames the VRO because he once had a car with a weak fuel pump and areplacement cured its hard starting problem. Actually, he only needs arefresher in the correct starting procedure. As for the constant soundinghorn at high speed that stops when slowing down, that's a fuel restrictionwarning, not a VRO malfunction. A lack of oil flow is a pulsing on and offhorn every second or so. A decal is available (# 335707) for the dashboardthat illustrates the different warning signals and what they mean.A LITTLE HISTORY: OMC introduced the VRO on the V-4 and V-6 engines in 1984.The pump consisted of a combination oil pump and fuel pump actuated bycrankcase pulses through an air motor. Gasoline reformulation in those earlyyears contained alcohols and solvents that softened the internal rubbercomponents and caused pump failures and damaged engines. Back then, nocompany had alarm systems for a pump failure or loss of oil flow. OMC tookcare of the blown powerheads and improved the pumps considerably.The VRO2 was introduced in 1986 and included a "no oil flow" alarm. Changesincluded an electronic circuit to compare the oil pulses with the engine'srpm, a better oil pump piston, alcohol resistant seals, and a brown fueloutlet for recognition. Unfortunately, the damage was done. Publicperception fed by uneducated mechanics put the blame for almost every engineproblem on the VRO. No matter what happened to a motor, someone would utter".must be a bad VRO." Actually, the much-maligned pump is very simple andreliable. It consists of four basic sections: the air motor, a fuel pump, anoil pump, and a "no oil flow" alarm system. The air motor converts thepressure and vacuum pulses from the crankcase to a linear motion. Thesepulses are routed through a pair of check valves above the lower grayfitting. One directs pressure cycles to one side of the air motor's pistonand an inverted check valve directs the vacuum cycles to the opposite side.Each engine revolution moves the piston incrementally to one side of the airmotor chamber and compresses the large spring. When the piston nears the endof its travel, a small spring unloads a poppet valve located in the middleof the piston assembly. The pressure on one side of the piston rushes intothe vacuum side as the large spring quickly pushes the piston back to itsstarting point. As the throttle is advanced, the pressure pulse getsstronger because of the increased airflow through the crankcase. This backand forth motion of the air motor's piston is what powers the fuel pump andthe oil pump. At idle and low throttle settings, the weaker crankcase pulsescause shorter piston movements, which in turn, pump less oil with eachcycle. As the throttle opening increases, the stronger crankcase pulsescause greater piston travel resulting in longer oil pump strokes. Thatmeans, more oil is delivered increasing the amount of lubricant in the fuelup to a 50:1 ratio. The fuel pump, which is located in the middle chamber ofthe VRO, consists of a push-pull piston & diaphragm with a flapper valve andan inlet check valve. A rod connects the fuel pump piston directly to theair motor piston and the two chambers are sealed from each other by ano-ring. As the back and forth motion is generated in the air motor, thedouble-action fuel pump's piston & diaphragm is pushed and pulled by the rodcycling fuel to the carburetors. Gasoline is drawn into the blue area of thechamber, travels through the piston's flapper valve, and is pressurized inthe green section on the following stroke. The oil pump is directlyconnected to the fuel pump piston and diaphragm so they work in tandem. Aswith the fuel pump, oil is drawn in through the inlet fitting and a checkvalve as the air motor starts its travel. On the return stroke, the oilpressurizes, exits directly into the fuel chamber, and is blended whileenroute to the carbs.DISTINGUISHING VROs: Of all the traditional two stroke outboards producedworldwide, OMC products have the only automatic lubrication systems with a"no oil flow" alarm. The VRO's electronic circuitry compares the rpm of theengine to the number of pressure pulses from the oil pump piston. As the oilflows into the fuel area, the pressure moves a small piston that actuates asteel pin in the alarm module. The pin's movement is detected electronicallyand "counted." If the engine revolutions exceed the preprogrammed oil pulseratios, the warning horn is activated sounding a rapid on and off sequence.Since 1993, the VRO is actually called an oil metering system (OMS). Theratio averages about 60:1, slightly leaner at idle and slightly richer atfull throttle. The older pumps idled between 150:1 ( prior to 1990) and100:1 ('90-'92 ) then richened up to 50:1 as the engine load increased. Theyare recognized by the brown fuel outlet fitting and/or a wiring harnessattached to the alarm module. The original VRO from '84 and '85 had a blackfuel outlet fitting and no wiring. OMS pumps have a blue/gray outlet nippleor a blue/gray pulse nipple, or a black fitting held in place by an ovalmetal bracket and two Torx headed screws. To simplify things just rememberthat the air motor converts the crankcase pulses to a back and forth motion.Directly connected to the air motor is the fuel pump and the oil pump. Thetravel of the air motor pumps the fuel and the oil together to thecarburetors and the alarm system monitors the oil pressure counts. Just likemanually premixing the oil and gas, the VRO (OMS) automatically does thesame thing and sends that fuel mixture to the carburetors.PREVENTIVE MAINTENANCEThere is no mechanical maintenance that has to be performed on the pumpitself, but the VRO system should be inspected occasionally for crackedlines, leaks, and broken clamps. One of the most common causes of enginefailure is water in the remote oil tank. Condensation and spray can build upover time and, like water in a fuel tank, it stays on the bottom to besucked up at the worst possible moment. Water pumps through the system aseasily as oil, so several time a year use a turkey baster to draw off somefluid from the base of the tank and squirt it into a clean jar. Look forsediment or water settling to the bottom of the container. If you see anysigns of contamination, the tank should be flushed clean, the filter(#174377) changed, and the oil line purged. Be sure to read and understandthe service manual before doing any of these procedures. If an oil tank isexposed to the elements such as in an open boat, installing the tank insidea covered battery box will protect it from spray. You can also replace theclear plastic cap with the later model's solid black filler cap (#176217)that provides much better water intrusion resistance. The oil line should beOMC's ¼-inch I.D. inner "rubber" hose (#333485) without any splices. Earlysystems had a smooth vinyl oil line that hardened after a few years andsometimes caused air leaks. (Some installations even had 5/16-inch fuel linesqueezed down over the smaller fittings.) These air leaks can also trigger"no oil" alarms, commonly at startup, idle, and trolling speeds.Another service tip is to avoid Ty-raps or worm gear hose clamps on thissystem. The ratchet clamps ( #322654) give the best seal and full 360-degreeclamping action. Late-model OMCs use a double-wire wound spring clamp(#339277) that also works well in keeping lines air tight. Air leaks and/orfuel restrictions will affect the VRO and usually show up as excessive oilconsumption, smoking, and fouling plugs. If air gets into the fuel, itcauses a foamy solution, similar to a head of beer in a tall glass. ( Avapor lock situation does the same thing ). The volume of liquid fuel isless and the oil delivered is the same as for a full chamber of fuel. Nowyou have richer gas oil mix with its resulting symptoms. A fuel restrictionsuch as from a bad anti-siphon valve, kinked line, or a partially pluggedfilter does not allow a full charge of gas to be drawn into the fuel pumpcavity. Again, you get the full shot of oil mixing with less gas. This isalso the reason to /not/ disconnect the gas line and run the engine "dry".As you run out of fuel, the oil still pumps, filling the lines and carbswith your favorite TC-W3 lubricant. Since the VRO depends on crankcasepulses to operate, it is susceptible to backfires from a lean runningcylinder or an out of tune engine. If your motor is older than a 1993, makesure it has the blue colored pulse limiter to protect the air motor and thecheck valves in the pump. Follow the pulse line from the VRO to the engineblock and look for a hex shaped fitting threaded into the crankcase. If ithas a black face on it, replace it with a blue style (part # 435009). Thecrossflow V-6s have a pulse limiter with a fitting at each end and splicedin line with the VRO to crankcase hose. The inline replacement is part #435010.Since 1986 (and on updated '84s & '85s), the pumps have an alarm system thatoperates off the alternator or tachometer circuits. Occasional checks shouldbe performed to make sure the charging system, warning horn, and relatedparts are operational. The quickest and easiest test is the grounding of thetan overheat temp switch wire to the engine block. To do this, turn the keyon, motor not running, and use a jumper wire to ground the tan wire from themotor harness and listen for the warning horn. It should be a loud steadytone. On 1996 and later engines with a SystemCheck® gauge, only the "hot"light will come on, but no horn unless the motor is running. With theSystemCheck® equipped motors you will have to disconnect the OMS (VRO) fourwire connector and carefully ground the tan motor harness wire lead toilluminate the "no oil" light. The warning horn tone sequence tells if aproblem is occurring while operating the engine. A rapid on - off sound is a"no oil flow" indication. One beep every 20 to 40 seconds is a low oil levelin the remote tank. Of course a steady tone at all speeds is an overheatcondition. On V-6s a constant horn at high speeds that disappears instantlywhen the throttle is pulled back indicates a fuel restriction. Looseconnections can also cause erroneous "beeps" and the most common opencircuits are battery cables with finger tightened wing nuts instead ofstainless steel hex nuts and lock washers tightened with a wrench. Incorrectspark plugs occasionally cause false warning signals, too. Use only the "Q"style suppresser plugs recommended by OMC for your motor. Resistor plugs arenot the same thing and may be the source of problems. The factory does notendorse spark plug manufacturer's conversion charts.SYSTEM UPGRADES: In 1996, the SystemCheck® warning gauges were introduced. Atach with four warning lights or a dash-mounted gauge with the same lightsshow the type of malfunction that is occurring by which LED is illuminated.The horn sounds for 10 seconds when a fault occurs and the proper lightstays on until the problem is corrected. There are indicator LED's foroverheat, no oil, low oil, and check engine, which means a fuel restrictionin a V6 carbureted motor. By the way, the SystemCheck® can be adapted (withaccessory kit # 176709) to any engine with a four-wire VRO pump. Evenbetter, there's a new VRO (OMS) pump that can be used to upgrade all theprevious years and model outboards. The new pump (# 5004558) contains variousfittings for different outboards, and each internal part is replaceable foreasier and less expensive servicing. Part number #5004559 updates all earlythree-wire VROs except those found on the two-cylinders. For thoseoutboards, kit # 5004562 is used. OMC also makes a wiring harness adapter (#174710) for the 1984 and 1985 engines that did not have any warning systems.Each OMC (VRO) kit contains the parts needed including a new pulse limiterto install the system correctly.So, contrary to boat ramp banter, VRO is a simple and reliable oiling systemthat has been standard equipment on most OMC outboards from 40 to 300horsepower for the past 16 years. Most of the misinformation and "scaretactics" about its reliability originate from those who do not understandhow the system works-or fail to keep it maintained.SERVICING: Since 1991, the OMC factory service manuals include atroubleshooting chart and a section on how to test, take apart, and servicethe VRO pumps. Besides Torx screwdrivers, you will need a pressure and avacuum source to test the integrity of the check valves and diaphragms. CDIElectronics' #551-34PV gearcase vacuum/pressure tester work well, as does aSnapOn YA-4000 or the old Stevens pumps.Even though they are not listed in the parts catalogs, most of thediaphragms are interchangeable. The air motor diaphragm kit is part number435921 and the fuel pump repair kit is 436095. For those who premix theirfuel and oil, these kits allow the repair of the fuel pump section, avoidingthe high cost of a new assembly or the replumbing and rigging of one or twotraditional style fuel pumps.Do not interchange any of the springs with other pump assemblies. They arecalibrated for each model of pump. The latest#5004558 pump is a universal fitthat can be used as a replacement for all VRO equipped motors and each partis available for servicing.When working on a customer's fuel system, check for any restrictions or airleaks which would affect the engine. You can use a clear piece of fuel lineconnected to the VRO inlet and "Tee'd" off to a vacuum gauge. Run the motorat all speeds while inspecting for air bubbles in the line and for anyvacuum restrictions above 4" Hg. A system with 3/8" fuel lines, a clean"spin on" filter, and a quality anti-siphon valve should show between 2.5"to 3" of vacuum at full speed.Doing a thorough job the first time avoids expensive and sometimes highlyemotional "comebacks", keeps the customer happy, and makes your reputationthe best advertising there is.

[DTro]

I had the same motor. Pump failed.....scorched cylinder(s). Now whether or not it was the VRO or something else. I DO know this, there was plenty of oil in the tank and yet it still fried. That wouldn't have happened if I was premixing.

I guess if it's worth that much to not have to mix your gas, well then yeah I see no reason either. This has been discussed quite often, and my view is that it's worth the piece of mind to take a few minutes to mix my own.

I don't have the motor any more, but to answer the original question, all I did was disconnect the oil side of the pump, plug it with a screw, and then disconnect the warning alarm wire.

[PierBridge]

By all means if it makes you feel safer switch over to pre-mix.

Pretty rare for the VRO2 "not vro" pump and the "no oil flow" alarm to fail at the same time again this is for post 1985 VRO2 systems not the dreaded early vro systems.

[Valv]

... and you want me to read that ???

[Eric Wettschreck]

Ok, so now for my next dilema. I managed to repair all the leaks on this VRO(2) pump.

Now, my motor runs terrible. Very boggy. Not so much at idle but absolutely no power under load. The primer bulb will not stay pressurized. When I pump the bulb I can see the fuel enter the little plastic "Chamber" prior to the VRO(2) pump. As the motor runs, the level in the "Chamber" drops until empty, then motor dies. If I continue to pump the bulb, the motor runs fine.

Did my VRO(2) pump just die on me?

[Valv]

How did you manage to repair the leaks ? Fuel pump is a standard diaphragm type, if any of he thin rubbers is bad or has a small hole you will have to rebuild it.

The kit is not very expensive at all

[Eric Wettschreck]

Valv, it turns out it wasn't the pump itself that was leaking but many of the fuel lines coming off of it. With fuel dripping all over the place it appeared it was the pump, but I was wrong.

Do the symptoms I described sound to you like the VRO(2) pump is bad?

[boatfixer]

If you are certain you fixed ALL the leaks, then yes, it does sound like it is bad.

[Valv]

Quote:

---

Valv, it turns out it wasn't the pump itself that was leaking but many of the fuel lines coming off of it. With fuel dripping all over the place it appeared it was the pump, but I was wrong.

---

Shhhh... !!! Don't say that or we have to admit PierBridge was right, I really don't want to....

[solbes]

First of all, interesting topic since I run an '84 Evinrude 90. Every year I cross my fingers that the VRO doesn't die on me. Hope it last 3 more years when I will finally get a new boat.

I have little boat repair experience, but couldn't your problem just be a bad check valve in your primer?

[Eric Wettschreck]

I could be that.

The fuel line and primer will stay pressurized until I start the motor. I don't have a lot of experience with these types of fuel systems myself. Therefore I brought it up on this fourm.

[upnorth]

I had a similar problem on my 87 70 evinrude, the bulb was pointing down and the check valve would not release. Also be sure you have the fuel flowing through the bulb in the right direction.

By the way the VRO pump also acts as the fuel pump so you can't remove it, you would have to plug the oil feed side and find out how to disable the alarms if you want to mix oil manually.

[goose52]

i have a 70hp 1990 evinrude. about 5 years ago oil alarm started going off all the time. i had alarm disconnected and just mix oil in gas now, with no problems. oil pump still hooked up. before this i use to add some oil to gas (100-1) just in case of oil pump failure. service guy recommended years ago, as a number of motors had fried.

[Eric Wettschreck]

Well, I'm back to working on this motor.

Valv, Pierbridge, anyone.......I've been looking on HSOList for a new or rebuilt VRO (2) pump. How do I know the which model # to get? Many of them look alike. It's an 87, 70 hp. There is no model # on the pump itself and my shop manual really doesn't do a very good job of explaining anything.

Appreciate everyones help.

[boatfixer]

Boilerguy-I hope this is helpful.

DISTINGUISHING VRO's

Of all the traditional two stroke outboards produced worldwide, OMC products have the only automatic lubrication systems with a "no oil flow" alarm. The VRO's electronic circuitry compares the RPM of the engine to the number of pressure pulses from the oil pump piston. As the oil flows into the fuel area, the pressure moves a small piston that actuates a steel pin in the alarm module. The pin's movement is detected electronically and "counted." If the engine revolutions exceed the preprogrammed oil pulse ratios, the warning horn is activated sounding a rapid on and off sequence. Since 1993, the VRO is actually called an oil metering system (OMS). The ratio averages about 60:1, slightly leaner at idle and slightly richer at full throttle. The older pumps idled between 150:1 (prior to 1990) and 100:1 (1990-1992), then richened up to 50:1 as the engine load increased. They are recognized by the brown fuel outlet fitting and/or a wiring harness attached to the alarm module.

The original VRO from 1984 and 1985 had a black fuel outlet fitting and no wiring. OMS pumps have a blue/gray outlet nipple or a blue/gray pulse nipple, or a black fitting held in place by an oval metal bracket and two Torx headed screws. To simplify things just remember that the air motor converts the crankcase pulses to a back and forth motion. Directly connected to the air motor is the fuel pump and the oil pump. The travel of the air motor pumps the fuel and the oil together to the carburetors and the alarm system monitors the oil pressure counts. Just like manually premixing the oil and gas, the VRO (OMS) automatically does the same thing and sends that fuel mixture to the carburetors

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[JohnMickish]

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