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Author Topic:   What An Improvement (Removal of VRO pump)
Sal DiMercurio posted 11-24-2006 07:16 PM ET (US)   Profile for Sal DiMercurio   Send Email to Sal DiMercurio  
Through the years I've had quite a few diffent engines and my dad had a 70 hp Johnson 3 cylinder and it kinda ran rough at idle and I thought it was the nature of the beast. Now I own a 1997 - 70 hp Johnson that also ran kinda rough at idle even when my buddy owned it. I had the engine rebuilt by Blackbir--he scored a cylinder--and it ran better than when my buddy owned it, but still rough and too fast at idle. I noticed to much smoke the last couple times out and the engine was just stumbling all over it self while trolling. I got home and cut the oil line and put a 5/16-bolt in both ends of the oil line, reached up on top of the engine and disconnected the 4 VRO wires and added 3 pints of XD50 Evinrude oil to my 18 gallon tank and filled it with gas. Went trolling and it ran smoother but after about 40 minutes of trolling she died and it sounded like she ran out of fuel, so I pumped the fuel bulb and it started right up again and ran fine for another 1/2 hour until I gave it some throttle to move to another area and she started to slow down like she was running out of fuel. I again gave the bulb a couple of pumps and she was fine. It was than that I said to myself, OK, I'm going to remove the fuel oil pump and do away with the VRO and just mix my own oil and install a new fuel pump.

In case your interested a fuel oil VRO pump is $400 and a straight fuel pump is $35 so I removed the big unit and installed a straight fuel pump.

Took her out this morning and she finally idles at 800 rpms and she runs smooth as glass. This engine as long as I've known it has always run "VERY" rough at troll speed and even after the rebuild, she was better when I disconnected the VRO but still kinda rough and idled at 1000 - 1200 rpms no matter how much I adjusted it, until I replaced the fuel oil pump. Now she idles at 800 rpms smooth as smooth can get. I could fill a glass of water to the rim, start the engine , put her in gear and troll with the glass of water on top of it and not spill even one drop. All this time it was the damn fuel oil pump. Absolutly "NO" smoke and excellent performance while trolling, cruising, and WOT.

Just some food for thought in case any of you 3 cylinder Johnson guys are interested.

Binkie posted 11-24-2006 07:26 PM ET (US)     Profile for Binkie  Send Email to Binkie     
If only outboards never evolved past the early `80`s, boating would be a lot simpler.


Sal DiMercurio posted 11-24-2006 08:51 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Binkie, basicly this particular engine hasen't changed from the early 80s until about 1998 with the exception of the VRO in about 1986. The powerhead I think is the same with minor improvments.
contender posted 11-24-2006 09:18 PM ET (US)     Profile for contender  Send Email to contender     
I bought a new motor(evinrude 140 looper in 1985) with the VRO, the VRO was not connected from the factory. I rigged my 17 and started to look where to place the oil tank and lines. I then read the factory service card and it stated that the vro was not required and did not void the warr. I figured more things to go wrong, more wasted space. I disconnected the oil pump from the engine and toss it in the trash with the tank, lines, and bracket. I still have this engine today(mixing the oil and gas) and it runs great. Good luck
where2 posted 11-24-2006 10:13 PM ET (US)     Profile for where2  Send Email to where2     
Contrary to popular belief, you can get replacement diaphragms for the VRO fuel pumps for less than the $400 replacement pump cost. The trick is to be able to judge whether the seal between the two portions of the pump is shot or not. If the seal between the two portions of the pump is shot, you either get a new VRO pump, or you go the route Sal went with the Non-VRO pump.

My 1985 70Hp Johnson (on my 15_Sport) has been running premix fuel since I bought it in 1996 from the original owner (with the oil line pluged). My 1995 15_Rage is running it's VRO in perfect order. (The 15_Rage has plenty of room for the oil tank to live peacefully out of the way, the 15_Sport has no room for extra stuff).

Glad to hear you've been out enjoying the boat Sal...

Sal DiMercurio posted 11-24-2006 11:15 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Since the rebuild I've put 46 hours on this engine, & it's my belief this was the problem all the time & caused that middle cylinder to run lean & score when my buddy owned it.
It had less than 350 hours on it when it scored.
PeteB88 posted 11-25-2006 12:32 AM ET (US)     Profile for PeteB88  Send Email to PeteB88     
Reading all this makes sense and causes me to continue to wonder if same could be the case with my 1992 Yamaha 40 3-cylinder Precision Blend. It runs rough as far as I'm concerned and smokes way too much and the plugs seem dark or oily. Rough running seems to be low rpms and 50% to full throttle it smooths out - especially WOT. I bought Selock and Clymer manuals for my motor (range of years) and neither one is clear regarding adjustments for my motor which is really frustrating. Both reference timing, carb, linkage, and oil injection adjustments but photos, diagrams and instructions are not clear enough for me to dive in - including carb rebuild.

I want to do things myself as opposed to taking to a mechanic because I want to learn how to take care of my equipment. But not sure I can do it this time.

Perhaps I should disconnect the injection system but people I talk to say it's the best there is. I am interested in more discussion on this topic especially specific stuff about Yamaha.


jimh posted 11-25-2006 09:47 AM ET (US)     Profile for jimh  Send Email to jimh     
The results of Sal's experiment point to the conclusion that his VRO pump was causing poor low-speed performance, but they do not provide proof that all engines run better on pre-mix than they would with a VRO pump which was operating properly. To really test that theory you'd have to install a new VRO pump and see how Sal's engine ran when its VRO system was working as it was designed.

The acronym VRO is for Variable Ratio Oiling, and the design goal was to reduce the oil/fuel ratio to around 1:100 at idle. This would imply that the engine ought to run more smoothly and be less prone to plug fouling because there was less oil in the fuel.

The latest versions of the VRO, now called the OMS for Oil Metering System or perhaps Oil Mixing System, do NOT vary the oil ratio over as great a range as in prior versions. There are no adjustments for the OMC VRO system.

Sal DiMercurio posted 11-25-2006 09:07 PM ET (US)     Profile for Sal DiMercurio  Send Email to Sal DiMercurio     
Jim, the VRO was pumping to much oil & loading up the engine but the fuel pump was the culprit that made the engine run so rough.
After I cut the oil line & pluged it & un-pluged the wires for it, the engine ran better because it wasen't being drown with oil but it still ran rough up to 2000 rpms, "BUT" the darn fuel pump was the culprit that made the engine run so rough.
As soon as I removed the fuel pump [ 3 hours after running it & removing the VRO pump ] the engine ran smooth as glass.
Personally I think the fuel pump was faulty right from the factory because this engine ran rough from the day he bought it.
I really believe the fuel pump starved that middle cylinder to the point that it scored & had to be re-built & had I not changed the fuel pump, it could very well score again from running to lean.
I do believe the over active VRO pump contributed to the rough running but it sure smoothed out after changing the fuel pump.
nnylip posted 11-27-2006 09:14 AM ET (US)     Profile for nnylip  Send Email to nnylip     
I have a '91 70hp evin on the back of my 15 super sport. My mechanic recommended disconnecting the VRO in the summer of '05, because of smoking, tough starts, quits. It ran poorly that whole summer and over the '05/'06 winter, he rebuilt the carb, new plugs, linkage adjustment, etc. This summer its run the best its ever run, low speed and high speed. However, one of my uses is tubing (urgh!) which means I spend some time sitting in the back with the idling engine while everyone else screws around with ropes, tube, getting in and out of the tube / boat etc. In this scenario, the engine, with the disconnected VRO, definitely smokes more (which I inhale more than I would like, given the situation) than the engine with the connected VRO connected and semi working properly. Net / net, my boat is better off with the mods described earlier, but my experience would indicate that there is more low speed smoking with the VRO disconnected (which I assume should be expected). - Lou
brisboats posted 11-27-2006 09:38 AM ET (US)     Profile for brisboats  Send Email to brisboats     
Yep the VRO will smoke less at idle as it vaires the mixture rate from something like 200:1 to 50:1 depending on throttle opening and whether you have VRO 1 or 2 blah blah.

What we did with one of our crabbing skiffs was rig a poorman's vro. One tank rigged at 100:1 for idling, running the trot line and attending to pots and one rigged at 50:1 for the runs out and in. Simple works great and less oil use and smoke at low speed. A brass Y valve and you don't even need to switch tanks. Ingenious like the original VRO? No, but it works all the time and well we just can't say that about the original system.


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