Change a VRO to manual mix 1990 70 hp johnson.

daveydoodle

Petty Officer 2nd Class
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Jun 15, 2011
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160
I don't trust the VRO , I just bought the rig and want to change over. Bought the new pump with plans on having it done at an established dealer but no go-they wont work on older than 96 in my area. Trying it myself but have some questions. The new pump has two brass hose fittings for gas I assume, the dealer said make sure you connect the pulse tube- pointed to the last of the three connections- a blk. plastic connector fitting with an arrow pointing downward. All I see under the cowling is a tube on port side that says vro. Is this new pump installed in the area of this piece? The new pump has two bolt holes. seems like an easy bolt on and connect the gas lines - sounds somewhat simple? Think there should be some elec. components to de activate the warning buzzer too. Any advice appreciated... Davey OHH and am I at 50-1 or 100-1 mix with the new pump??
 

oldboat1

Fleet Admiral
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Apr 3, 2002
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9,612
Why not use the existing fuel pump (i.e., fuel pump that is part of the existing system)? Plug off the oil line at the pump, and disconnect the wire harness. Premix in your gas tank (50:1) and go boating, yes? If the existing fuel pump fails, you can always substitute the new pump.
 

daveydoodle

Petty Officer 2nd Class
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Jun 15, 2011
Messages
160
Oldboat, makes sense to me. I had this done a few yrs back on a pontoon w/ a 50 evinrude. I was told by the same guy I'm waiting on now it requires a new pump so I went with it. That one never ran better. I'm far from an expert on this topic but Ill check in to that. From what you say there should be a wiring harness on or near the pump for the warning buzzer indicating no oil to the engine. Would the disconnect effect the overheat on the buzzer since that is the only warning function remaining to be concerned with?? And if you know where the heck is this pump/vro located on the motor?
 

oldboat1

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Apr 3, 2002
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9,612
Think you remain OK on the overheat alarm. Check by grounding the tan wire, key on -- horn should sound.
 

Joe Reeves

Supreme Mariner
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Feb 24, 2002
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13,262
(VRO Changeover Judgement Call)
(J. Reeves)

The VROs first came out in 1984 and have been upgraded quite a few times. In my opinion, back around 1988, they had perfected them but I think that they were upgraded even more since then. As long as the warning system is operating as it should, I feel quite at ease with them.

Some boaters have voiced their thoughts such as "What if that overpriced plastic horn should fail while I'm under way for some reason, and the VRO decides to fail five minutes later?" Obviously that would result in a big problem which really brings their fears into view.

The word "ease" is the key word though. If one has the slightest feeling of being ill at ease with that setup, then they should take the route they feel more at ease with. A judgement call each individual would need to make on their own.
********************
(VRO Pump Conversion To Straight Fuel Pump)
(J. Reeves)

You can convert the VRO pump into a straight fuel pump, eliminating the oil tank and VRO pump warning system, but retain the overheat warning setup (and fuel restriction warning if so equipped) by doing the following:

1 - Cut and plug the oil line at the engine so that the oil side of the VRO pump will not draw air into its system. Trace the wires from the back of the VRO to its rubber plug (electrical plug) and disconnect it.

2 - Trace the two wires from the oil tank to the engine, disconnect those two wires, then remove them and the oil tank.

3 - Mix the 50/1 oil in the proper amount with whatever quantity fuel you have. Disconnect the fuel line at the engine. Pump the fuel primer bulb until fuel exits that hose with the tint of whatever oil you used. Reconnect the fuel hose.

That's it. If you want to test the heat warning system to ease your mind, have the key in the on position, then ground out the tan heat sensor wire that you'll find protruding from the cylinder head. The warning horn should sound off.
 

daveydoodle

Petty Officer 2nd Class
Joined
Jun 15, 2011
Messages
160
I think I'm doing this change over myself. The old salt mobil marine mech. said OMC requires 100-1 mix , most guys here and vids. are saying 50-1. I will say when the salt did my toon @ 100-1 it ran like new, was a 98 50 hp evinrude..I do have a 16 gallon built in tank that's nearly topped off , may even have to take a little out before the mix but please re-affirm your mix thoughts. Thanks, Davey
 

racerone

Supreme Mariner
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Dec 28, 2013
Messages
38,415
Motors will run very nice on 100:1 mix !!!----But not for as many hrs as at 50:1-----Posts like #7 are just more proof that lubrication inside a 2 stroke engine is not well understood.
 

cfauvel

Chief Petty Officer
Joined
Aug 16, 2005
Messages
645
The V in VRO meant Variable ...the early models had a ratio of 150:1 at idle, then 100:1 at idle then 80:1 at idle....but they ALL went to 50:1 at speed. from what I understand the OMS has an average ratio of 60:1....so just a tad leaner than doing premix. 50:1...

This assumes fresh diaphragms and springs....I can testify that as the springs wear and the diaphragms wear the ratio will actually go richer not leaner...
 

Joe Reeves

Supreme Mariner
Joined
Feb 24, 2002
Messages
13,262
I think I'm doing this change over myself. The old salt mobil marine mech. said OMC requires 100-1 mix , most guys here and vids. are saying 50-1. I will say when the salt did my toon @ 100-1 it ran like new, was a 98 50 hp evinrude..I do have a 16 gallon built in tank that's nearly topped off , may even have to take a little out before the mix but please re-affirm your mix thoughts. Thanks, Davey

The 100/1 mixture was a error inits making that was canceled via a bulletin released by OMC not too long after arrival on the marine scene due to warranty claims of many blown power-heads.

DO NOT even think of using a 100/1 mixture in your engine... stick with the safe proven 50/1 mixture.
 

cfauvel

Chief Petty Officer
Joined
Aug 16, 2005
Messages
645
^^^ yeah would NEVER think about running 100:1 pre-mix above 1000 rpm.....eeeeks
 

daveydoodle

Petty Officer 2nd Class
Joined
Jun 15, 2011
Messages
160
Right----- 50-1 is correct. runs great. movin on to the next task on the 1990. Thanks to all. BTW the vro was original , can be determined as original by the lack of a metal oval shape plate where the fuel in prong meets the body of the pump. This whole thing was a 1990 so I feel pretty good switching. 90 bucks vs. 500. Davey
 
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