Remove VRO & Vacuum - 1991 150HP

Pat Crowley

Cadet
Joined
Oct 19, 2009
Messages
23
I have a 1991 Evinrude Nitro 150HP motor that I want to remove the VRO from and start mixing my gas. I have purchased 2 different books that are supposed to show everything for that motor but they don't. It seems like the 1991 was a one year wonder, or at least the VRO/Vacuum combination. Actually, I can easily remove the VRO part but, since it is married to the vacuum part, I'm not sure if the vacuum part is working or even needed. I have attached a pic of the VRO/Vacuum from my motor. Does anyone have an electrical diagram of this specific motor and does anyone have a vacuum hose routing diagram. I would appreciate any help/advice you can share.
 

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wilde1j

Vice Admiral
Joined
Apr 15, 2002
Messages
5,964
Re: Remove VRO & Vacuum - 1991 150HP

Have you looked at the sticky "Top Secret File"?

BTW, all VRO/fuel pump in the OMC world are vacuum operated. Typically, the VRO pump remains and is used to pump fuel only. An OEM shop manual would have a complete wiring diagram.
 

Joe Reeves

Supreme Mariner
Joined
Feb 24, 2002
Messages
13,262
Re: Remove VRO & Vacuum - 1991 150HP

(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.
 
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