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Johnson VRO/fuel pump interchange

 
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JohnL



Joined: 09 Jan 2010
Posts: 3
Location: S C

PostPosted: Sat Jan 09, 2010 10:15 am    Post subject: Johnson VRO/fuel pump interchange Reply with quote

Hello, I have a 1989 Johnson GT150 (mod#J150STL) in which the VRO/fuel pump went south. First, I will be premixing my oil and will need a replacement unit to serve only as a fuel pump. A bought a new VRO/FP (ebay) that was manufactured for a 3 cylinder OMC ... hope it will interchange o.k. My decision to purchase the 3-cylinder pump was based on this ... my old pump (part #0174878) and the new pump (part #0174876) had 3 equivalent replace parts in common #'s 0438406,5004559 & 5007423. My hope is that if the V6 & 3cylinder pump can be replaced by the same equivalent parts could they not be replaced by each other? Long story short .. can a 6 cylinder pump be replaced by a 3cylinder pump to move premixed fuel only without damanaging the motor. Thanks
JohnL
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MikeW
Senior Member


Joined: 01 May 2006
Posts: 680

PostPosted: Tue Jan 12, 2010 4:23 pm    Post subject: Reply with quote

Hi John, no you can't use the smaller pump. It will not give you the correct fuel and oil supply for a V6 150 hp engine Cool
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JohnL



Joined: 09 Jan 2010
Posts: 3
Location: S C

PostPosted: Wed Jan 13, 2010 3:27 pm    Post subject: Re: Johnson VRO/fuel pump interchange Reply with quote

JohnL wrote:
Hello, I have a 1989 Johnson GT150 (mod#J150STL) in which the VRO/fuel pump went south. First, I will be premixing my oil and will need a replacement unit to serve only as a fuel pump. A bought a new VRO/FP (ebay) that was manufactured for a 3 cylinder OMC ... hope it will interchange o.k. My decision to purchase the 3-cylinder pump was based on this ... my old pump (part #0174878) and the new pump (part #0174876) had 3 equivalent replace parts in common #'s 0438406,5004559 & 5007423. My hope is that if the V6 & 3cylinder pump can be replaced by the same equivalent parts could they not be replaced by each other? Long story short .. can a 6 cylinder pump be replaced by a 3cylinder pump to move premixed fuel only without damanaging the motor. Thanks
JohnL


Mike,
Thanks for the response. What I am trying to accomplish is to pump premixed fuel ... so the oil pumping side of the VRO will be disconnected/nonfunctional. My big cocern is that I may not be able to pump the correct volume of fuel. What do you think. Thanks.

John
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MikeW
Senior Member


Joined: 01 May 2006
Posts: 680

PostPosted: Wed Jan 13, 2010 3:38 pm    Post subject: Reply with quote

I doubt it will pump enough. The only thing you can do is try it. As long as the fuel oil ratio is right you should be ok. You will know right away if the engine gets up to full speed. So, I would run it at full throttle for a minute or two and shut the ignition off. Pull the spark plug look at it to see if looks too lean is a bit wet. Cool
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JohnL



Joined: 09 Jan 2010
Posts: 3
Location: S C

PostPosted: Sat Jan 16, 2010 1:22 pm    Post subject: Johnson VRO/fuel pump interchange Reply with quote

Mike ... thanks for the advice ... I tried what you recommended ...
unfortunetly the fuel/oil mix in my tank is rich on the oil side ... anyhow the motor started and got up to speed o.k. ... I pulled the plug and it was wet. If I understood you correctly a wet plug is a indicator of a fuel/air ratio that is lean on fuel/too much air ... I would have guessed the opposite ... a dry plug would mean the engine is pulling too much air. I have been told not to run a motor with a lean mix can burn a hole in a piston. Is that right? Thanks.

John
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sleddinsteve



Joined: 18 Apr 2010
Posts: 2

PostPosted: Sun Apr 18, 2010 2:11 pm    Post subject: fuel pump mixtures Reply with quote

The fuel pump does not create a lean or rich fuel mixture. The pump simply fills the float bowl with fuel, thats it. The float needle and seat shuts the fuel off when the bowl is full. If your fuel pump is not large enough to fill the float bowl at full throttle operation, it will be running out of gas. You will know in just a short time if it is too small as your engine will start running out of fuel. It will most likely run fine at a lower rpm(but still depends on vacum created by the engine to operate the diaphram in the pump) depending on how much compression your engine has. Low compression = low vacum = low fuel pump suction. I would suggest the V-6 pump without the oil mix section, and buy the manual for references.
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