How do I convert my 75HP Mercury from oi injection to premix?

thekozz

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Mar 24, 2012
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1
Hi,
I have a 75HP Mecury. I want to covert it from oil injection to premix. Is there a kit or does anyone know of a procedure that I can perform? I believe that it is a 88 motor. Any information will be greatly appreciated.
 

Bondo

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Apr 17, 2002
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Re: How do I convert my 75HP Mercury from oi injection to premix?

Hi,
I have a 75HP Mecury. I want to covert it from oil injection to premix. Is there a kit or does anyone know of a procedure that I can perform? I believe that it is a 88 motor. Any information will be greatly appreciated.

Ayuh,.... Just don't put oil in the tank,..??

Movin' to the Merc outboard forum...
 

Laddies

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Sep 10, 2004
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Re: How do I convert my 75HP Mercury from oi injection to premix?

Remove the pump and remove the driveshaft for the pump then reinstall the pump, to keep the pump and drive from self destructing
 

Texasmark

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Dec 20, 2005
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Re: How do I convert my 75HP Mercury from oi injection to premix?

Remove the pump and remove the driveshaft for the pump then reinstall the pump, to keep the pump and drive from self destructing

Laddies sir, I did this recently on my 3 cyl 90. All that I removed was the ss drive gear which was part of a shaft with a slot in the other end for running the pump. Somebody on here said that I had to remove something else at the gear end of the shaft, like a stop to keep the shaft pushed up against the pump, keeping the slot engaged. I looked at my IPB and saw no other part. Did I miss something?

Thanks,
Mark
 

Laddies

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Re: How do I convert my 75HP Mercury from oi injection to premix?

No, removing the shaft and gear is all you need to do.
 

Bobv

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Jan 22, 2009
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Re: How do I convert my 75HP Mercury from oi injection to premix?

Laddies sir, I did this recently on my 3 cyl 90. All that I removed was the ss drive gear which was part of a shaft with a slot in the other end for running the pump. Somebody on here said that I had to remove something else at the gear end of the shaft, like a stop to keep the shaft pushed up against the pump, keeping the slot engaged. I looked at my IPB and saw no other part. Did I miss something?

Thanks,
Mark

Any problems since you did this? I'm doing the same to my 88 75hp. Thanks
 

Texasmark

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14,544
Re: How do I convert my 75HP Mercury from oi injection to premix?

Any problems since you did this? I'm doing the same to my 88 75hp. Thanks

None other than a tad more smoke at idle, but I use synthetic blend oil so the smoke isn't that bad anyway. However........I did write on my boat adjacent to the fill plug: Add 1 pt of oil to 6 gallons of gas just so I wouldn't forget. Years and years ago premix is all you had so you became accustomed to it. Then 5 years ago I buy this automix engine and all I do is put gas in the tank. So, I have to remind myself to add the oil.

Mark
 

Bobv

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Jan 22, 2009
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Re: How do I convert my 75HP Mercury from oi injection to premix?

Thanks for your input, I've been trying to find out how to do this for a while now.
 

1nebel0

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Nov 28, 2005
Messages
512
Re: How do I convert my 75HP Mercury from oi injection to premix?

Thanks for your input, I've been trying to find out how to do this for a while now.

Here is another twist I did... I have a 90h.p basiclly the same motor...I took the hose coming off the oil pump drilled a hole in the tank at the top, put a grommet in and put the hose in there... I am using the oil that is in the tank as it recycles itself through the oil pump and then back into the tank..This way everything is right there is someone buys the boat-which they are doing now and can make up their own mind...The large engines have a plug that replaces the pump to hold the plastic drive gear on the crank in place. Wished they made them for all of the motors...Anyway, Laddies is the expert, I just cheated....
 

Bobv

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Jan 22, 2009
Messages
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Re: How do I convert my 75HP Mercury from oi injection to premix?

Here is another twist I did... I have a 90h.p basiclly the same motor...I took the hose coming off the oil pump drilled a hole in the tank at the top, put a grommet in and put the hose in there... I am using the oil that is in the tank as it recycles itself through the oil pump and then back into the tank..This way everything is right there is someone buys the boat-which they are doing now and can make up their own mind...The large engines have a plug that replaces the pump to hold the plastic drive gear on the crank in place. Wished they made them for all of the motors...Anyway, Laddies is the expert, I just cheated....

How did you block off the input to the fuel pump where you removed the hose?
 

Bobv

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Jan 22, 2009
Messages
11
Re: How do I convert my 75HP Mercury from oi injection to premix?

Laddies sir, I did this recently on my 3 cyl 90. All that I removed was the ss drive gear which was part of a shaft with a slot in the other end for running the pump. Somebody on here said that I had to remove something else at the gear end of the shaft, like a stop to keep the shaft pushed up against the pump, keeping the slot engaged. I looked at my IPB and saw no other part. Did I miss something?

Thanks,
Mark

I've got the pump off but the shaft w/gear doesn't want to come out. Am I missing something? Thanks Bob
 

Bobv

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Joined
Jan 22, 2009
Messages
11
Re: How do I convert my 75HP Mercury from oi injection to premix?

Answered my own question. There is a block (oil pump adapter assembly) that stayed on the engine when I removed the pump, it needs to come off and the shaft comes with it. All good. Bob
 

davem1901

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Sep 9, 2012
Messages
1
Re: How do I convert my 75HP Mercury from oi injection to premix?

Here is another twist I did... I have a 90h.p basiclly the same motor...I took the hose coming off the oil pump drilled a hole in the tank at the top, put a grommet in and put the hose in there... I am using the oil that is in the tank as it recycles itself through the oil pump and then back into the tank..This way everything is right there is someone buys the boat-which they are doing now and can make up their own mind...The large engines have a plug that replaces the pump to hold the plastic drive gear on the crank in place. Wished they made them for all of the motors...Anyway, Laddies is the expert, I just cheated....

I have same question as Bobv. I like your solution as it keeps the pump working but you avoid relying on it to service your engine. Sounds like a winning idea. I am new to this sort of thing, but it looks like from the diagramoilpumptracker75.jpg you should be able to just replace the molded fuel line (part 25) with a straight fuel line. No oil to the gas but is recycled to the tank. Easy conversion back if someone wants to.

Comments on this would sure be welcome.
 
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