Can I swap 25HP Johnson with 50HP Mercury?

NeedMorePower

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Apr 8, 2008
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I'm new to the boating world and to outboard motors. I have a 1991 Lowe 1620 boat with a Johnson 25 HP outboard that came as a package when it was new. The boat is rated for up to a 60HP motor. The motor has remote steering and electric start. The throttle control / shifter is mounted on the right side (not sure what it's called). The fuel/oil is mixed manually.

Would it be difficult to replace this motor with a 1995 Mercury 50HP? The Mercury is currently installed on a pontoon boat and has a remote oil tank. I'm going to look at it this coming weekend but I'm not sure how many components would need to be replaced to make this work.

Thanks in advance for any advice you can provide.
 

JB

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Mar 25, 2001
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45,907
Re: Can I swap 25HP Johnson with 50HP Mercury?

Howdy, NMP

Welcome to iboats. :)

You will need to swap the controls and wiring harness as well as the engines.
 

steelespike

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Apr 26, 2002
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19,069
Re: Can I swap 25HP Johnson with 50HP Mercury?

Not an expert but you will have to change over everything with the Merc.
You need to be sure it is the same shaft length as the 25.15" or 20".
Merc will need a prop change.I'm guessing it now has a 9 or 10 in. pitch. for
the pontoon. Try to find some place to let you test props.My guess is start with a 15" pitch to test.Fine tune the verticle height and trim raise it to just before venting becomes a problem.Then get us the max rpm and speed,typical load and the experts can get your final setup.Prop and final rpm is important for the health of your motor.
 

NeedMorePower

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Re: Can I swap 25HP Johnson with 50HP Mercury?

Thanks for the quick replies! It sounds like it will be more difficult than I had hoped. Maybe I should try to find a larger Johnson or Evinrude to make it easier?
 

HighTrim

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Jun 21, 2007
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Re: Can I swap 25HP Johnson with 50HP Mercury?

That will save you from swapping the controls and wiring harness.
 

Gary H NC

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Dec 1, 2005
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Re: Can I swap 25HP Johnson with 50HP Mercury?

That will save you from swapping the controls and wiring harness.
Thats for sure! It will save you a bunch of work.
That and a Johnny Rude is a better motor...:p OOPS! did i say that?:D
 

HighTrim

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Jun 21, 2007
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10,486
Re: Can I swap 25HP Johnson with 50HP Mercury?

Thats for sure! It will save you a bunch of work.
That and a Johnny Rude is a better motor...:p OOPS! did i say that?:D

SHHHHHHH......The guys next door in the Merc forum will hear you! :)
 

patrick4266

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Nov 29, 2007
Messages
591
Re: Can I swap 25HP Johnson with 50HP Mercury?

I myself have heard the jonny rudes are better motors. is it really true?
 
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