115hp to 140hp Mod.

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mitchjenn17

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Jul 4, 2008
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20
Hello, needing info here! I have a 1978 Xflow 140 hp Johnson that has a bad cylinder, I recently purchased a 1985 115 hp Xflow powerhead to replace my 140 hp. I have been told by several people that with a modification to the 115 powerhead on the back I can use the "bubble" between the heads on the 140 on the 115 and the carbs off the 140 on the 115 and I would in turn have a 140 hp motor. Is this a fact? And can anyone tell me what the modification consists of and how much difference in power will there be in doing this modification to the 115 hp? Any info will be greatly appreciated.

Thanks.
 
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jason915

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Jun 16, 2009
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Re: 115hp to 140hp Mod.

I just posted the same question, well almost. I have a 78 115 that has been rebuilt and runs great but I can get a complete blown 78 140 power head that I would like to use the upgrades on my 115 for more HP. So the easy stuff to swap over is carbs, reeds, and cylinder heads. The bubble back exhaust from the 140 will work on the 115 block but you have to modify the block by removing some material, not sure how much or where. It seems like a common question, maybe someone on here that has actually done it can shed some insight on the procedure?
 
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mitchjenn17

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Joined
Jul 4, 2008
Messages
20
Re: 115hp to 140hp Mod.

Ok lets make this simpler. All im seeing is opinions LOL! Im needing facts please. Like others I cant just run out and buy a replacement motor, all I need is the basics for doing the swap. I have a 1983 17.5ft Hydrosports bass boat if that helps in evaluating this swap, but really I just need the basic info of the swap. I bought the 115hp with everything but the carbs is the reason for doing the change over. The 140 is an 1978 and the 115 is a 1985. Can I just bolt the 140 carbs to the 115 and go? If not and I have to change the reeds and other stuff then the complete swap over is more feasible. Can anyone give me a detailed outline of what i would have to do to do this change over? Not meaning to sound bitter and im not, I just wanna go fishing again before summer is over!:D
 
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