115 vs 125 hp merc conversion?

[nbpbborg]

anyone know if and how a 1992 115hp merc can be converted to a 125 hp merc? Same CID, is it carb jetting or port timing, or both?

 

[corm]

Re: 115 vs 125 hp merc conversion?

Hi Nbpbborg,<br />Nope it can't. the 92 115 is 105 cu in.<br />the 125 started in 1994 at 113 cu in.

 

[nbpbborg]

Re: 115 vs 125 hp merc conversion?

Corm, I guess that was my mistake. I was told by my mechanic that my 115 was a 113 cu in. How'd they get the extra cubes? Interesting also, becuse the 2001 115 hp's are 113 cu in also....what is going on??

 

[corm]

Re: 115 vs 125 hp merc conversion?

In 1994 Merc did a major redsign on those motors. They could not get 125Hp from the 103 cu in block. So they upped the cu in. just like they did on the 75 & 90, which was done to hlp move the heavy boat they were being put on to keep the price down. They went from 71 to 84 cu in.<br />The 100&115 have a different gear ratio than <br />the 125 also. They bored the block from 3.38<br />to 3.50. The stroke is the same on the 75 to 125 HP motors. I don't know off hand if they changed the port timing on the 125, but could check if you need to know.<br /><br /><br />------------------<br />...have fun...corm<br /><br />cubic inches = power<br />power = speed<br />speed = FUN<br /><br />Email me if you need to.

 

[Mozart]

Re: 115 vs 125 hp merc conversion?

Johnson also had a similar motor 115/125 hp - they achieved the difference via different jets and tuned (and polished) intake and exhaust ports/manifolds. as per my mechnic. However, in his experience, the cost involved was not worth trying to up the lower hp to the upper hp as he could not tell the difference (maybe they didn't actually obtain 125 hp?)