1992 johnson 90hp V4

[haneybear]

I have a 1993 Nitro bass boat with a 90 hp that I purchased in 1995 and in looking thrun the motor manual thst came with the boat I see that all the components ar the same if it is a 90 hp or the 115 hp.I have been to 3 local OMC dealers to see what I would have to do to make this motor a 115hp.All have told me no problem just leave it and for X-dollars they can take care of it.I would like to find out if anyone knows the majic formula to converting to the higher HP. the motor is a 1992 90/115 TL,motor serial number 03198865,Model number T 190ET.Any help or information would be greatly appreciated,I would like to know if this is something that I can do myself of is this strickly a dealer retrofit

 

[BKool68]

Re: 1992 johnson 90hp V4

One quick change is the exhaust manifold from your flat to a bubbled exhaust.

 

[haneybear]

Re: 1992 johnson 90hp V4

I am not fimilar with this bubble exhaust can you be a little more specific on what this is and is this something that I can get from the dealer or is this an aftermarket item thanks for the quick reply dave

 

[JB]

Re: 1992 johnson 90hp V4

Howdy, Haneybear.<br /><br />Don't bother. You wont get your money worth in improved performance and the complete conversion is complicated and much too expensive.<br /><br />

 

[Dhadley]

Re: 1992 johnson 90hp V4

The "bubbled" (tuned) exhaust will help some but only if you are able to achieve the higher end of the RPM scale now. To complete the transition you would need to open the intake and exhaust ports to the 115 (older 140) sizes. Very easy if the motor is apart.<br /><br />If you can't turn the motor 5800+ now, don't worry about it. As JB says, it wont do anything.<br /><br />If you want to you can list your top RPM, TRUE current speed and prop size and we can calculate % of slip now. There might be room for improvement. <br /><br />Good luck!