1998 force 40 hp

[gcjames]

I have a 1998 force 40 hp and i have been doing some checking i have cross referenced the part numbers on the powerhead and it is the same as the 50 force of the same year as far as i can tell everypart of the motors are the same except for the main jet in the carb. the 50 has a .96 jet and the 40 has a .62 jet. Both are geared 2.0:1 and both weights are the same. Mercury part number for the powerhead is the same. Are there more differences? Oh ya full throttle RPM range is the same 4750-5250. How does more fuel without more rpms = 10 more horse power.

 

[12Footer]

Re: 1998 force 40 hp

Pre97 Force is rated at the powerhead,later models rated at the prop. This is the only difference I was aware of, but won't argue with the book.

 

[gcjames]

Re: 1998 force 40 hp

talked with local boat mechanic he said that the part that i am talking about int the carb. described as (MAIN JET) in the parts book will not let more fuel in into the engine it will only allow more into the carb. bowl ithought that would be described as the needle valve and seat? I have only worked on cars,motorcycles,lawnmowers,weedeaters and tractors. Does the main jet on a 2 cycle outboard not feed the engine?

 

[12Footer]

Re: 1998 force 40 hp

You are right. The main jet is on the side of the pickup tube. The needle valve and seat are where the fuel enters the carb,and will allow a larger jet size.

 

[gcjames]

Re: 1998 force 40 hp

thanks 12footer will be doing hands on research this friday with the jet to see if the tach or speed odmeter can tell the differnce

 

[Baucom84]

Re: 1998 force 40 hp

hey i have a 40 force was wonderin how ur projest is comin along might do the same

 

[sweezy722]

Re: 1998 force 40 hp

Guys you are wasting your time. I know from experience. You are correct with the fact that all parts are the same for 40 and 50 hp motors except the main jet in the carb. The 40 takes the .062 while the 50 takes .096. The larger main jet will allow much more fuel in the motor, so much more that it will choke it down and barely run above idle. The 50hp block must be ported different to allow more air flow and proper combustion of the extra gas.

Yes I have a new jet .096 in my tool box only used for 90 seconds. Itwill not work.

 

[foodfisher]

Re: 1998 force 40 hp

Don't know jetting but logic tells me a little more gas=alittle bigger bang. Within limits of course.

 

[sweezy722]

Re: 1998 force 40 hp

The 50hp jet of .096 is 155% larger than the jet for the 40hp .062. There are no small differences there. You only get the bigger bang if the motor will consume the extra air to make the bigger bang. I do not think the 40hp is ported to consume the extra air. To burn 1 gallon of gas the average internal combustion engine consumes around 9000 gallons of air. Extra gas without the air equals flooding and fouling with deposits to jack the rings and score the walls.