Sorry if this is a dumb question - 100 HP 92 Merc 4 Cylinder

[-Jim-]

Gents,

Sorry if this is a stupid question but my Brother who sold me his old boat (and I'm taking it out for the first time on Thursday) was saying the specifications are the same for the 90 & 100 & 115 HP versions of this motor. He suggested there was some "electronic" wizardry that gave more output.

I suggested it was more than likely Carburation changes between ratings. But I really have little to base that on => either way => and I can't find anything.

Perhaps you know what's the real truth.:redface:

Thanks for the assist.

 

[Faztbullet]

Re: Sorry if this is a dumb question - 100 HP 92 Merc 4 Cylinder

The 4 cylinder engines(100/115/125) from 1994 and up use the same powerhead the only difference is carbs. Your year model(92) the 100/115 is the same engine.

 

[-Jim-]

Re: Sorry if this is a dumb question - 100 HP 92 Merc 4 Cylinder

The 4 cylinder engines(100/115/125) from 1994 and up use the same powerhead the only difference is carbs. Your year model(92) the 100/115 is the same engine.

Faztbullet, thanks for the info.

Now I'm intrigued. Do 1994 125 HP Carbs fit easily onto a 1992 100 HP? If so is that the only change to get a 25 HP increase?

 

[-Jim-]

Re: Sorry if this is a dumb question - 100 HP 92 Merc 4 Cylinder

Folks,

If Faztbullet doesn't know can you advise?

Thanks.

 

[CharlieB]

Re: Sorry if this is a dumb question - 100 HP 92 Merc 4 Cylinder

Yes, it is just the carbs,

BUT.....

You MUST get the carbs in the correct order as the jetting on 1, 2, 3, & 4 are NOT the same, get then in the wrong order and you can toast a cyl.

Check the parts diagrams/list at

http://www.mercruiserparts.com/mercruiser_parts.asp

your serial # may be found in the Merc/Mariner pages as that motor was available under both brands.

The parts list should show the different carbs for each HP model that was available on that same base engine.

If youo clean your carbs pay particular attention to the main jet sizes and which jet is in which carb and you will see the difference. Do NOT switch the jets around.

 

[-Jim-]

Re: Sorry if this is a dumb question - 100 HP 92 Merc 4 Cylinder

Thanks for the info and link but I'm struggling how to use the info. My Serial is OD129908 and I find it under Merc/Mariner like you suggested. But I'm missing the point where to go from there. I assume the Carbs must be changed out completely to 125 HP Carbs, or is it simply a matter of changing Jets or other parts of the Carbs out (sorry if my ignorance is showing too much:redface.

Yes, it is just the carbs,

BUT.....

You MUST get the carbs in the correct order as the jetting on 1, 2, 3, & 4 are NOT the same, get then in the wrong order and you can toast a cyl.

Check the parts diagrams/list at

http://www.mercruiserparts.com/mercruiser_parts.asp

your serial # may be found in the Merc/Mariner pages as that motor was available under both brands.

The parts list should show the different carbs for each HP model that was available on that same base engine.

If youo clean your carbs pay particular attention to the main jet sizes and which jet is in which carb and you will see the difference. Do NOT switch the jets around.

 

[Faztbullet]

Re: Sorry if this is a dumb question - 100 HP 92 Merc 4 Cylinder

You must change the complete carb body and jets....

 

[-Jim-]

Re: Sorry if this is a dumb question - 100 HP 92 Merc 4 Cylinder

You must change the complete carb body and jets....

Thanks that's what i thought. So I guess the question is how do you determine what 125HP Carbs are a fit to my engine?
Any suggestions?

Thanks.

 

[Dave1027]

Re: Sorry if this is a dumb question - 100 HP 92 Merc 4 Cylinder

You MUST get the carbs in the correct order as the jetting on 1, 2, 3, & 4 are NOT the same, get then in the wrong order and you can toast a cyl.

Why is the jetting different per carb? My manual says the jetting for a '88 100 hp is .054 inch on all carbs. Was it changed at some point?

 

[Dave1027]

Re: Sorry if this is a dumb question - 100 HP 92 Merc 4 Cylinder

Thanks that's what i thought. So I guess the question is how do you determine what 150HP Carbs are a fit to my engine?
Any suggestions?

Thanks.

Jim, the max hp for that engine was 125, not 150. Where did you get 150 from?

 

[-Jim-]

Re: Sorry if this is a dumb question - 100 HP 92 Merc 4 Cylinder

Jim, the max hp for that engine was 125, not 150. Where did you get 150 from?

Sorry, my goof. (maybe wishful thinking ) I edited it to 125 HP. Thanks.

 

[-Jim-]

Re: Sorry if this is a dumb question - 100 HP 92 Merc 4 Cylinder

Thanks that's what i thought. So I guess the question is how do you determine what 125HP Carbs are a fit to my engine?
Any suggestions?

Thanks.

Has anyone here ever done this? :redface: