1996 Force 120hp carb problems

[jph1996]

I have a 1996 120hp force that I have been having carb problems with. When starting a warm engine (no choke) I get gray smoke. At an idle the gas fumes are overwhelming, but idles smooth. As I throttle up from 1800-2400 rpm engine shakes and smell gas fumes. Above 2400 rpm engine runs really good and smooth. I have had it in the shop a few times to work on carbs, but they never actually fix anything. The carbs have been cleaned at the shop last trip in.

Is it possibly that the jets are the wrong size. I bought the boat used a few months ago, so I do not know what is actually in them. Compression on all four cylinders is still at factory specs about 170 psi. I don't think the engine has a lot of hours on it.

Any advice would be helpful.

Thank you,

Jeff

 

[pnwboat]

Re: 1996 Force 120hp carb problems

I believe standard jet size should be .094. You may not have a carb problem unless the needle valves are bad or floats are set too low. If the primer bulb gets nice and firm after squeezing 4 or 5 times then I doubt that's the problem. Idle mixture screw set too rich may cause it. They should be in the neighborhood of about 1 to 1 1/2 turn out from lightly seated. Make a note of the setting before you start messing with them though.

Fuel pump diaphragm may have a hole or leak in it causing excess fuel to be dumped into the engine too.

What kind of plugs do you have in it?

 

[jriegle04]

Re: 1996 Force 120hp carb problems

intermittent spark would cause this also. i would pull my psark plugs and give them a look to see what is happening in there. they always show signs of how well the engine is firing.

 

[jph1996]

Re: 1996 Force 120hp carb problems

The bayliner dealer here gave me autolite 2852 plugs. They have been replaced twice this year. Once when I bought the boat and again by the shop that worked on the carbs. The primer bulb does get hard after about 4 or 5 squeezes, but I have not checked if it actually maintains pressure. I don't know how old the fuel diaphragm is, that is probably a good place to start. The shop said the floats where adjusted correctly and did not need repair. All four plugs appear to be consistent with each other and look like I would expect for a 2 stroke motor. Don't really notice any engine missing just runs like it is always flooding with strong gas smell and great at higher rpm.

I friend with another boat was following me and said while idling and when throttling up I put out blue smoke and leave a gas smell behind.

I also found on the mercury site that the standard jets are for sea level to 1500 ft. The lakes around here are at 3000 ft level and above ( .092 or a .090 main jet ), but that is not much of a difference in volume.

Thanks, fuel diaphragm is cheap and does not appear to be hard to replace. Sounds like a good place for me to start.

Thanks.

-Jeff