Force 90 flooding

[joeboater]

Took my Force 90 in for some routine maintenance last winter (they adjusted the carbs & decarbonized the cylinders) and since then I have had a hard time starting it and it idles rough. Runs okay at open throttle positions. Was out this weekend and had to change the plugs to get it to start after I rested from a few hours of towing the tube around. The plugs looked fouled (black)and were wet with gas. I used a 50:1 premix from the lake's gas station and that really made things worse. How should I go about systematicaly troubleshooting this problem? Would it help to adjust the mixture screws or do I need carb work? Are these carbs easy to work on, and simple enough for a backyard mechanic? Help, anyone?

 

[12Footer]

Re: Force 90 flooding

I am asuming you are using new fuel.If the fuel is the same or "topped-off" from last season,this is your major problem with the engine. 2cycle fuel turns into varnish,sometimes within 1 month's time.<br />It does a number on carbs and fuel delivery systems. If this is old fuel, prperly dispose of it,and use fresh gas/oil mix.<br /><br />They are a simple carberator to work on. The Tillotsen (SP?) has been used since Force was Chrysler,and for good reasons.<br />It sounds to me like perhaps when the engine was "blown-out", it made a world of difference in the fuel flow, and if the carbs wern't re-adjusted properly after such a step, the mixture is probably way too rich.<br />There is a "window" of peak performance on outboards when it comes to fuel/air mixture.<br />Without getting technical, too much fuel mixed with the air,and you get the condition you are experiencing...Too rich.<br /><br />If you close them a half-turn,you should be ok. Turning it in too much,and the engine will stumble at high RPM, and a condition refered to here often as "fuel starvation" is created. This is bad news, as our 2cycle outboards have the lubrication mixed with the fuel....Not enough fuel,not enough lubrication,and the engine slowly self-destructs.<br />Turn the mixture in no more than a half-turn.<br />Install NEW,properly-gapped plugs,and see how it performs. If it still acts-up on you,take it a GOOD mechanic, to have the carbs set,that is, if the new plugs still foul on you. Once a plug fouls on you one time, it's time to replace them with new plugs. Outboard ignition systems are real firecrackers! And once a plug fouls, it more than likely will continue to cause grief.<br />The ignition arc can find another path to ground,and can jump as far as 1" to find it.<br />When it does,it developes a "ground-path" which normaly can't be seen, where the arc has an easier route. So do replace with new.<br />The plugs for your outboard are cheap (2 buks each or so at the local auto parts store).<br />It woudn't hurt to keep a set of spares onboard too.<br />Good luck,and tuaght tubez

 

[joeboater]

Re: Force 90 flooding

12Footer - Thanks for your response. I have burned quite a few tanks so I don't think it is the fuel itself, however, I have been running the 2-cycle oil at ~60:1 to keep from fouling out the plugs. I will be digging out the repair manual to find the carb settings spec and will start playing with the adjustment screws. All 2-strokes that I have worked on have a high-end and low-end adjustment, the Force has only one per carb. Does this control both WOT & Idle? Do this carb have a float setting for the verturi? The gap on the plugs are not adjustable and I have been replacing them way to regularly. I have an appointment with a mechanic but he backlogged for a month, (It's serious boating season here in California) so I'm trying to do what I can now.

 

[12Footer]

Re: Force 90 flooding

Idle on those carbs are adjusted at a small black plastic roller,with a screw running thru it's center, mounted on the throttle cam arm. The screw is offset,and when you <br />turn the screw,it allows you to adjust the idle. They also have a tendancy to move when the engine is running (from vibration),and you might want to locktite them down after you get them set. Just dont get any on the black roller

<br />I don't blame you for wanting to get it on the water. A month would be too long to wait for me too..<br />The float adjustment is very tricky on the tilotsen carbs. You adjust it by BENDING the the tong under the needle valve (needle valve rests on this tong).<br />It's good in that it never "runs-out" of adjustment, but a real flea-fight when it gets moved or accidentally bent out of adjustment...And that is easily done durring rebuild job.

 

[ODDD1]

Re: Force 90 flooding

Joe, any outboard running problem diagnosis starts on the first page, every time<br />1 compression test of all cylinders..engine must be mechanically healthy or no amount of tune up work will help<br />2 spark test...not talkin holding the plugs on the head an crankin it over...there is a specific air gap that the system should jump at crankin speed..any less means it must be repaired...I believe gap on your force is 7/16".<br />3now that you can assume spark and engine mechanical are ok, if you have a prob you address fuel system...supply to motor, fuel pump, carburators,setup between carbs and spark advance<br />hope this will keep you from chasing yer tail..good luck

 

[MrBo]

Re: Force 90 flooding

Gentlemen,<br /><br />I posted a problem today that I am having with my 1995 120 hp Force. It is somewhat similar. I found the procedure for adjusting the idle mixture screw to be a very difficult and I am not confident I did it correct( see the problems I had). Based on what I read in the manual though, the idle speed 700-800 RPM(in gear), should be adjusted by the throttle stop screw. Just thought I add a thought.

 

[clanton]

Re: Force 90 flooding

Set carb float, turn carb upside down, float bowl gasket surface level bend tab on float until floats sets level also. float must move freely. Metal floats may have pin hole ,leaks gas inside,become heavy runs rich. You should not mix parts from one carb to the other, jet size, needle and seat not always the same. idle needle try 3/4 turn out for starting point. The cam and roller should not touch at idle, and throttle places should be closed. Check fuel pump diaphram. I have manual,but like MrBo not always clear.