Carburator adjustment

[Michael Lang]

Hey all you carb. experts out there. Attempting final adjustments before my actual lake run ( 70 degrees here), I have a used Force 1991 70 HP with a tillotson TC111A carb. the float adjust was wrong and I corrected the float height but cannot correct the float drop because the tab is plastic and part of the molded plastic float and will break if I attempt to bend it, I am thinking that it is OK, the float drops down and rests on the main jet fuel nozzle.

I live in Utah elevation 5300 feet and my main jet is .096 and service manual lists a .090 for my elevation, do I need to change?

Any comments appreciated.

 

[MickLovin]

Re: Carburator adjustment

Not sure about the Force, but this was a spec for the float on my chrysler how far from the jet the flaot should be, I am wondering if you could get the float with brass tabs but I am not sure if they would be interchangeable from chrysler to force. Sounds like it is cold in Utah, I'm from Australia so cold isn't a problem. As I don't know the specs for your carbies, I wouldn't think it would hurt to jet them down in higher sea level situations like yours, as the Chrysler outboards are jetted down for above sea level at certain levels.
I wouldn't think the float would be a problem as it should be full most of the time, as long as it didn't stick down when it hit the jet.
As I say not sure of the specs for force, but my jets are only .096 and that's for a TC5D carb which aren't standard as the carbs I have are TC and the old carbs where WB @ .080. Also there was another post very similiar to this called "changing carb jet" have a look at that post as well.

 

[Frank Acampora]

Re: Carburator adjustment

Yes, there is a specification for float drop and no, you can not adjust the plastic tab. As long as the float itself is not hanging up on the jet, leave it. Test it by inverting the carb a couple of times and watching the float, If it drops into its normal closed position, then it will be alright when running. The float drop specification is to ensure that the float drops enough to fully open the inlet needle, not to limit its opening.


NOW: At your altitude, the air is less dense. Any internal engine is basically an air pump: The more air you pump through it, the more fuel it can burn, and the more horsepower it will make.

So with less air (and oxygen available, the engine will not only make less horsepower, but will run too rich using the sea level jet. This will lead to even less horsepower production. To Maximize the engine's potential and prevent fouled plugs, you must re-jet to the factory quoted size for your altitude.

However, the engine will still be producing less horsepower so in order to keep full throttle RPM up to factory quoted ranges, you must also reduce the prop pitch.

Yes, you can not get around it: Top speed and performance will be less than at sea level.

 

[Michael Lang]

Re: Carburator adjustment

Thanks to both Mick and Frank, your responses are very helpful, have last question regarding the TC111A carb. The iboats diagram for my model H0706X91B shows a deflector part number 819209, I am missing that part and is it needed and what was it's function?
Thanks to all.

 

[MickLovin]

Re: Carburator adjustment

Maybe Frank could tell you if it is needed, they manufacture parts that are usually needed in some form, is it worth trying to find a couple of carbies out of a wreck, then at least you have a spare set you could leave cleaned and ready to go. I have a spare set of wb carbs for my 100hp chrysler as I wanted to try a bigger carbie only problem is I have to change the flanges as well which is no biggy, and I am sort of glad I did as the TC are working better now I have finally adjusted everything correctly. Maybe it is to deflect air into the carbie?
I did notice part 24 which is your bowl screw, and it has an outlet on it, does yours and now I am wondering if it would fit mine, nice to check the bowl contents without unscrewing the bowl nut.

 

[Frank Acampora]

Re: Carburator adjustment

I have seen those 70s with the deflector--in fact, I have one. I don't know what it is but I always work on the theory that the factory would not put an added cost part onto an engine unless it was needed.

I suspect several things:
1. There is a web on the manifold blanking off about 1/3 of the hole. Since the three cylinder manifold has a goofy arrangement and a web inside to direct flow, and since the deflector is mounted at an angle, I think the deflector plate MAY be an attempts to direct and equalize airflow to all three cylinders.
2. I worked on a smaller 28 HP OMC which also had a deflector plate on the front of the carb--it would not run without it. So: the plate may also be an attempt to increase venturi depression (vacuum)

 

[pnwboat]

Re: Carburator adjustment

The deflector is there for a reason. Is this what you're missing? The piece that the red arrow is pointing at?

 

[Frank Acampora]

Re: Carburator adjustment

No, PNW. That is the cast-in baffle on the manifold. There is a stainless plate bolted to the front of the carb at a similar angle, blocking off about 1/3 of the carb inlet. As I stated above, I agree with you--- IT IS NEEDED. I just don't know the exact reason why.

 

[Michael Lang]

Re: Carburator adjustment

Thanks everyone I found the part on the net. $7.00 and 6.95 to ship. oh well I am thinking of naming my boat the money pit. went ahead and ordered it. My other half is getting fed up with my new hobby.

 

[pnwboat]

Re: Carburator adjustment

Well you know what they say.....B.O.A.T.= Break Out Another Thousand. LOL! Anytime I spend less than $100 for a repair, I feel good. Be glad you don't have to take it to a shop.