choke plate adjustment & solenoid 85hp force 1989

Karla45

Petty Officer 1st Class
Joined
Jul 12, 2009
Messages
281
got boat back from shop. Mechanic told me that he was not able to get the choke plate on the top carb to close fully but the bottom 2 close all the way. He told me adjustment is tricky on this motor. How do i fix this? I looked in manual for choke adjustments. It talks about the air horn on the carb but i do not know where the air horn is or what looks like. Did not see in daigrams. Could someone help me out on how to do adjustment so that all choke plates close?

He also told me that he thought the solenoid was weak. Could a weak battery or poor connection cause it to be weak? How can you tell if a solenoid is weak. It is still much harder to start than before.
 

Karla45

Petty Officer 1st Class
Joined
Jul 12, 2009
Messages
281
Re: choke plate adjustment & solenoid 85hp force 1989

anybody able to help out here.
 

Frank Acampora

Supreme Mariner
Joined
Jan 19, 2007
Messages
12,004
Re: choke plate adjustment & solenoid 85hp force 1989

Hi, Karla. Se Moi!

It is not really tricky to adjust choke plates on these engines and there is a little "slop" in the system.

First some terminology: Starboard is the right side of the boat and Port is the left. NOW, it doesn't matter which way we are looking at the engine, front or rear, the starboard side is always the same and port is always the same.

Now for some theory: Gasoline must be vaporized in order to burn. When an engine is cold, the gasoline does not vaporize well and there is not enough gas in the engine to vaporize either. In order to get enough vapors for the engine to fire, more gasoline must be delivered. Choking the engine by manually closing the front of the carbs does this.

On the port side of the engine very near the front of the carbs is a round rod that appears to connect all three carbs. This is the connecting rod for all three chokes. It attaches to all three levers by slotted screws.

The choke solenoid is connected to the top carb at the fitting that holds the connecting rod. the solenoid is a brass colored cylinder below and to the side of the middle carb, held to the manifold by a bent metal strap and two bolts. The solenoid is basically a large coil of wire that becomes an electromagnet when voltage is applied to it. Because of its simplicity, it is rare for it to become "weak." Most usually, the wire inside breaks or shorts and the solenoid becomes inoperable.

When you push in the ignition key, the choke solenoid pulls in the steel slug and the connecting linkage closes all three choke plates. This significantly increases manifold vacuum when cranking and allows the engine to draw in more fuel.

However, the vacuum can be so high that too much fuel is delivered, so most of the times, the choke plates have a single hole or several holes in them to reduce vacuum.

NOW: Each choke lever on the side of each carb has a return spring and the solenoid should be able to pull against all three springs. If it can not do this, the chokes will not close. If it can not do this, there are several places to check. Check the steel slug for accumulations of grease or oil that make it difficult to draw in. The slug does NOT need lubrication of any sort. Check the green wire to be certain it is not shorting against the engine or the solenoid.

Connected to the front of the carbs is the "AIRBOX." It is the rectangular metal piece with an opening on the starboard side. It is connected to the carbs by two screws at each one. Between the airbox and the front of the carbs (The airhorns) there are three gaskets. These gaskets can sometimes swell from fuel and oil absorbtion. When this happens, they MAY contact the choke levers and prevent them from moving or make it difficult for them to move. SO, without removing the airbox, check the gaskets by pushing down on the steel slug. If the levers feel like they are sticking, then simply trim excess gasket with a razor.

Now, to check the movement of the choke plates themselves: Remove the six screws in the front and remove the airbox. push down on the steel slug (Not the link, the slug itself.) with a screwdriver until it bottoms in the choke solenoid or stops. ALL three choke plates should close so that they contact the carb castings at the bottom. If they don't, then they need adjusting or the solenoid needs to be correctly positioned. The solenoid has a green wire terminal at the top side. the insulating washer on the bottom of this terminal should be within and against the bottom of the circular notch in the retaining strap or VERY close to it. (and the green wire terminal should not touch the strap, BUT it will be very close)

With the solenoid correctly positioned, the top plate should snap closed with the steel slug either bottomed in the solenoid or close to the bottom. If it does not, then the link from the slug to the top choke lever will need to be bent a bit to shorten it. You want the plate to close to within the thickness of a small slip of paper between the choke plate and the carb.

Now, with the slug held down, you check the other two choke plates. If they do not close the same as the top plate, you loosen the screws on the connecting rod and --here is where a little help comes in handy-- while you press the top plate closed, press each of the other two plates closed and tighten the screws.

Presto: The chokes are adjusted!

Re-attach the airbox and be certain the hose on the bottom is connected

Note that because of the slop in the linkage the choke plates may remain a tiny bit open when you energise the solenoid, even after adjusting. This is OK. As long as they are not significantly open while you choke the engine, it will get enough gas.

The first photo shows the choke levers on the sides of the carbs.

The second shows the round connecting rod off to the right of the red covers on a four cylinder engine. It connects two carb chokes here, but it is the same rod with the same connectors and screws as on the three cylinder engines. You can barely make out the choke solenoid since it is in a different position on the four cylinder engines and in this photo, mostly hidden by the white plastic fuel filter.

Third photo is looking in the "airhorns" of all three carbs. We can see the open choke plates and the narrowing, or venturis, of the carbs. We can see the closed butterflies in the back of the venturis. At the top of the carbs we can see the brass low speed mixture adjusting needles. The thick brass tube inside the ventui is the high speed dip tube and delivers gasoline usually only at speeds over 1500-2000 RPM. The thin brass tube within it, that goes to the top of the carb, delivers gas to the low speed circuit
 

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Karla45

Petty Officer 1st Class
Joined
Jul 12, 2009
Messages
281
Re: choke plate adjustment & solenoid 85hp force 1989

Thank you for clarification on weak choke question. I was wondering what he meant by this. Thank you so much for the details and pictures. It makes me really understand how things are supposed to work and makes things more simplistic. I will let you know how things turn out.
 

aspenrt360

Recruit
Joined
Nov 20, 2010
Messages
5
Re: choke plate adjustment & solenoid 85hp force 1989

i just want to say i think that the response you just got was awsome real good and useful info it is nice to see someone take the time to do that! just want to bring that up.
 
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